Journal articles on the topic 'Nakamura Spectra'
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Asai, K., T. Dotani, K. Mitsuda, H. Inoue, Y. Tanaka, and W. H. G. Lewin. "Energy Spectra of X 1636-536 Observed with ASCA." Symposium - International Astronomical Union 188 (1998): 354–55. http://dx.doi.org/10.1017/s0074180900115505.
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Absorption line features were detected at 4.1 keV from X 1636-536 with the Tenma satellite in the spectra of X-ray bursts (Waki et al., 1984). Similar features were also detected from X 1608-52 and EXO 1747-214 during bursts (Nakamura et al., 1988; Magnier et al., 1989). These features at 4.1 keV may be interpreted as the redshifted Kα absorption line of helium-like iron atoms. However, such interpretation requires extremely soft equation of state for the nuclear matter, and confirmation with high resolution detectors is urged (Lewin et al., 1993). To investigate the line features, we observed X 1636-536 with ASCA for ~ 240 ksec.
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Sinadinovski, Cvetan, Snježana Markušić, Davor Stanko, Kevin F. McCue, and Lazo Pekevski. "Seismic Analysis of Moderate Size Earthquakes Recorded on Stations at Close Epicentral Distances." Applied Sciences 12, no. 1 (January 4, 2022): 470. http://dx.doi.org/10.3390/app12010470.
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In this study, we analyzed the near-field seismic records of two moderate sized earthquakes in the Western Balkan region: the September 2016 Skopje earthquake, magnitude ML5.3 and the March 2020 Zagreb earthquake, magnitude ML5.5. Such recordings at close epicentral distances are rare and are thus very useful for testing some of the theoretical assumptions used in modeling earthquake risk. Firstly, response spectra were computed using the digital time histories for the three closest stations to the Skopje 2016 earthquake and the two closest stations to the Zagreb 2020 earthquake. Their characteristics were examined in terms of frequency and peak amplitude ranges. Secondly, the Nakamura method was applied to the records from the selected five stations coded SKO, FCE, IZIIS, QUHS, and QARH. The results of the spectral analysis were compared with interpretations from the geological and geotechnical maps at each location. Our findings support the idea that these combined methods can be used to categorize the underlying structural profile to a first approximation and can be used to derive velocity models.
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Kitamura, Masatoshi, and Yasuhisa Nakamura. "Empirical Determination of the Gravity-Darkening Exponent for the Secondary Components Filling the Roche Lobe in Semi-Detached Close Binary Systems." International Astronomical Union Colloquium 108 (1988): 217–18. http://dx.doi.org/10.1017/s0252921100093866.
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The ordinary semi-detached close binary system consists of a main-sequence primary and subgiant (or giant) secondary component where the latter fills the Roche lobe. From a quantitative analysis of the observed ellipticity effect, Kitamura and Nakamura (1986) have deduced empirical values of the exponent of gravity-darkening for distorted main-sequence stars in detached systems and found that the empirical values of the exponent for these stars with early-type spectra are close to the unity, indicating that the subsurface layers of early-main sequence stars in close binaries are actually in radiative equilibrium. The exponent of gravity-darkening can be defined by H ∝ gα with H as the bolonetric surface brightness and g as the local gravity on the stellar surface.
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Feldzensztajn, Mateusz, and Adam Mazikowski. "Comparison of modelling and measurement results of spectra emitted by a programmable lamp." Photonics Letters of Poland 10, no. 2 (June 30, 2018): 42. http://dx.doi.org/10.4302/plp.v10i2.826.
