Journal articles on the topic 'Spectral wave period'
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1
Hamilton, L. J. "Methods to obtain representative surface wave spectra, illustrated for two ports of north-western Australia." Marine and Freshwater Research 48, no. 1 (1997): 43. http://dx.doi.org/10.1071/mf94220.
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Simple automatic methods of classifying surface wave spectra in terms of spectral shape are outlined and are used to examine the monthly wave climatology for the port approaches to Dampier and Port Hedland on the North West Shelf of Australia. Waves and swell at these shallow sites occur independently in three frequency bands. These correspond to low-energy long-period swell from distant sources (periods of 12 to 20 s), cyclones or energetic local storms (periods of 8 to 12 s), and local winds (periods of 4 to 8 s). Summer cyclones generate highest waves, but sea breezes are the dominant mode of wave generation. Waves and swell tend to occur episodically and independently in any month, and the peak frequency shifts during the wave generation process, so that a representative spectrum formed by simple averaging of spectra would be grossly oversmoothed. To overcome this, the monthly climatology is presented in terms of reference spectral shapes (the Ochi and Hubble 1976 North Atlantic formulations) that are most likely to occur for particular frequency bands and ranges of significant wave height. Measured spectra may then be selected as representative spectra from groupings associated with the most likely reference shapes, with further criteria such as spectral width being used to define what is typical. In some cases, the reference spectra provide good enough fits to enable them to be used directly as representative spectra.
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Aouf, Lotfi, Jean-Michel Lefèvre, and Danièle Hauser. "Assimilation of Directional Wave Spectra in the Wave Model WAM: An Impact Study from Synthetic Observations in Preparation for the SWIMSAT Satellite Mission." Journal of Atmospheric and Oceanic Technology 23, no. 3 (March 1, 2006): 448–63. http://dx.doi.org/10.1175/jtech1861.1.
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Abstract Within the framework of the Surface Waves Investigation and Monitoring from Satellite mission (SWIMSAT) proposed to the European Space Agency, an assimilation scheme has been implemented in the Wave Model (WAM) in order to estimate the impact of spectral information on wave prediction. The scheme uses an optimal interpolation and the “spectral partitioning” principle. The synthetic wave spectra are located along a SWIMSAT orbit track and are assimilated in a 4-day-period simulation. Random errors are included to simulate the uncertainties of SWIMSAT instrumentation. The sensitivity of the scheme to background and observational errors and the correlation length is examined. The assimilation impact is investigated for two cases of moderate and large errors of the first guess. The results show that the assimilation scheme works correctly and the rms errors of significant wave height, mean period, and direction are significantly reduced for both periods of analysis and forecast. The impact on significant wave height is noticeable during the period of analysis and stays efficient for 2-day forecasts. For a large error in the first guess, the impact increases and remains significant for 3-day forecasts. Statistical analysis of mean wave parameters clearly shows that the use of spectral information yields a better estimate of wave frequency, direction, and low-frequency wave height in comparison with the results based upon assimilation of wave heights only. However, total significant wave height is less sensitive to the addition of spectral information in the assimilation scheme. The use of correlation length depending on the latitude of grid points leads to a better spread of incremental observations and, hence, to better skills in terms of the rms errors of mean wave parameters. The use of several wavelength cutoffs concerning the SWIMSAT synthetic wave spectra suggests that the “assimilation index” of mean wave parameters decreases with the increasing wavelength cutoff.
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Guedes Soares, C., and M. C. Nolasco. "Spectral Modeling of Sea States With Multiple Wave Systems." Journal of Offshore Mechanics and Arctic Engineering 114, no. 4 (November 1, 1992): 278–84. http://dx.doi.org/10.1115/1.2919981.
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The spectral models of individual wave systems have one peak and are described by theoretical models that have gained general acceptance. This work deals with sea states with more than one wave system, leading to spectral models with two or more peaks. Use is made of spectra derived from measurements off the Portuguese Coast and data is provided as to their probability of occurrence as well as about the dependence of the spectral parameters on the significant wave height and peak period. It is shown that wind-dominated and swell-dominated two-peaked spectra tend to occur in different areas of the scatter diagram. The spectral parameters of the two-peaked spectra show little correlation with significant wave height and peak period.
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Nair, M. Anjali, and V. Sanil Kumar. "Wave spectral shapes in the coastal waters based on measured data off Karwar on the western coast of India." Ocean Science 13, no. 3 (May 3, 2017): 365–78. http://dx.doi.org/10.5194/os-13-365-2017.
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Abstract. An understanding of the wave spectral shapes is of primary importance for the design of marine facilities. In this paper, the wave spectra collected from January 2011 to December 2015 in the coastal waters of the eastern Arabian Sea using the moored directional waverider buoy are examined to determine the temporal variations in the wave spectral shape. Over an annual cycle for 31.15 % of the time, the peak frequency is between 0.08 and 0.10 Hz; the significant wave height is also relatively high (∼ 1.55 m) for waves in this class. The slope of the high-frequency tail of the monthly average wave spectra is high during the Indian summer monsoon period (June–September) compared to other months, and it increases with an increase in significant wave height. There is not much interannual variation in the slope for swell-dominated spectra during the monsoon, while in the non-monsoon period when wind-seas have a high level of influence, the slope varies significantly. Since the exponent of the high-frequency part of the wave spectrum is within the range of −4 to −3 during the monsoon period, the Donelan spectrum shows a better fit for the high-frequency part of the wave spectra in monsoon months compared to other months.
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Li, Jian-Guo, and Martin Holt. "Comparison of Envisat ASAR Ocean Wave Spectra with Buoy and Altimeter Data via a Wave Model." Journal of Atmospheric and Oceanic Technology 26, no. 3 (March 1, 2009): 593–614. http://dx.doi.org/10.1175/2008jtecho529.1.
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Abstract The Advanced Synthetic Aperture Radar (ASAR) on board the Envisat satellite is an important resource for observation of global ocean surface wave spectra. However, assessment of this valuable dataset is not straightforward as a result of a lack of other independent ocean wave spectral observations. The radar altimeter (RA-2) on board the same satellite measures ocean wave height at the same time as the ASAR but at a location about 200 km distant. A small number of moored buoys produce one-dimensional (1D) ocean wave spectra but few ASAR spectra fall on the buoy positions in a given period. Indirect comparison of the Envisat ASAR 2D wave spectra with the RA-2 wave heights and 1D spectra of three selected buoys from July 2004 to February 2006 is facilitated by a wave model, which provides coherent spatial and temporal links between these observations. In addition to the conventional significant wave height (SWH), four spectral subrange wave heights (SRWHs) are used to illustrate the spectral characteristics of these observations. A comparison of three Envisat ASAR 2D spectra with the closest model and buoy spectra is also attempted to illustrate the qualities of these different observations and to demonstrate the restrictions to their direct comparison. Results indicate that these three independent observations are in good agreement in terms of SWH, though the Envisat ASAR shows the largest variance. Comparison of SRWHs indicates that the ASAR spectra agree well with buoy and model in moderately long waves, but the ASAR instrument does not resolve high-frequency waves, especially along the satellite track.
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Ern, M., P. Preusse, M. Krebsbach, M. G. Mlynczak, and J. M. Russell III. "Equatorial wave analysis from SABER and ECMWF temperatures." Atmospheric Chemistry and Physics Discussions 7, no. 4 (August 8, 2007): 11685–723. http://dx.doi.org/10.5194/acpd-7-11685-2007.
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Abstract. Equatorial planetary scale wave modes such as Kelvin waves or Rossby-gravity waves are excited by convective processes in the troposphere. In this paper an analysis for these and other equatorial wave modes is carried out with special focus on the stratosphere using temperature data from the SABER instrument as well as ECMWF temperatures. Space-time spectra of symmetric and antisymmetric spectral power are derived to separate the different equatorial wave types and the contribution of gravity waves is determined from the spectral background of the space-time spectra. Both gravity waves and equatorial planetary scale wave modes are main drivers of the quasi-biennial oscillation (QBO) in the stratosphere. Temperature variances attributed to the different wave types are calculated for the period from February 2002 until March 2006 and compared to previous findings. A comparison between SABER and ECMWF wave analyses shows that in the lower stratosphere SABER and ECMWF spectra and temperature variances agree remarkably well while in the upper stratosphere ECMWF tends to overestimate Kelvin wave components. Gravity wave variances are partly reproduced by ECMWF but have a significant low-bias. A case study for the time period of the SCOUT-O3 tropical aircraft measurement campaign in Darwin/Australia (in November and December 2005) is performed and we find that in the lower stratosphere also the longitude-time distribution of the Kelvin waves is correctly reproduced by ECMWF.
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Ern, M., P. Preusse, M. Krebsbach, M. G. Mlynczak, and J. M. Russell. "Equatorial wave analysis from SABER and ECMWF temperatures." Atmospheric Chemistry and Physics 8, no. 4 (February 21, 2008): 845–69. http://dx.doi.org/10.5194/acp-8-845-2008.
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Abstract. Equatorial planetary scale wave modes such as Kelvin waves or Rossby-gravity waves are excited by convective processes in the troposphere. In this paper an analysis for these and other equatorial wave modes is carried out with special focus on the stratosphere using temperature data from the SABER satellite instrument as well as ECMWF temperatures. Space-time spectra of symmetric and antisymmetric spectral power are derived to separate the different equatorial wave types and the contribution of gravity waves is determined from the spectral background of the space-time spectra. Both gravity waves and equatorial planetary scale wave modes are main drivers of the quasi-biennial oscillation (QBO) in the stratosphere. Temperature variances attributed to the different wave types are calculated for the period from February 2002 until March 2006 and compared to previous findings. A comparison between SABER and ECMWF wave analyses shows that in the lower stratosphere SABER and ECMWF spectra and temperature variances agree remarkably well while in the upper stratosphere ECMWF tends to overestimate Kelvin wave components. Gravity wave variances are partly reproduced by ECMWF but have a significant low-bias. For the examples of a QBO westerly phase (October–December 2004) and a QBO easterly phase (November/December 2005, period of the SCOUT-O3 tropical aircraft campaign in Darwin/Australia) in the lower stratosphere we find qualitatively good agreement between SABER and ECMWF in the longitude-time distribution of Kelvin, Rossby (n=1), and Rossby-gravity waves.
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Ponce de León, Sonia, and C. Guedes Soares. "Extreme Waves in the Agulhas Current Region Inferred from SAR Wave Spectra and the SWAN Model." Journal of Marine Science and Engineering 9, no. 2 (February 2, 2021): 153. http://dx.doi.org/10.3390/jmse9020153.
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The influence of the Agulhas Current on the wave field is investigated. The study is conducted by performing high resolution spectral wave model simulations with and without ocean currents. The validation of the numerical simulations is performed for the Significant Wave Height (Hs) using all possible satellite altimetry data available in the study region for a winter period of 2018. Wave spectra and extreme waves parameters are examined in places where waves and current are aligned in the Agulhas Current. Sentinel-1 (S1) wave mode Synthetic Aperture Radar (SAR) spectra are used to estimate the composites of the Hs and BFI (Benjamin–Feir Index). SAR computed BFI and Hs were compared with the respective composites obtained from the Simulating Waves Nearshore (SWAN) model. From the Hs composites using SAR data and modeled data, it can be concluded that the Hs maxima values are distributed in the Agulhas Current Retroflection (ACR) and also in the southern limit of the domain that is affected by the strong circumpolar winds around Antarctic. In addition, the BFI composites exhibit the highest values in the ACR and some few values are observed in the southern border as occurred with the Hs. The results of this study indicate that there is direct correlation between the Agulhas Current strength, the Hs and the BFI. It was found that the modeled directional wave spectra are broadened when the ocean current is considered in the simulation. The analysis of the modeled wave spectra is performed over eddies, rings and meanders in the Agulhas Current region. The transformation of the wave spectra due to current refraction is discussed based on the numerical simulations. The effect of the Agulhas Current on the spectral shape is explored. The spectral wave energy grows when the wave and the current are aligned, resulting in peaked, elongated and widened spectra. A decrease of the peak period was observed before the occurrence of maximum values of BFI, which characterize abnormal sea states.
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Álvarez, Enrique, and Ramón Plaza. "Existence and spectral instability of bounded spatially periodic traveling waves for scalar viscous balance laws." Quarterly of Applied Mathematics 79, no. 3 (March 17, 2021): 493–544. http://dx.doi.org/10.1090/qam/1591.
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This paper studies both existence and spectral stability properties of bounded spatially periodic traveling wave solutions to a large class of scalar viscous balance laws in one space dimension with a reaction function of monostable or Fisher-KPP type. Under suitable structural assumptions, it is shown that this class of equations underlies two families of periodic waves. The first family consists of small amplitude waves with finite fundamental period which emerge from a Hopf bifurcation around a critical value of the wave speed. The second family pertains to arbitrarily large period waves which arise from a homoclinic bifurcation and tend to a limiting traveling (homoclinic) pulse when their fundamental period tends to infinity. For both families, it is shown that the Floquet (continuous) spectrum of the linearization around the periodic waves intersects the unstable half plane of complex values with positive real part, a property known as spectral instability. For that purpose, in the case of small-amplitude waves it is proved that the spectrum of the linearized operator around the wave can be approximated by that of a constant coefficient operator around the zero solution and determined by a dispersion relation which intersects the unstable complex half plane. In the case of large period waves, we verify that the family satisfies the assumptions of the seminal result by Gardner (Spectral analysis of long wavelength periodic waves and applications, J. Reine Angew. Math. 491 (1997), 149–181) of convergence of periodic spectra in the infinite-period limit to that of the underlying homoclinic wave, which is unstable. A few examples are discussed.
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Nguyen, Thu-Ha, Bas Hofland, Vu Dan Chinh, and Marcel Stive. "Wave Overtopping Discharge for Very Gently Sloping Foreshores." Water 12, no. 6 (June 13, 2020): 1695. http://dx.doi.org/10.3390/w12061695.
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The spectral wave period T m − 1 , 0 at the toe of sea-dikes is a crucial parameter to predict wave overtopping discharge over sea-dikes. It is known from literature that this period quickly increases when waves reach shallow foreshores; however, sometimes the assumption is made that the wave period remains constant from offshore to near-shore, leading to an underestimation of the near-shore wave period. Several formulae have been proposed to resolve the underestimation of wave overtopping discharges for very shallow foreshores. These corrective formulations confirm the tendency of underestimating the overtopping discharges over a very gently sloping foreshore but are not validated for foreshore slopes gentler than 1:500. The “equivalent slope” method based on a recent study is inappropriate for these very gently sloping foreshores due to the breaker parameter being much smaller than seven. This study proposes an extension of the correction and finds that spectral wave periods can reach values two times those offshore.
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Farkas, Andrea, Joško Parunov, and Marko Katalinić. "Wave Statistics for the Middle Adriatic Sea." Journal of Maritime & Transportation Science 52, no. 1 (December 2016): 33–47. http://dx.doi.org/10.18048/2016.52.02.
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The paper presents the methodology and results of the sea state statistics development for the middle Adriatic Sea. The study is based on the World Waves Atlas containing data of sea states in the Adriatic Sea calibrated using different satellite missions and numerical wave model simulations during the period of past 23 years. Wave scatter diagram and wave rose at the location in the middle Adriatic Sea are derived from the data. The 3-parametric Weibull distribution and the log-normal distribution for significant wave height and peak spectral periods respectively, are fitted through the data in the World Waves Atlas. Based on available data, the relation between wind speed and wave height is established by regression analysis. Comparison of the relationship between the significant wave height and peak spectral period is performed between the data from the World Waves Atlas and the Tabain’s wave spectrum, frequently used for sea states in the Adriatic Sea. Finally, the most probable extreme sea states for different return periods are calculated and results are compared with another relevant study for the long-term prediction of sea states in the Adriatic Sea.
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Jamieson, Wayne W., Etienne P. D. Mansard, and Geoffrey R. Mogridge. "IRREGULAR WAVE LOADING ON A CONICAL STRUCTURE." Coastal Engineering Proceedings 1, no. 21 (January 29, 1988): 167. http://dx.doi.org/10.9753/icce.v21.167.
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The horizontal forces, vertical forces and overturning moments exerted by waves on a fixed model of a 45" conical structure are presented. Irregular wave loading tests were conducted for a range of conditions described by base diameter on peak period wave length D/Lp from 0.31 to 1.76, water depth on peak period wave length h/Lp from 0.11 to 0.63, and significant wave height on peak period wave length Hm./Lp up to 0.07. Time series records, spectral densities and transfer functions for the irregular wave loading tests are used to illustrate the nonlinear nature of the measured wave loads. In most cases, similar trends in wave loading were observed for irregular and regular wave tests. For deep-water waves, the irregular and regular force measurements showed spectral peaks at the second harmonic of the wave frequency even though the waves themselves had relatively small second-order components. However, unlike the regular wave loading results, the fundamental spectral peak frequency for the irregular wave forces occurred at a frequency considerably lower than the peak frequency of the waves. Although linear diffraction theory provided a reasonable estimate of the wave forces for waves of low steepness, larger deviations were often present for higher wave steepness results. Comparison of theory and experiment for overturning moments was generally very poor for most wave conditions.