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Nowadays artificial light with optimized spectrum is used in many different applications. For instance, it is widely used in museums and exhibitions to illuminate the art. Moreover, such light stimulates the growth of plants, or can be applied in industry and healthcare. To achieve the best results for each application, adjusting of dedicated spectrum is required, that is a complicated task. The ongoing research is focused on simplifying this process. In this paper we present the developed lamp with programmable spectrum, and its user interface. Predicted and measured output spectra are investigated. Full Text: PDF ReferencesMottier, P., LEDs for Lighting Applications, Willey (2009) CrossRef Pimputkar, S., Speck, J.S., DenBaars, S.P., Nakamura, S., "Prospects for LED lighting", Nature photonics 3 (4), 180 (2009) CrossRef Knulst, A. J., Mooijweer, R., Jansen, F. W., Stassen, L. P., and Dankelman, J., "Indicating shortcomings in surgical lighting systems," Minim. Invasive Ther. Allied Technol. 20 (5), 267–275 (2011) CrossRef Blaszczak, U., Gryko, L., Palkowska, A., Kulesza, E., Zajac, A., "Color mixing in LED illuminating system for endoscopic purposes", Lighting Conference of the Visegrad Countries (Lumen), IEEE (17 November 2016) CrossRef Nanya, K., Ishigami, Y., Hikosaka, S., Goto, E., "Effects of blue and red light on stem elongation and flowering of tomato seedlings", Acta Hortic. 956, pp. 264–266 (2012). CrossRef Cegielski, T. , Bujalski, D. , Kowalczyk, K. , Gajc-Wolska, J. , Hemka, L., "Use of light emission programming in tomato grow light system", Proceedings of Electrotechnical Institute 63 (273), 79-94 (2016) CrossRef Mazikowski, A., Feldzensztajn, M., "Lamp of adjustable spectrum for photographic usage", Proc. SPIE 10445, Photonics Applications in Astronomy, Communications, Industry, and High Energy Physics Experiments, 104450K (2017) CrossRef CREE Inc, Cree® XLamp® XT-E LEDs Product family data sheet (accessed 16 April 2018). DirectLink Dyble, M., Narendran, N., Bierman, A., Klein, T., "Impact of dimming white LEDs: chromaticity shifts due to different dimming methods", Optics and Photonics 2005, San Diego, California, United States DirectLink
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Mendonça, Christovam, and Said R. Rabbani. "Anharmonic Librations and the Temperature Dependence of NQR Frequencies." Zeitschrift für Naturforschung A 51, no. 5-6 (June 1, 1996): 698–704. http://dx.doi.org/10.1515/zna-1996-5-655.
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Abstract The temperature dependence of NQR frequencies of nuclei in molecules undergoing quasi-har-monic rotational oscillations is calculated. Following the model proposed by Bayer, the instanta-neous orientation of the electric field gradient principal axes is assumed to change from its average orientation as a result of rotational oscillations, while the EFG magnitude remains constant. The eigenstates and energy eigenvalues of a rotator in a potential of the form V(θ)= V2θ2 - K4θ4 are calculated by standard perturbation methods, followed by the evaluation of statistical averages of square angular amplitudes. For molecular crystals with more than one molecule in a unit cell the angular displacements are expressed in terms of normal coordinates, and the same procedure is followed. The final expression for the change in the NQR frequency consists of two terms, the first one being related to the harmonic part of the potential and the second one to the quartic term. At the absolute zero it yields a nonzero contribution to ⟨θ2⟩, and for high temperatures it reproduces the nonlinear character of νQ(T) observed experimentally. The model has been tested with measure-ments on solid Cl2 performed by Nakamura and Chihara, combined with libration mode frequencies measured in Raman spectroscopy by Cahill and Leroi and analysed according to our anharmonic libration picture. The fitting of our equation to experimental data supports Cahill and Leroi's hypothesis about the existence of an undetected libration mode in Cl2 Raman spectra of frequency near 60 cm- 1
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Lermo, Javier, and Francisco J. Chávez-García. "Site effect evaluation using spectral ratios with only one station." Bulletin of the Seismological Society of America 83, no. 5 (October 1, 1993): 1574–94. http://dx.doi.org/10.1785/bssa0830051574.
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Abstract The spectral ratio technique is a common useful way to estimate empirical transfer function to evaluates site effects in regions of moderate to high seismicity. The purpose of this paper is to show that it is possible to estimate empirical transfer function using spectral ratios between horizontal and vertical components of motion without a reference station. The technique, originally proposed by Nakamura to analyze Rayleigh waves in the microtremor records, is presented briefly and it is discussed why it may be applicable to study the intense S-wave part in earthquake records. Results are presented for three different cities in Mexico: Oaxaca, Oax., Acapulco, Gro., and Mexico City. These cities are very different by their geological and tectonic contexts and also by the very different epicentral distances to the main seismogenic zones affecting each city. Each time we compare the results of Nakamura's technique with standard spectral ratios. In all three cases the results are very encouraging. We conclude that, if site effects are caused by simple geology, a first estimate of dominant period and local amplification level can be obtained using records of only one station.