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MISHRA, S. K. "Barotropic spectral modeling of non-linear interaction For transient waves in tropical easterly jet." MAUSAM 41, no. 2 (February 22, 2022): 100–109. http://dx.doi.org/10.54302/mausam.v41i2.2548.
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The wave-zonal flow and wave-wave interactions are studied over the sphere for the initial single linear barotropic unstable mode of the mean monsoon tropical easterly jet at 100 mb. The non-divergent barotropic global spectral model with truncation N=20 and M=40 is integrated for 120 days for the study. It is found that the wave-zonal flow interaction leads to an oscillation with a period of 35 days in the wave kinetic energy and enstrophy. The relation between the zonal angular momentum transport and growth-decay cycle of the wave is explored. The wave-wave interaction is responsible for the variation in the period of low frequency oscillation between 25&35 days. The mean kinetic energy and enstrophy spectra, and wave-wave interaction in the wave number domain are computed and their role in the non-linear evolution of the waves is discussed.
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Goda, Yoshimi. "Numerical Simulation of Ocean Waves for Statistical Analysis." Marine Technology Society Journal 33, no. 3 (January 1, 1999): 5–14. http://dx.doi.org/10.4031/mtsj.33.3.2.
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A review is made on the numerical simulation technique of ocean surface wave profiles under a given spectral form. Two standard frequency spectral functions are given, and the statistical characteristics of wave heights and periods are examined from a large number of simulated wave profiles. The effects of spectral shapes on the representative heights and periods are presented in tabular forms. The statistical variability of significant wave height, mean period, and others obtained from one record are shown to be inversely proportional to the square root of the number of waves in a record. From the spatial simulation of wave profiles, the length and height of wave crests are defined and their statistical characteristics are examined. Comments are made on the preparation of the wave generator control signals for 3-D wave basins. A possibility of randomly varying infragravity wave motion is discussed with an example.
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Risandi, J., T. Solihuddin, TL Kepel, A. Daulat, A. Heriati, E. Mustikasari, and R. Hidayat. "Low-cost investigation of wave dynamics across low energy reef environments in Indonesia." IOP Conference Series: Earth and Environmental Science 1119, no. 1 (December 1, 2022): 012033. http://dx.doi.org/10.1088/1755-1315/1119/1/012033.
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Abstract The interaction between offshore waves and complex reef bottom profiles determines the hydrodynamic processes within the reef beaches, for instance, Sea-Swell (SS) wave dissipation, Infragravity (IG) wave generation as well as wave-induced currents and setups. These hydrodynamics phenomena are important to several ecological processes and control the associated shoreline erosion and flooding. Hence, a good understanding of the dynamics is needed that wave observations are challenging and expensive otherwise. Here we present a short term (12 hours) investigation of non-directional spectral waves using a series of HOBO pressure sensors. Six pressure sensors were deployed at 3 locations along the fringing reefs of Tunda Island, Banten Province - Indonesia. The wave spectra were estimated from the surface water fluctuations using linear wave theory for each hourly burst data. During observation, the Tunda waters were calm with significant wave heights were less than 10 cm with peak wave periods of ∼12 s at all sites. Despite the short period measurement due to memory issue, the result demonstrated the ability of HOBO pressure sensors to measure non-directional wave spectra at shallow water.
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Rodrı´guez, Germa´n, C. Guedes Soares, and Mercedes Pacheco. "Wave Period Distribution in Mixed Sea-States." Journal of Offshore Mechanics and Arctic Engineering 126, no. 1 (February 1, 2004): 105–12. http://dx.doi.org/10.1115/1.1643387.
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The statistical distribution of zero up-crossing wave periods in Gaussian mixed sea-states is examined by using numerically simulated data. Nine different kinds of bimodal spectra are used to analyze the effects of the relative energy ratio and the peak frequency separation between the low- and high-frequency wave fields on the wave period distribution. Observed results are compared with predictions given by probabilistic models suitable for practical applications. Numerical results reveal a different behavior for low- and high-period bands. Furthermore, comparisons of the empirical data with some probabilistic models often used in practice shows that none of these models is able to characterize adequately all the cases of combined sea-states examined. In fact, they might be used only in the case of wind-sea dominated sea-states with small separation between spectral frequency peaks. However, a model recently proposed by Myrhaug and Slaattelid [1] represents adequately the observed distributions of wave period.
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Rathje, Ellen M., Kenneth H. Stokoe, and Brent Rosenblad. "Strong Motion Station Characterization and Site Effects during the 1999 Earthquakes in Turkey." Earthquake Spectra 19, no. 3 (August 2003): 653–75. http://dx.doi.org/10.1193/1.1596212.
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The 1999 Kocaeli and Duzce earthquakes in Turkey generated a moderate amount of strong ground motion data. This paper describes the shear-wave velocity profiles measured at a number of strong motion stations in Turkey using the spectral-analysis-of-surface-waves (SASW) method. The shear-wave velocity profiles from SASW testing compare well with deeper profiles developed by microtremor surface wave inversion, but SASW provides more shear-wave velocity resolution near the ground surface. The developed shear-wave velocity profiles are used to define site classifications for each station. For the Kocaeli earthquake, event-specific attenuation relationships are developed. These relationships show considerable amplification of peak ground acceleration and spectral acceleration (at a period of 0.3 s) at deep soil sites in the far field, but no amplification in the near-fault region. For spectral accelerations at longer spectral periods (1.0 and 2.0 s), amplification is indicated in both the near field and far field. Amplification factors derived from the Kocaeli earthquake strong motion data are generally larger than those used in current attenuation relationships and building codes. The short-period amplification factors derived from the regression decrease with increasing rock motion intensity (PGArock), and the derived long-period amplification factors increase with increasing PGArock. These trends are most likely due to soil nonlinearity. The increase in long-period amplification factors with PGArock is not taken into account in current building codes.
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Ponce de León, Sonia, and C. Guedes Soares. "Numerical Modelling of the Effects of the Gulf Stream on the Wave Characteristics." Journal of Marine Science and Engineering 9, no. 1 (January 4, 2021): 42. http://dx.doi.org/10.3390/jmse9010042.
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The influence of the Gulf Stream on the wind wave characteristics is investigated. Wave–current interaction inside the current field can result in significant inhomogeneities of the wave field that change the wave spectrum and wave statistics. This study relies on regional realistic simulations using high resolution in time, space and in the spectral space that allow to solve small scale features of the order of 5 km. Wave model simulations are performed with and without ocean currents to understand the impact of the Gulf Stream. Modelled wave spectra are examined along the main axis of the Gulf Stream, and also along a transect that crosses the current. The behavior of significant wave height (Hs), the current speed, as well as the mean wave propagation and the current direction are analyzed at the selected transect locations. It is shown that inside the current the spectral wave energy grows if the wave and the current are aligned and opposed which result in a very peaked and elongated spectrum. The Gulf Stream causes a widening of the spectrum angular distribution. The results indicate that the Hs increases with the current velocity once the waves are inside the Gulf Stream. Most of the time, waves travelled in opposite direction to the current that flows from the SW to the NE, which could explain why inside the Gulf Stream waves are high. The validation of the numerical simulations is performed for Hs using different wave buoy data available in the study region for the winter period of 2019. In addition, one-dimensional wave spectra measured by an NDBC (National Data Buoy Center) wave buoy are compared with the WAM (Wave Advanced Modeling) modelled 1d spectra showing a good correlation. Accounting for ocean currents improves the quality of the simulated results, which is more realistic than only considering waves.
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Lee, Uk-Jae, Dong-Hui Ko, Hong-Yeon Cho, and Nam-Sun Oh. "Correlation Analysis between Wave Parameters using Wave Data Observed in HeMOSU-1&2." Journal of Korean Society of Coastal and Ocean Engineers 33, no. 4 (August 31, 2021): 139–47. http://dx.doi.org/10.9765/kscoe.2021.33.4.139.