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Watanabe, Hikari, Yuya Tabata, Jihae Han, Isao Shitanda, Yasuhiro Umebayashi, and Masayuki Itagaki. "Development of New Borate-Based Lithium Ionic Liquid for Next Generation Lithium-Ion Battery." ECS Meeting Abstracts MA2022-02, no. 3 (October 9, 2022): 200. http://dx.doi.org/10.1149/ma2022-023200mtgabs.
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Solvate ionic liquids (SILs), which consist of a solvate ion and its counter ion, are expected as the electrolyte for the new generation Lithium-ion batteries [1]. Li-glymes SIL is an equimolar mixture of lithium salts and glyme of an oligoether such as triglyme and tetraglyme (Gn: CH3O-(CH2CH2O) n -CH3, n = 3 and 4). Li-glymes SIL shows favorable liquid properties like ordinary aprotic ionic liquids; negligible vapor pressure, practically non-inflammability, ionic conductivity and electrochemical stability, and so on. Watanabe et al. [2] have proposed that the specific Li+ ion hopping conduction occurs in the Li-glymes SIL. In Lithium-ion batteries with Li-glymes SIL, the desolvated Li+ ions are intercalated into graphite electrode, however, the co-intercalation of Li+ ion and glyme into the electrode occurs in the battery using the excess glyme electrolyte solution [3]. This suggests that the solvent activity affects the electrode reaction. In the present study, we prepared lithium ionic liquids with oligoether chains (Figure 1) and measured those physical and electrochemical properties. Infrared spectroscopic (IR) measurements were carried out to identify the prepared lithium ionic liquids. An intense peak, which cannot be observed in the IR spectra of the raw materials, appears in approximately 1000 cm-1. This peak is attributable to B-O vibration mode, suggesting that the lithium ionic liquids are synthesized. We here define the new lithium ionic liquids as LiB(Gn)4 (n = 3 or 4). The ionic conductivities of LiB(G3)4 and Li(B4)4 are 0.20 and 0.37 mS cm-1, respectively. In addition, Li+ ion transport number is approximately 0.5 for both LiB(G3)4 and Li(B4)4., which is higher than that of electrolyte solution used in a commercial lithium-ion battery. This suggests that Li+ ion hopping conduction may occur via the exchange among glymes which are side chain of anion. References [1] C. Austen Angell, Y. Ansari, Z. Zhao, Faraday Discuss., 154, 9-27 (2012). [2] K. Yoshida, M. Nakamura, Y. Kazue, N. Tachikawa, S. Tsuzuki, S. Seki, K. Dokko, M. Watanabe, J. Am. Chem. Soc., 133, 13121-13129 (2011). [3] H. Moon, R. Tatara, T. Mandai, K. Ueno, K. Yoshida, N. Tachikawa, T. Yasuda, K. Dokko, M. Watanabe, J. Phys. Chem. C, 118, 20246-20256 (2014). Figure 1
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Dravinski, M., G. Ding, and K. L. Wen. "Analysis of spectral ratios for estimating ground motion in deep basins." Bulletin of the Seismological Society of America 86, no. 3 (June 1, 1996): 646–54. http://dx.doi.org/10.1785/bssa0860030646.
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Abstract Use of Nakamura's spectral ratio (horizontal versus vertical components) is investigated theoretically for deep sedimentary basins by considering semi-circular and semi-spherical valleys. The ratio is evaluated from the steady-state surface response for different incident waves. Based on this ratio, both the resonant frequencies and ground motion amplification are determined. The results based on Nakamura's ratio are compared with those based on the sediment-to-bedrock spectral ratios (Kagami's ratio). The results show that for both two- and three-dimensional models, Nakamura's technique predicts well the fundamental resonant frequency, but it could not determine higher resonant frequencies of the basins. The error in Nakamura's estimate of the fundamental resonant frequency increases for stations near the valley center. For alluvial valleys considered in this article, Nakamura's ratio failed to predict accurately surface ground-motion amplification.
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Dian-Ping, Li, Dou Lin-Ming, Lu Cai-Ping, Cao An-Ye, and Hu Yin-Ru. "Nakamura Spectral Ratio Characteristics of Microseism Signal Induced by Relieve-Shot." Procedia Engineering 26 (2011): 1296–304. http://dx.doi.org/10.1016/j.proeng.2011.11.2304.
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Ozalp, Mustafa Kemal, and Serdar Beji. "TIME DOMAIN COMPARISONS OF MEASURED AND SPECTRALLY SIMULATED BREAKING WAVES." Coastal Engineering Proceedings, no. 35 (June 23, 2017): 12. http://dx.doi.org/10.9753/icce.v35.waves.12.
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For realistic wave simulations in the nearshore zone besides nonlinear interactions, the dissipative effects of wave breaking must also be taken into account. This paper presents the applications of a spectral nonlinear wave model with a dissipative breaking mechanism introduced by Beji and Nadaoka (1997). Results obtained for spectral components are converted to the time series and compared with Beji and Battjes' (1993) laboratory measurements and the field measurements of Nakamura and Katoh (1992) in the surf zone. While the model predicts the spilling-type breaking of irregular waves in acceptable agreement with the measurements in time domain, the agreement is unsatisfactory for plunging-type breakers.
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Molnar, Sheri, and John F. Cassidy. "A Comparison of Site Response Techniques Using Weak-Motion Earthquakes and Microtremors." Earthquake Spectra 22, no. 1 (February 2006): 169–88. http://dx.doi.org/10.1193/1.2160525.
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The applicability of the microtremor spectral ratio method is examined by comparing microtremor and weak-motion earthquake site responses at seven permanent strong-motion sites in Victoria, British Columbia. For each site, a weak-motion earthquake standard spectral ratio (bedrock reference), the average horizontal-to-vertical spectral ratio of up to five weak-motion earthquakes, and the average microtremor (Nakamura method) spectral ratio are compared. The geologic setting of Victoria is ideal for site response studies with a near-surface high impedance contrast between thin geologic layers of Victoria clay (about 11 m maximum in this study) and Pleistocene till or bedrock. Regardless of excitation source (weak-motion earthquakes or microtremors) and spectral ratio method, similar peak amplitudes and fundamental frequencies were found. Thicker material (>10 m) sites displayed higher peak amplitudes (up to six times amplification) at frequencies of 2–5 Hz compared to sites with a thin lens of material (<3 m) over bedrock that showed peak amplitudes at frequencies of >8 Hz.
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Dubos, Noalwenn, Annie Souriau, Christian Ponsolles, Jean-François Fels, and Guy Sénéchal. "Sites response estimates at the city of Lourdes, Pyrenees, France, using the spectral ratio method." Bulletin de la Société Géologique de France 174, no. 1 (January 1, 2003): 33–44. http://dx.doi.org/10.2113/174.1.33.
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Abstract The city of Lourdes, in the central part of the French Pyrenees, has been damaged several times by earthquakes, in particular in 1660 and 1750, two events which partly destroyed the city [Lambert et Levret-Albaret, 1996]. The Pyrenees is the most seismically active area in France. Historical seismicity indicates the possible occurrence of a magnitude 6 event in the Lourdes area. As Lourdes is an important place of pilgrimage with more than five millions of visitors each year, the evaluation of the seismic risk is of major importance. To this purpose, it is necessary first to correctly identify the active faults near the city, second to determine the ground motion response to local events, also called site effects. The active faults are rather well known thanks to the permanent network of the Observatoire Midi-Pyrénées [Souriau et Pauchet, 1998], and complementary studies [Dubos, 2000] (fig. 1). In the present paper, we present the results of an experiment devoted to the determination of the site effects in the city of Lourdes, using a classical spectral ratio method based on the record of small local events. Although the extrapolation from weak motion to strong motion is often non linear [Darragh et Shakal, 1991 ; Seekins et Boatwright, 1994], this approach gives crucial information for the evaluation of the ground response in case of a magnitude 6 event. The Pyrenees are an intraplate collision range [Choukroune, 1992]. A major tectonic feature is the North Pyre-nean Fault (FNP, fig. 1), which separates the Paleozoic Axial Zone to the south from the North Pyrenean Zone, made of Mesozoic sediments, to the north. Lourdes is located inside this latter unit (fig. 1). Quaternary