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In this study, waves were defined using the water surface elevation data observed from the HeMOSU-1 and 2 marine meteorological observation towers installed on the west coast of Korea, and correlation analysis was performed between wave parameters. The wave height and wave period were determined using the wave-train analysis method and the wave spectrum analysis method, and the relationship between the wave parameters was calculated and compared with the previous study. In the relation between representative wave heights, most of the correlation coefficients between waves showed a difference of less than 0.1% in error rate compared to the previous study, and the maximum wave height showed a difference of up to 29%. In addition, as a result of the correlation analysis between the wave periods, the peak period was estimated to be abnormally large at rates of 2.5% and 1.3% in HeMOSU-1&2, respectively, due to the effect of the bimodal spectrum that occurs when the spectral energy density is small.
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Oh, Jung-Eun, Weon-Mu Jeong, Yeon S. Chang, and Sang-Ho Oh. "On the Separation Period Discriminating Gravity and Infragravity Waves off Gyeongpo Beach, Korea." Journal of Marine Science and Engineering 8, no. 3 (March 3, 2020): 167. http://dx.doi.org/10.3390/jmse8030167.
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Although there have been a number of studies investigating fundamental characteristics of infragravity waves in coastal zones, a proper method of deciding period ranges that are associated with gravity or infragravity waves remains uncertain. In this study, we proposed an empirical method of separating spectral energies of gravity and infragravity waves by analyzing the wave observation data acquired off Gyeongpo beach on the Korean east coast. The fundamental principle of the suggested method is to represent the separation period discriminating gravity and infragravity waves as a function of the significant wave period, rather than a fixed value that was conventionally applied in previous studies. As a consequence of using the new method, the relationships between heights and periods of gravity and infragravity waves were more clearly identified.
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Zhuo, Yuru, and Hiroo Kanamori. "Regional variation of the short-period (1 to 10 second) source spectrum." Bulletin of the Seismological Society of America 77, no. 2 (April 1, 1987): 514–29. http://dx.doi.org/10.1785/bssa0770020514.
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Abstract We determined m^b, the body-wave magnitude calculated from the maximum amplitude of short-period P waves, of 38 large earthquakes in various tectonic provinces. The data are divided into three groups: group 1 (subduction-zone thrust events); group 2 (nonsubduction-zone dip-slip and oblique-slip events); and group 3 (strike-slip events). Groups 2 and 3 include intraplate earthquakes. Comparison of m^b values for these three groups of events suggests that the source spectral amplitudes of intraplate events at a period of about 1.4 sec is 2 to 5 times larger than those of subduction-zone events with the same Mw. We also determined the source spectra of 28 large earthquakes (Mw = 6.5 to 7.7) directly from Global Digital Seismographic Network (GDSN) data, over a period range from 1 to 10 sec. At periods from 1 to 2 sec, the source spectral amplitudes of intraplate earthquakes are 2 to 4 times larger than those of subduction-zone events with the same Mw. The difference decreases as the period increases to 10 sec.
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Madsen, Ole Secher, Ying-Keung Poon, and Hans C. Graber. "SPECTRAL WAVE ATTENUATION BY BOTTOM FRICTION: THEORY." Coastal Engineering Proceedings 1, no. 21 (January 29, 1988): 34. http://dx.doi.org/10.9753/icce.v21.34.
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Based on the linearized form of the boundary layer equations and a simple eddy viscosity formulation of shear stress, the turbulent bottom boundary layer flow is obtained for a wave motion specified by its directional spectrum. Closure is obtained by requiring the solution to reduce, in the limit, to that of a simple harmonic wave. The resulting dissipation is obtained in spectral form with a single friction factor determined from knowledge of the bottom roughness and an equivalent monochromatic wave having the same root-mean-square near-bottom orbital velocity and excursion amplitude as the specified wave spectrum. The total spectral dissipation rate is obtained by integration and compared with the average dissipation obtained from a model considering the statistics of individual waves defined by their maximum orbital velocity and zero-crossing period. The agreement between the two different evaluations of total spectral dissipation supports the validity of the spectral dissipation model.
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Scott, Julian F. "Wave turbulence in a rotating channel." Journal of Fluid Mechanics 741 (February 13, 2014): 316–49. http://dx.doi.org/10.1017/jfm.2013.652.
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AbstractThis paper describes wave-turbulence closure and its consequences for rapidly rotating (i.e. small Rossby number) turbulence confined by two infinite, parallel walls perpendicular to the rotation axis. Expressing the flow as a combination of inertial waveguide modes leads to a spectral matrix, whose diagonal elements express the distribution of energy over modes and whose off-diagonal elements represent correlations between modes of different orders. In preparation for wave-turbulence closure, the flow is decomposed into two-dimensional and wave components. The former is found to evolve as if it were a classical, two-dimensional, non-rotating flow, but with wall friction due to Ekman pumping by the boundary layers. Evolution equations for the wave-component elements of the spectral matrix are derived using a wave-turbulence approach. Detailed analysis of these equations shows that, surprisingly, the two-dimensional component has no effect on wave-component energetics. As expected for wave turbulence, energy transfer between wave modes is via resonant triads and takes place at times $O(\varepsilon ^{-2})$ multiples of the rotational period, where $\varepsilon $ is the Rossby number. Despite playing no role in wave-mode energetics, the two-dimensional component produces decay of the off-diagonal elements of the spectral matrix on a time scale that is small compared with $O(\varepsilon ^{-2})$ rotation periods. There are thus three asymptotically distinct stages in the evolution of the turbulence in the limit of small Rossby number: the two-dimensional flow begins to evolve at the usual large-eddy turnover time scale ($O(\varepsilon ^{-1})$ multiples of the rotation period) and continues to develop thereafter. This is followed by decorrelation of different wave orders and finally evolution of the wave energy spectra due to resonant interactions.
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Wright, D. M., T. K. Yeoman, L. J. Baddeley, J. A. Davies, R. S. Dhillon, M. Lester, S. E. Milan, and E. E. Woodfield. "High resolution observations of spectral width features associatedwith ULF wave signatures in artificial HF radar backscatter." Annales Geophysicae 22, no. 1 (January 1, 2004): 169–82. http://dx.doi.org/10.5194/angeo-22-169-2004.
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Abstract. The EISCAT high power heating facility at Tromsø, northern Norway, has been utilised to generate artificial radar backscatter in the fields of view of the CUTLASS HF radars. It has been demonstrated that this technique offers a means of making very accurate and high resolution observations of naturally occurring ULF waves. During such experiments, the usually narrow radar spectral widths associated with artificial irregularities increase at times when small scale-sized (high m-number) ULF waves are observed. Possible mechanisms by which these particle-driven high-m waves may modify the observed spectral widths have been investigated. The results are found to be consistent with Pc1 (ion-cyclotron) wave activity, causing aliasing of the radar spectra, in agreement with previous modelling work. The observations also support recent suggestions that Pc1 waves may be modulated by the action of longer period ULF standing waves, which are simultaneously detected on the magnetospheric field lines. Drifting ring current protons with energies of ∼ 10keV are indicated as a common plasma source population for both wave types. Key words. Magnetospheric physics (MHD waves and instabilities) – Space plasma physics (wave-particle interactions) – Ionosphere (active experiments)
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Jadhav, Ranjit S., and Qin Chen. "FIELD INVESTIGATION OF WAVE DISSIPATION OVER SALT MARSH VEGETATION DURING TROPICAL CYCLONE." Coastal Engineering Proceedings 1, no. 33 (October 25, 2012): 41. http://dx.doi.org/10.9753/icce.v33.waves.41.
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Wave data were measured along a 28 m transect using 3 pressure transducers over a 2-day period during a tropical storm. The tropical storm force winds produced waves up to 0.4 m high (zero-moment) that propagated over vegetation of Spartina alterniflora submerged under a surge of over 1 m above the marsh floor. Measured wave heights, energy losses between gages and spectral energy dissipation models of rigid vegetation were utilized to estimate wave height decay rates, integral and frequency-dependent bulk drag coefficients, and frequency distribution of energy dissipation induced by the vegetation. Measurements showed that incident waves attenuated exponentially over the vegetation. The exponential wave height decay rate decreased as Reynolds number increased. The swell was observed to decay at a slower rate than the wind sea regardless of the wave height. The linear spatial wave height reduction rate increased from 1.5% to 4% /m as incident wave height decreased. The bulk drag coefficient estimated from the field measurement decreased with increasing Reynolds and Keulegan-Carpenter numbers. The energy dissipation varied across the frequency scales with the largest magnitude observed near the spectral peaks, above which the dissipation gradually decreased. The wave energy dissipation did not linearly follow the incident energy, and the degree of non-linearity varied with the frequency. For a given spectrum, the frequency-distributed drag coefficient increased gradually up to the peak frequency and remained approximately at a stable value at the higher frequencies. This spectral variation was parameterized by introducing a frequency-dependent velocity attenuation parameter inside the canopy. The spectral drag coefficient is shown to predict the distribution of energy dissipation with more accuracy than the integral coefficients, which results in a more accurate prediction of the mean wave period and spectral width of a wave field with vegetation.