glaciations have added various superficial structures [Alimen, 1964]. The city, at an altitude of about 400 m, is at the junction of five glacial beds (fig. 2), two of them corresponding to the Gave de Pau river. Two heights, the Beout (719 m) and the Pic du Jer (1948 m), are located south of the city. The experiment has been conducted during seven months using ten digital three-component instruments with broadband sensors. They have been set up with interstation spacing of 200 m to 1200 m. The station locations (fig. 2 and table I) were chosen by taking into account the importance of some sites for the population, but also the geological nature of the ground. It is well known that site effects are strongly influenced by the lithological features of the superficial structures, which may induce resonance phenomena, and by the topography of the surface and layer interfaces, which may induce focusing effects [Gao et al., 1996]. In our experiment, all the stations are at about the same altitude (400 m ± 40 m), except CIT located on the slope of the Beout at an altitude of 535 m. ROC, CIT, HOP and CHA are on the bedrock, EDF is at the foot of an ophite cliff. CHA is located half-way up the 40 meter-heigh hill of the castle. The other stations are on the sediments. GEN and PMP are at the base of buildings of 5 levels and 7 levels respectively, these structures may possibly modify the site effects [Wirgin and Bard, 1996]. 19 local events with magnitude 1.4 to 3.2 at epicentral distance 5 to 62 km have been analysed (fig. 3), as well as two regional events (table II). The local events are well representative of the local seismicity, they have been recorded at many stations (table II) with a very good signal to noise ratio. As shown by Riepl et al. [1998], eight to ten events per station are sufficient to define correctly the site effects. Only GEN does not fulfil this criterion because of its later installation. The records show that the amplitudes and frequency contents of the signals are very different from one station to another (fig. 4). For instance, PMP and ROC are distant of 300 m, but the signal at PMP is about four times larger than at ROC. Also, the signal at CHA appears depleted in high frequencies compared to the others stations. The method used is a classical spectral ratio method with a reference station [Borcherdt, 1970]. It consists in determining the site amplification at each site with respect to a reference site located on the bedrock, thus poorly affected by site effects. This method is applied to the signal of local events, whose distance to the stations must be large compared to the interstation distance. The site response is computed by dividing the amplitude spectrum of a record at a station by the amplitude spectrum of the similar record at the reference station (see fig. 5, which describes the main steps of the method). The spectra are computed for the S-wave, which is more sensitive than the P-wave to sediment amplification. An important step is the smoothing of the spectra : it removes instabilities, but it may also remove resonance peaks which could have some physical significance (fig. 8). Spectral ratios are computed for both the vertical (V) and horizontal (H) components. H is a combination of the N-S and E-W components. We present logarithmic average ratios for each station, plus or minus one standard deviation. The reference station must be close to the other stations, it must be located on a rock outcrop of the same nature as the substratum beneath the other stations, and it must be free of site effect. An empirical way to check this last point is to analyse the H/V spectral ratio between the H and V components at a single station [Nakamura, 1989 ; Lermo and Chavez-Garcia, 1993] : this ratio is close to 1 in the absence of site effect [Le Brun, 1997]. It has been determined for stations CHA and ROC (fig.6). The choice of ROC as reference site is more appropriate, as the H/V ratio remains close to 1 at any frequency. The spectral ratios for the nine stations other than ROC (fig. 7) exhibit a great geographic variability of the amplifications : for example, at 20 Hz, the amplitude of the H-ratio is ten times greater at AUZ than at CHA, which is distant by less than 500 m. The results show that amplification and frequency variations are nearly similar for the H and V components : site effects affect both vertical and horizontal components. EDF and HOP, located on rock, do not show any amplification in the frequency range considered. CHA and CIT, also located on rock but with possible topographic effects, exhibit more complex spectral ratios. In particular, at CHA, the amplification decreases drastically for frequencies higher than 5 Hz. The other stations, which are on Quaternary structures, show peaks on the two components at frequencies between 6 and 10 Hz. However, on the horizontal component, the peak is generally at a lower frequency than on the vertical one (see PMP and AUZ, fig. 7). SAN is characterized by a high amplification over a large frequency band : on the horizontal component, the ratio is higher than 5 between 1.6 and 20 Hz and reaches 10 at 3 Hz. The results discussed here concern smoothed spectra, but the amplification at some particular frequencies may exceed the smoothed value by a factor 2 to 5. For instance, the PMP spectra show systematically a peak near 5.5 Hz (fig. 8), twice larger than the smoothed value. For this particular station located at the basement of a building, a soil-structure interaction may possibly explain the observed prominent peak. A similar effect is observed at GEN, which is also located at the bottom of a building. In order to know if some parameters, like the phase used, the magnitude, the epicentral distance or the back-azimuth, may influence the spectral ratios, we have performed various tests with the ratios obtained at PMP (fig. 9). It turns out that none of these parameters has an important influence on the spectral ratios obtained. If the structure is known, the site effects can be modelled with synthetic seismograms. The structure of the subsurface beneath the station SAN is known thanks to a seismic refraction experiment made on a 100 m-long profile. With a simple 1D-model, synthetic spectral ratios have been calculated with the reflectivity method [Müller, 1985] for a structure with sediment layers (SAN) compared to a structure without sediment layer (ROC). For the H-component, the resonance frequencies obtained with the model are quite similar to the observed ones, but the amplifications are about three times too low (fig. 10). This is also the case at station PMP, where the subsurface structure used in the model has been derived from empirical relationship between peak frequency and sediment layer thickness. On the other hand, the agreement is poor for the V-component. 2D and 3D effects, which are not taken into account here, may possibly explain this difference.
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Takada, Miho, Atsushi Otani, Ken Ogino, and Nagahisa Yoshimura. "Spectral-Domain Optical Coherence Tomography Findings in the Mizuo–Nakamura Phenomenon of Oguchi Disease." Retina 31, no. 3 (March 2011): 626–28. http://dx.doi.org/10.1097/iae.0b013e318206cd52.
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Massa, Marco, Gabriele Ferretti, Andrea Cevasco, Luana Isella, and Claudio Eva. "Analysis of Site Amplification Phenomena: An Application in Ripabottoni for the 2002 Molise, Italy, Earthquake." Earthquake Spectra 20, no. 1_suppl (July 2004): 107–18. http://dx.doi.org/10.1193/1.1768540.
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The geophysical working group of the University of Genoa conducted a field experiment to analyze site amplification effects in Ripabottoni, a village in the Molise region of Italy. We used both noise and earthquake recordings, combined with detailed geologic and geotechnical surveys, to define site amplification phenomena. The site effects determination was obtained using the Nakamura technique and the H/V spectral analysis applied to earthquake recordings. The results were validated by applying a one-dimensional simulation code. The computed spectral ratios point out three different typologies of site effects: the southern sector of Ripabottoni is characterized by an absence of local amplification phenomena; the central sector of the village shows a local amplification phenomena with a fundamental frequency of 4–6 Hz; and the northeastern side of the village shows a site response at a fundamental frequency between 2–3 Hz.
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Prastowo, Rizqi, Urip Nurwijayanto Prabowo, Rita Desiasni, Melfa Utari, and Fitri Puspasari. "PEMETAAN KETEBALAN LAPISAN SEDIMEN WILAYAH KLATEN DENGAN ANALISIS DATA MIKROTREMOR." KURVATEK 1, no. 2 (May 23, 2017): 49–54. http://dx.doi.org/10.33579/krvtk.v1i2.239.
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Daerah Klaten dan sekitarnya secara geologi tertutup oleh endapan fluvial vulkanik Merapi,sehingga identifikasi struktur geologi bawah permukaan tidak nampak. Penelitian ini bertujuan untuk memetakan kedalaman lapisan sedimen di dataran klaten. Metode yang digunakan adalah Horizontal to Vertical Spectral Ratio (Metode Nakamura) dan pengukuran dilakukan secara grid sebanyak 31 titik. Hasil analisis frekuensi natural antara 0,67 – 10,655 Hz dan pemetaan lapisan sedimen yaitu mencapai 80-90m di kecamatan Kalikotes tepatnya desa Mojayan, Desa Gumulan dan Desa Kalikotes, sedangkan ketebalan lapisan sekitar 5-15m sebagian besar berada pada kecamatan Klaten Utara. Potensi kerusakan akibat efek ketebalan ini berakibat pada peningkatan ground shaking di permukaan akbat mikrozonasi.