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Ellenson, Ashley, and H. Tuba Özkan-Haller. "Predicting Large Ocean Wave Events Characterized by Bimodal Energy Spectra in the Presence of a Low-Level Southerly Wind Feature." Weather and Forecasting 33, no. 2 (March 19, 2018): 479–99. http://dx.doi.org/10.1175/waf-d-17-0035.1.
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Abstract Three large wave events are simulated with WaveWatch III using different wind inputs and physics packages. The modeled output, including spectral shape and bulk parameter time series, are compared with National Data Buoy Center buoy observations offshore of Newport, Oregon. The atmospheric conditions that generate these large waves include a strong southerly wind along with a distant cyclone. The energetic contributions of these simultaneously occurring atmospheric features result in a wave field characterized by bimodal energy spectra for two events and unimodal energy spectra for the third event. The analysis of model output evaluates bulk parameter time series of significant wave height, mean period, and mean wave direction derived from partitioned energy spectra. A consistent underestimation in wave energy approaching from the southwestern direction is found for the output associated with all model configurations. This wave energy is generated by the southerly wind. An overestimation in swell energy approaching from the northwest is also found for all model configurations. The model configuration that most accurately reproduces the southerly wave energy results in the best performance for the overall bulk parameters.
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Holthuijsen, Leo H., and Nico Booij. "A GRID MODEL FOR SHALLOW WATER WAVES." Coastal Engineering Proceedings 1, no. 20 (January 29, 1986): 20. http://dx.doi.org/10.9753/icce.v20.20.
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Waves in coastal regions can be affected by the bottom, by currents and by the local wind. The traditional approach in numerical modelling of these waves is to compute the wave propagation with so-called wave rays for mono-chromatic waves (one constant period and one deep water direction) and to supplement this with computations of bottom dissipation. This approach has two important disadvantages. Firstly, spectral computations, e.g. to determine a varying mean wave period or varying shortcrestedness, would be rather inefficient in this approach. Secondly, interpretation of the results of the refraction computations is usually cumbersome because of crossing wave rays. The model presented here has been designed to correct these shortcomings: the computations are carried out efficiently for a large number of wave components and the effects of currents, bottom friction, local wind and wave breaking are added. This requires the exploitation of the concept of the spectral action balance equation and numerical wave propagation on a grid rather than along wave rays. The model has been in operation for problems varying from locally generated waves over tidal flats to swell penetration into Norwegian fjords. A comparison with extensive measurements is described for young swell under high wind penetrating the Rhine estuary.
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Lepore, Simone, and Marek Grad. "Relation between ocean wave activity and wavefield of the ambient noise recorded in northern Poland." Journal of Seismology 24, no. 6 (November 4, 2020): 1075–94. http://dx.doi.org/10.1007/s10950-020-09963-y.
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AbstractThe temporal and spatial variations of the wavefield of ambient noise recorded at ‘13 BB star’ array located in northern Poland were related to the activity of high, long-period ocean waves generated by strong storms in the Northern Indian Ocean, the Atlantic Ocean, and the Northern Pacific Ocean between 2013 and 2016. Once pre-processed, the raw noise records in time- and frequency-domains, and spectral analysis and high-resolution three-component beamforming techniques were applied to the broadband noise data. The power spectral density was analysed to quantify the noise wavefield, observing the primary (0.04–0.1 Hz) microseism peak and the splitting of the secondary microseism into long-period (0.2–0.3 Hz) and short-period (0.3–0.8 Hz) peaks. The beam-power analysis allowed to determine the changes in the azimuth of noise sources and the velocity of surface waves. The significant wave height, obtained by combining observed data and forecast model results for wave height and period, was analysed to characterise ocean wave activity during strong storms. The comparison of wave activity and beam-power led to distinguish the sources of Rayleigh and Love waves associated to long-period microseisms, of short-period microseisms, and of primary microseisms. High, long-period ocean waves hitting the coastline were found to be the main source of noise wavefield. The source of long-period microseisms was correlated to such waves in the open sea able to reach the shore, whereas the source of primary microseisms was tied to waves interacting with the seafloor very close to the coastlines. The source of short-period microseisms was attributed to strong storms constituted of short-period waves not reaching the coast.
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Reichert, Robert, Bernd Kaifler, Natalie Kaifler, Markus Rapp, Pierre-Dominique Pautet, Michael J. Taylor, Alexander Kozlovsky, Mark Lester, and Rigel Kivi. "Retrieval of intrinsic mesospheric gravity wave parameters using lidar and airglow temperature and meteor radar wind data." Atmospheric Measurement Techniques 12, no. 11 (November 19, 2019): 5997–6015. http://dx.doi.org/10.5194/amt-12-5997-2019.
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Abstract. We analyse gravity waves in the upper-mesosphere, lower-thermosphere region from high-resolution temperature variations measured by the Rayleigh lidar and OH temperature mapper. From this combination of instruments, aided by meteor radar wind data, the full set of ground-relative and intrinsic gravity wave parameters are derived by means of the novel WAPITI (Wavelet Analysis and Phase line IdenTIfication) method. This WAPITI tool decomposes the gravity wave field into its spectral component while preserving the temporal resolution, allowing us to identify and study the evolution of gravity wave packets in the varying backgrounds. We describe WAPITI and demonstrate its capabilities for the large-amplitude gravity wave event on 16–17 December 2015 observed at Sodankylä, Finland, during the GW-LCYCLE-II (Gravity Wave Life Cycle Experiment) field campaign. We present horizontal and vertical wavelengths, phase velocities, propagation directions and intrinsic periods including uncertainties. The results are discussed for three main spectral regions, representing small-, medium- and large-period gravity waves. We observe a complex superposition of gravity waves at different scales, partly generated by gravity wave breaking, evolving in accordance with a vertically and presumably also horizontally sheared wind.
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Sanil Kumar, V., and M. Anjali Nair. "Inter-annual variations in wave spectral characteristics at a location off the central west coast of India." Annales Geophysicae 33, no. 2 (February 3, 2015): 159–67. http://dx.doi.org/10.5194/angeo-33-159-2015.
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Abstract. The inter-annual variations in wave spectrum are examined based on the wave data measured at 9 m water depth off the central west coast of India from 2009 to 2012 using a wave rider buoy. The temporal variation of the spectral energy density over a calendar year indicates similar variation in all the four years studied. The inter-annual variations in wave spectrum are observed in all months with larger variations during January to February, May and October to November due to the changes in wind-sea. The seasonal average wave spectrum during the monsoon (June–September) is single-peaked and the swell component is high in 2011 compared to other years. The annual averaged wave spectrum had higher peak energy during 2011 due to the higher spectral energy present during the monsoon period. During the non-monsoon period, two peaks are predominantly observed in the wave spectra; with the average peak at 0.07 Hz corresponding to the swells from the Indian Ocean and another at 0.17 Hz due to the local wind field.
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Murphy, J. R., B. W. Barker, and A. O'Donnell. "Network-averaged teleseismic P-wave spectra for underground explosions. Part I. Definitions and examples." Bulletin of the Seismological Society of America 79, no. 1 (February 1, 1989): 141–55. http://dx.doi.org/10.1785/bssa0790010141.
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Abstract A new procedure is described for estimating network-averaged P-wave spectra from short-period, teleseismic recordings of explosions. This procedure is then applied to a large sample of approximately 1000 digitized Nevada Test Site (NTS) explosion seismograms to simultaneously derive estimates of frequency-dependent station correction factors and network-averaged P-wave spectra for each of the 50 selected explosions. An analysis of the station correction factors is then presented which demonstrates that the Veith-Clawson (1972) B(Δ) curve for time domain mb adequately describes the teleseismic distance dependence of the spectral amplitude data over the entire short-period band extending from 0.50 to 2.25 Hz. A simplified scaling analysis of the network-averaged spectra is described and used to confirm the fact that the P-wave source coupling characteristics below the water table at the Yucca Flat and Pahute Mesa testing areas of NTS are essentially identical. We conclude that this new spectral measure can provide robust means for comparing different explosion testing areas.
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Walck, Marianne C. "Spectral estimates of teleseismic P-wave attenuation to 15 Hz." Bulletin of the Seismological Society of America 78, no. 2 (April 1, 1988): 726–40. http://dx.doi.org/10.1785/bssa0780020726.
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Abstract NORESS recordings of nuclear explosions in central Asia (Δ = 38°) provide new spectral attenuation estimates for frequencies from about 3 to 15 Hz. Two path spectra, representing propagation losses from the Shagan River and Degelen test sites to southern Norway, are calculated using the double-averaging technique of Bache et al. (1985, 1986). Both paths exhibit less attenuation than previously documented for explosions recorded teleseismically at the UKAEA arrays over the 1- to 8-Hz frequency range. The Shagan and Degelen spectra have somewhat different decay rates, perhaps reflecting variations in average source properties. Since the NORESS data extend to higher frequencies than previously available for attenuation measurements, we compare the NORESS spectral data to published models derived from NORSAR data (1 to 8 Hz) for the same path. The Degelen-NORSAR model is compatible with the NORESS data to about 7 Hz, but from 7 to 15 Hz, it predicts higher spectral amplitudes than are observed Using a hybrid absorption band-constant t* formulation, new models are derived which fit both the Shagan River path spectrum (t0* = 0.6 sec, τm = 0.05 sec, (t1* = 0.07 sec) and the Degelen spectrum (t0* = 0.6 sec, τm = 0.05 sec, (t1* = 0.05 sec) from 3 to 15 Hz. The NORESS data support frequency-dependent t* in the 3- to 15-Hz frequency range. The results also demonstrate that extrapolation of attenuation models obtained from longer period data to shorter periods may not predict the correct spectral levels. Actual high-frequency measurements are needed in order to characterize attenuation behavior at high frequencies.
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Tavakoli, Sasan, Poorya Shaghaghi, Simone Mancini, Fabio De Luca, and Abbas Dashtimanesh. "Wake waves of a planing boat: An experimental model." Physics of Fluids 34, no. 3 (March 2022): 037104. http://dx.doi.org/10.1063/5.0084074.
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The wake waves generated by the steady movement of a planing hull are analyzed by means of towing tank tests. Two sets of waves, including divergent and transverse waves, are identified and then analyzed. The wave period of the divergent waves is seen to decrease by the increase in speed of the vessel. These waves are seen to damp temporally. The mechanisms that lead to damping of the divergent wave were found to depend on the wave orbital Reynolds number in semi-planing regime, though that of in-planing regime is a function of the Reynolds number of the boat. The wake angle is seen to decrease with the increase in Froude number, the rate of which becomes relatively large in-planing regime. Transverse waves are captured through measurements, and it is shown that while their period is longer than those of the divergent waves, they are not noticeably damped. Throughout the spectral analysis, it is demonstrated that divergent waves reach a higher level of nonlinearity by the increase in Froude number and, hence, the wave energy is distributed over a boarder range of frequency. The height of the transverse wave is observed to become lower by the increase in speed, but as the towing speed increases, the probability density function curves of surface elevation deviate more and more from the Gaussian distribution.
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Hanson, Jeffrey L., Barbara A. Tracy, Hendrik L. Tolman, and R. Douglas Scott. "Pacific Hindcast Performance of Three Numerical Wave Models." Journal of Atmospheric and Oceanic Technology 26, no. 8 (August 1, 2009): 1614–33. http://dx.doi.org/10.1175/2009jtecho650.1.
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Abstract Although mean or integral properties of wave spectra are typically used to evaluate numerical wave model performance, one must look into the spectral details to identify sources of model deficiencies. This creates a significant problem, as basin-scale wave models can generate millions of independent spectral values. To facilitate selection of a wave modeling technology for producing a multidecade Pacific hindcast, a new approach was developed to reduce the spectral content contained in detailed wave hindcasts to a convenient set of performance indicators. The method employs efficient image processing tools to extract windsea and swell wave components from monthly series of nondirectional and directional wave spectra. Using buoy observations as ground truth, both temporal correlation (TC) and quantile–quantile (QQ) statistical analyses are used to quantify hindcast skill in reproducing measured wave component height, period, and direction attributes. An integrated performance analysis synthesizes the TC and QQ results into a robust assessment of prediction skill and yields distinctive diagnostics on model inputs and source term behavior. The method is applied to a set of Pacific basin hindcasts computed using the WAM, WAVEWATCH III, and WAVAD numerical wave models. The results provide a unique assessment of model performance and have guided the selection of WAVEWATCH III for use in Pacific hindcast production runs for the U.S. Army Corps of Engineers Wave Information Studies Program.
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Boore, David M. "Basin waves on a seafloor recording of the 1990 Upland, California, earthquake: Implications for ground motions from a larger earthquake." Bulletin of the Seismological Society of America 89, no. 1 (February 1, 1999): 317–24. http://dx.doi.org/10.1785/bssa0890010317.
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AbstractThe velocity and displacement time series from a recording on the seafloor at 74 km from the 1990 Upland earthquake (M = 5.6) are dominated by late-arriving waves with periods of 6 to 7 sec. These waves are probably surface waves traveling across the Los Angeles basin. Response spectra for the recording are in agreement with predictions from empirical regression equations and theoretical models for periods less than about 1 sec but are significantly larger than those predictions for longer periods. The longer-period spectral amplitudes are controlled by the late-arriving waves, which are not included in the theoretical models and are underrepresented in the data used in the empirical analyses. When the motions are scaled to larger magnitude, the results are in general agreement with simulations of wave propagation in the Los Angeles basin by Graves (1998).
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Pascolo, Sara, Marco Petti, and Silvia Bosa. "On the Wave Bottom Shear Stress in Shallow Depths: The Role of Wave Period and Bed Roughness." Water 10, no. 10 (September 28, 2018): 1348. http://dx.doi.org/10.3390/w10101348.
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Lagoons and coastal semi-enclosed basins morphologically evolve depending on local waves, currents, and tidal conditions. In very shallow water depths, typical of tidal flats and mudflats, the bed shear stress due to the wind waves is a key factor governing sediment resuspension. A current line of research focuses on the distribution of wave shear stress with depth, this being a very important aspect related to the dynamic equilibrium of transitional areas. In this work a relevant contribution to this study is provided, by means of the comparison between experimental growth curves which predict the finite depth wave characteristics and the numerical results obtained by means a spectral model. In particular, the dominant role of the bottom friction dissipation is underlined, especially in the presence of irregular and heterogeneous sea beds. The effects of this energy loss on the wave field is investigated, highlighting that both the variability of the wave period and the relative bottom roughness can change the bed shear stress trend substantially.
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Magnusson, Anne Karin, Robert Jensen, and Val Swail. "Spectral shapes and parameters from three different wave sensors." Ocean Dynamics 71, no. 9 (July 15, 2021): 893–909. http://dx.doi.org/10.1007/s10236-021-01468-7.
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AbstractThe quality of wave measurements is of primary importance for the validation of wave forecasting models, satellite wave calibration and validation, wave physics, offshore operations and design and climate monitoring. Validation of global wave forecasts revealed significant regional differences, which were linked to the different wave buoy systems used by different countries. To fully understand the differences between the wave measurement systems, it is necessary to go beyond investigations of the integral wave parameters height, period and direction, into the frequency spectra and the four directional Fourier parameters that are used to estimate the directional distribution. We here analyse wave data measured from three different sensors (non-directional Datawell Waverider buoy, WaveRadar Rex, Optech laser) operating at the Ekofisk oil production platform located in the central North Sea over a period of several months, with significant wave height ranging from 1 to 10 m. In general, all three sensors provide similar measurements of the integral wave properties and frequency spectra, although there are some significant differences which could impact design and operations, forecast verification and climate monitoring. For example, the radar underestimates energy in frequency bands higher than 8 s by 3–5%, swell (12.5–16 s) by 5–13%, while the laser has 1–2% more energy than the Waverider in the most energetic bands. Lee effects of structures are also estimated. Lower energy at the frequency tail with the radar has an effect on wave periods (they are higher); wave steepness is seen to be reduced by 10% in the wind seas. Goda peakedness and the unidirectional Benjamin-Feir index are also examined for the three sensors.
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YASUDA, Tomohiro, Yuta MORIKAWA, and Hajime MASE. "A STUDY ON ESTIMATION METHOD OF SIGNIFICANT WAVE PERIOD AND SIGNIFICANT WAVE HEIGHT OF DOUBLE-PEAKED SPECTRAL WAVES." Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 76, no. 2 (2020): I_187—I_192. http://dx.doi.org/10.2208/kaigan.76.2_i_187.
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Mooneyham, Jonny, Sean C. Crosby, Nirnimesh Kumar, and Brian Hutchinson. "SWRL Net: A Spectral, Residual Deep Learning Model for Improving Short-Term Wave Forecasts." Weather and Forecasting 35, no. 6 (December 2020): 2445–60. http://dx.doi.org/10.1175/waf-d-19-0254.1.
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AbstractSkillful nearshore wave forecasts are critical for providing timely alerts of hazardous wave events that impact navigation or recreational beach use. While typical forecasts provide bulk wave parameters (wave height and period), spectral details are needed to correctly predict wave and associated circulation dynamics in the nearshore region. Currently, global wave models, such as WAVEWATCH III (WW3), make spectral predictions, but do not assimilate regional buoy observations. Here, Spectral Wave Residual Learning Network (SWRL Net), a fully convolutional neural network, is trained to take recent WW3 forecasts and buoy observations, and produce corrections to frequency-directional WW3 spectra, transformed into directional buoy moments, for up to 24 h in the future. SWRL Net is trained with 10 years of collocated NOAA’s WW3 CFSR reanalysis predictions and buoy observations at three locations offshore of the U.S. western coast. At buoy locations SWRL Net residual corrections result in wave height root-mean-square error (RMSE) reductions of 23%–50% in the first 6 h and 10%–20% thereafter. Sea frequencies (5–10 s) show the most improvement compared to swell (12–20 s). SWRL Net reduces mean direction RMSE by 28%–54% and mean period RMSE by 20%–56% over 24 forecast hours. While each model is trained and tested at independent locations, SWRL Net exhibits generalization when introduced to data from other locations, suggesting future development may be composed of training sets from multiple locations.
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Chaichitehrani, Nazanin, Mohammad Nabi Allahdadi, and Chunyan Li. "Simulation of Low Energy Waves during Fair-Weather Summer Conditions in the Northern Gulf of Mexico: Effect of Whitecapping Dissipation and the Forcing Accuracy." Atmosphere 13, no. 12 (December 7, 2022): 2047. http://dx.doi.org/10.3390/atmos13122047.
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Simulating WAves Nearshore (SWAN) on a structured grid over the Louisiana shelf in the northern Gulf of Mexico is used to evaluate the performance of three different classes of formulations for quantifying wind input and whitecapping dissipation. The formulations include Komen based on the mean spectral parameters, Westhuysen based on the saturation concept of the wave groups, and the most recent observation-based physics package ST6. The evaluation was implemented for two summer months (July and August 2015) to assess these formulations for a low wave energy period. The modeling area consists of the Louisiana inner shelf with the offshore open boundary located beyond the continental shelf. The model was forced using the spatially variable Climate Forecast System Reanalysis (CFSR) wind field and wave parameters obtained from the NOAA’s WAVEWATCH-III (WWIII) model along the open boundaries. Simulated wave parameters and spectra regarding each formulation were evaluated and compared with measured wave data at NDBC stations; comparisons showed that the most appropriate formulation for the simulation of low energy waves for the study area to be ST6. The e performance of each whitecapping formulation was described by examining 1D/2D spectra and the source term balance at different met-ocean conditions during the simulation period. It was also shown that the inaccuracies in the input wind field and boundary conditions can substantially contribute to the model inaccuracy.
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Satyavathi, Pentapati, Makarand C. Deo, Jyoti Kerkar, and Ponnumony Vethamony. "Reevaluation of Design Waves Off the Western Indian Coast Considering Climate Change." Marine Technology Society Journal 50, no. 1 (January 1, 2016): 88–98. http://dx.doi.org/10.4031/mtsj.50.1.6.
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AbstractKnowledge of design waves with long return periods forms an essential input to many engineering applications, including structural design and analysis. Such extreme or long-term waves are conventionally evaluated using observed or hindcast historical wave data. Globally, waves are expected to undergo future changes in magnitude and behavior as a result of climate change induced by global warming. Considering future climate change, this study attempts to reevaluate significant wave height (Hs) as well as average spectral wave period (Tz) with a return period of 100 years for a series of locations along the western Indian coastline. Historical waves are simulated using a numerical wave model forced by wind data extracted from the archives of the National Center for Environmental Prediction and the National Center for Atmospheric Research, while future wave data are generated by a state-of-the-art Canadian general circulation model. A statistical extreme value analysis of past and projected wave data carried out with the help of the generalized Pareto distribution showed an increase in 100-year Hs and Tz along the Indian coastline, pointing out the necessity to reconsider the safety of offshore structures in the light of global warming.
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Cao, Yuhan, Chunyan Li, and Changming Dong. "Atmospheric Cold Front-Generated Waves in the Coastal Louisiana." Journal of Marine Science and Engineering 8, no. 11 (November 11, 2020): 900. http://dx.doi.org/10.3390/jmse8110900.
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Atmospheric cold front-generated waves play an important role in the air–sea interaction and coastal water and sediment transports. In-situ observations from two offshore stations are used to investigate variations of directional waves in the coastal Louisiana. Hourly time series of significant wave height and peak wave period are examined for data from 2004, except for the summer time between May and August, when cold fronts are infrequent and weak. The intra-seasonal scale variations in the wavefield are significantly affected by the atmospheric cold frontal events. The wave fields and directional wave spectra induced by four selected cold front passages over the coastal Louisiana are discussed. It is found that significant wave height generated by cold fronts coming from the west change more quickly than that by other passing cold fronts. The peak wave direction rotates clockwise during the cold front events. The variability of the directional wave spectrum shows that the largest spectral density is distributed at low frequency in the postfrontal phase associated with migrating cyclones (MC storms) and arctic surges (AS storms).
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Allahdadi, Mohammad Nabi, Ruoying He, and Vincent S. Neary. "Predicting ocean waves along the US east coast during energetic winter storms: sensitivity to whitecapping parameterizations." Ocean Science 15, no. 3 (June 6, 2019): 691–715. http://dx.doi.org/10.5194/os-15-691-2019.
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Abstract. The performance of two methods for quantifying whitecapping dissipation incorporated in the Simulating Waves Nearshore (SWAN) wave model is evaluated for waves generated along and off the US east coast under energetic winter storms with a predominantly westerly wind. Parameterizing the whitecapping effect can be done using the Komen-type schemes, which are based on mean spectral parameters, or the saturation-based (SB) approach of van der Westhuysen (2007), which is based on local wave parameters and the saturation level concept of the wave spectrum (we use “Komen” and “Westhuysen” to denote these two approaches). Observations of wave parameters and frequency spectra at four National Data Buoy Center (NDBC) buoys are used to evaluate simulation results. Model–data comparisons show that when using the default parameters in SWAN, both Komen and Westhuysen methods underestimate wave height. Simulations of mean wave period using the Komen method agree with observations, but those using the Westhuysen method are substantially lower. Examination of source terms shows that the Westhuysen method underestimates the total energy transferred into the wave action equations, especially in the lower frequency bands that contain higher spectral energy. Several causes for this underestimation are identified. The primary reason is the difference between the wave growth conditions along the east coast during winter storms and the conditions used for the original whitecapping formula calibration. In addition, some deficiencies in simulation results are caused along the coast by the “slanting fetch” effect that adds low-frequency components to the 2-D wave spectra. These components cannot be simulated partly or entirely by available source terms (wind input, whitecapping, and quadruplet) in models and their interaction. Further, the effect of boundary layer instability that is not considered in the Komen and Westhuysen whitecapping wind input formulas may cause additional underestimation.
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Gemmrich, Johannes, and Chris Garrett. "Unexpected Waves." Journal of Physical Oceanography 38, no. 10 (October 1, 2008): 2330–36. http://dx.doi.org/10.1175/2008jpo3960.1.
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Abstract Extreme, or “rogue,” waves are those in the tail of the probability distribution and are a matter of great concern and considerable research. They may be partly associated with non-Gaussian behavior caused by resonant nonlinear interactions. Here it is shown that even in a Gaussian sea, “unexpected” waves, in the sense of, for example, waves twice as large as any in the preceding 30 periods, occur with sufficient frequency to be of interest and importance. The return period of unexpected waves is quantified as a function of the height multiplier and prior quiescent interval for various spectral shapes, and it is shown how the return period is modified if allowance is made for nonlinear changes in wave shape and/or a buildup of one or more waves prior to the unexpected wave. The return period of “two-sided” unexpected waves, with subsequent as well as prior quiescence, is also evaluated.
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Saprykina, Yana, and Olga Kuznetsova. "INFLUENCE OF WAVE TRANSFORMATION PROCESSES ON EVOLUTION OF UNDERWATER BEACH PROFILE." Coastal Engineering Proceedings, no. 36 (December 30, 2018): 65. http://dx.doi.org/10.9753/icce.v36.papers.65.
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On the base of field experimental data were confirmed that the main wave parameters for cross-shore sediment transport are the significant wave height, spectral peak period and wave steepness. Waves with narrowband spectrum more effect on changes of underwater profile. For a qualitative assessment of erosion/accumulation the Dean parameter, the Ursell and Iribarren numbers can be used. However the physical processes of wave transformation play an important role. The most significant are nonlinear wave transformation and wave breaking, especially the type of wave breaking.
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Medina Rodríguez, Ayrton Alfonso, Gregorio Posada Vanegas, Rodolfo Silva Casarín, Edgar Gerardo Mendoza Baldwin, Beatriz Edith Vega Serratos, Felipe Ernesto Puc Cutz, and Enrique Alejandro Mangas Che. "Experimental Investigation of the Hydrodynamic Performance of Land-Fixed Nearshore and Onshore Oscillating Water Column Systems with a Thick Front Wall." Energies 15, no. 7 (March 24, 2022): 2364. http://dx.doi.org/10.3390/en15072364.
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Most experimental research on land-fixed Oscillating Water Column (OWC) systems assume that the OWC-water wave interaction happens with waves that propagate normally towards the device. However, the angle of incidence of the waves can determine the performance of the OWC, in particular the wave period at which the device resonates. In this study, an experimental investigation to examine the interaction of regular, oblique, water waves with a land-fixed, thick-front wall OWC device in terms of its hydrodynamic performance is reported. A 1:20 Froude scale was used to replicate a single chamber of the Mutriku Wave Energy Plant (MWEP), and a series of tests were carried out in a spectral wave basin. The goal of this study is to look at how incident wave direction and device location affect the hydrodynamic performance of land-fixed OWC systems in regular wave conditions with varying wave heights. The hydraulic performance includes the assessment of the wave amplification factor, hydrodynamic efficiency, the non-dimensional air pressure inside the chamber and non-dimensional water pressures on the chamber walls. The findings show that, for the nearshore OWC device, the period at which resonance occurs decreases when the incident wave angle increases. For the corresponding wave angles, similar results were found for the onshore and nearshore OWC devices, with a slight frequency shift in the bandwidth of the hydrodynamic efficiency. Furthermore, it was found that when wave height increases, the hydrodynamic efficiency improves for both short and long wave periods, with the exception of the resonance period, where the trend is reversed. Finally, regardless of the location, an OWC device with a thick front wall performs well when interacting with intermediate and long-period waves.
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Malinga, S. B., and J. M. Ruohoniemi. "The quasi-two-day wave studied using the Northern Hemisphere SuperDARN HF radars." Annales Geophysicae 25, no. 8 (August 29, 2007): 1767–78. http://dx.doi.org/10.5194/angeo-25-1767-2007.
Full textAbstract:
Abstract. Data from the Super Dual Radar Network (SuperDARN) radars for 2002 were used to study the behaviour of the quasi-two-day wave (QTDW) in the Northern Hemisphere auroral zone. The period of the QTDW is observed to vary in the range of ~42–56 h, with the most dominant period being ~48 h and secondary peaks at ~42- and ~52-h. The spectral power shows a seasonal variation with a peak power (max~70) in summer. The power shows variations of several days and there is also evidence of changes in wave strength with longitude. The 42-h and the 48-h components tend to be strongly correlated in summer. The onset of enhanced wave activity tends to coincide with the westward acceleration of the zonal mean flow and occurs at a time of strong southward meridional flow. The most frequent instantaneous hourly period is in the 40 to 50 h period band, in line with the simultaneous dominance of the 42-h and the 48-h components. The wave numbers are less variable and are around −2 to −4 during times of strong wave activity. For a period of ~48 h, the zonal wave number is about −3 to −4, using a negative value to indicate westward propagating waves. The 42-h and the 52-h components cover a wider band in the −4 to 1 range. The wide zonal wave number spectrum in our results may account for the observed longitudinal variation in the spectral power of the wave.
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Yaitskaya, Natalia. "The Wave Climate of the Sea of Azov." Water 14, no. 4 (February 12, 2022): 555. http://dx.doi.org/10.3390/w14040555.
Full textAbstract:
This article describes the results of the retrospective numerical simulation of wind waves in the Sea of Azov using the SWAN spectral wave model and the ERA-Interim global reanalysis for 1979–2019. A digital model of the sea-floor relief of the Sea of Azov was used for the calculations. This model was built using a bathymetric map of the Sea of Azov, as well as nautical charts and remote sensing data. Verification of the model for the conditions that characterize the Sea of Azov was conducted using data from ship observations of wind waves. The features of the mean long-term wind wave patterns, as well as the seasonal, interannual, and interdecadal dynamics were presented. The main focus was on the following parameters: significant wave height, wave period, and wave direction. A description of storm conditions and a comparison with surge phenomena and ice conditions was also completed. The results indicated that, in contrast to Taganrog Bay, the wave patterns were heavily influenced according to the time of year (i.e., the seasons). The maximum wave heights were typical for the cold season of the year but not for the ice-free period. The interannual dynamics of wind waves were characterized by the alternation of three five-year periods of strengthening and weakening of wind waves. After 2002, the wave height increased in the summer and autumn seasons and slightly decreased in winter and spring. A shift of the storm season to a warmer period was also detected.
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Laštovička, J., P. Križan, P. Šauli, and D. Novotná. "Persistence of the planetary wave type oscillations in <i>fo</i>F2 over Europe." Annales Geophysicae 21, no. 7 (July 31, 2003): 1543–52. http://dx.doi.org/10.5194/angeo-21-1543-2003.
Full textAbstract:
Abstract. Planetary waves are oscillations of very predominantly tropospheric origin with typical periods of about 2–30 days. Their dominant zonal wave numbers are 1, 2 and 3, i.e. the waves are of large-scale (global) character. The planetary wave type oscillations have been observed in the lower and middle atmosphere but also in the ionosphere, including the ionospheric F2-layer. Here, we deal only with the oscillations analyzed for four European stations over a solar cycle with the use of the Meyer and Morlet wavelet transforms. Waves with periods near 5, 10 and 16 days are studied. Only events with a duration of three wave-cycles and more are considered. The 5-day period wave events display a typical duration of 4 cycles, while 10- and 16-day wave events are less persistent, with a typical duration of about 3.5 cycles and 3 cycles, respectively. The persistence pattern in terms of number of cycles and in terms of number of days is different. In terms of number of cycles, the typical persistence of oscillations decreases with increasing period. On the other hand, in terms of number of days the typical persistence evidently increases with increasing period. The spectral distribution of event duration is too broad to allow for a reasonable prediction of event duration. Thus, the predictability of the planetary wave type oscillations in foF2 seems to be very questionable.Key words. Ionosphere (ionosphere-atmosphere interaction, mid-latitude ionosphere, ionospheric disturbances) – Meteorology and atmospheric dynamics (waves and tides)
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Chael, Eric P. "Spectral scaling of earthquakes in the Miramichi region of New Brunswick." Bulletin of the Seismological Society of America 77, no. 2 (April 1, 1987): 347–65. http://dx.doi.org/10.1785/bssa0770020347.
Full textAbstract:
Abstract Seismograms of 12 earthquakes in the Miramichi region of New Brunswick were analyzed to determine source scaling relations. The events ranged in magnitude from 3.3 to 5.8 (mbLg). P-wave spectra between 1 and 20 Hz were calculated using digital records from station RSNY (Δ = 6°). Spectral ratios were then formed using the main shock as a reference event. Because the travel paths were virtually identical for all of the signals, the spectral ratios yield the scaling of the sources as a function of frequency. The spectral ratio curves show a smooth progression with event size, with their separation decreasing toward higher frequencies. These data were compared with theoretical curves for source models whose displacement spectra roll off as ω−2 and ω−3 above the corner frequencies. The data strongly favor the ω−2 models; the ω−3 models predict greater variation across the 1- to 20-Hz band than is observed. Comparison of the P-wave scaling at 15 Hz with the Rayleigh wave scaling at a period of 8 sec indicates that stress drop may increase with moment for these events, although not as fast as Nuttli (1983) has suggested for intraplate earthquakes.