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Ibs-von Seht, Malte, and Jürgen Wohlenberg. "Microtremor measurements used to map thickness of soft sediments." Bulletin of the Seismological Society of America 89, no. 1 (February 1, 1999): 250–59. http://dx.doi.org/10.1785/bssa0890010250.
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Abstract The observations about the behavior of microtremor spectra presented here show that noise measurements can be used as a powerful tool to determine the thickness of soft cover layers. The most suitable method for this determination is Nakamura's technique, which is the ratio of the horizontal-component noise spectrum and that of the vertical component (H/V spectrum). The frequency of the main peak in these spectral ratios correlates well with the sediment thickness at the site. Using an extensive database of microtremor measurements carried out in the western Lower Rhine Embayment (Germany), it was possible to show that this correlation is clearly valid for a wide range of thickness, namely, from tens of meters to more than 1000 m. A simple formula was derived that, for the sediments to be found in the area investigated, directly calculates the cover thickness from the frequency of the main peak in the H/V spectrum. A comparison with calculated resonant frequencies suggests the relation derived from the noise measurements depending on the velocity depth function of the shear wave. Classical spectral ratios are shown to be strongly influenced by the noise level and are therefore less reliable in determining the resonant frequency of the subsoil. The practical relevance of the investigation is illustrated by means of cross sections, constructed from results of the microtremor analyses, which provide a convincing image of the surficial structure of the areas investigated.
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Seekins, Linda C., Leif Wennerberg, Lucia Margheriti, and Hsi-Ping Liu. "Site amplification at five locations in San Francisco, California: A comparison of S waves, codas, and microtremors." Bulletin of the Seismological Society of America 86, no. 3 (June 1, 1996): 627–35. http://dx.doi.org/10.1785/bssa0860030627.
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Abstract We compare microtremor data to weak-motion S-wave and coda recordings at sites in San Francisco in order to clarify the range of applicability of microtremor data to ground-motion prediction. We also compare S-wave results to coda results. For each type of data, we compute spectral ratios of motions from two soil/rock station pairs and from an uphole/downhole pair in the Marina district. We compute horizontal/vertical ratios (Nakamura's method) at a soil site, a rock site, and the surface and borehole instruments. In the station-pair analyses, microtremor data show amplifications at the same fundamental frequency as S waves, but the frequencies of other peaks do not agree. The amplification at frequencies higher than 2 Hz is greater in the microtremor data. Station-pair ratios of coda data generally show spectral peaks occurring at the same frequencies, but with levels varying from one to four times the amplification from S-wave ratios. Nakamura's method of analyzing microtremors agrees better with S-wave station-pair results than the microtremor station-pair method over a limited frequency band that varies from station to station.
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Tien, Hung Nguyen, Phuong Nguyen-Hong, Minh Nguyen-Le, Wen Kuo-Liang, and Nguyen Tran-An. "Investigation of microtremor motion variation by Nakamura’S H/V spectral ratio method." Tạp chí Khoa học và Công nghệ biển 17, no. 4B (December 15, 2017): 68–74. http://dx.doi.org/10.15625/1859-3097/17/4b/12994.
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In this study, the variation of microtremor motion is investigated using observation data in Hanoi and Vung Tau cities. The results of observation conducted by times and by seismometers are processed using the Nakamura's H/V spectral ratio method and compared. For investigation, the observations have been conducted with frequency of 27 observations per hour, 22 observations per month, 4 simultaneous observations using both Servo and K2 seismometers, and 12 simultaneous observation using 7 Servo seismometers. The results of data analysis show that the values of dominant frequency and shapes of the H/V spectral ratio obtained are similar in the frequency range from 0.4 Hz to 5 Hz, especially on the dominant frequency domain. The results confirm that the microtremor variation observations can be carried out with one observation time or by multiple seismometers.
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Turnbull, Michael L. "Relative seismic shaking vulnerability microzonation using an adaptation of the Nakamura horizontal to vertical spectral ratio method." Journal of Earth System Science 117, S2 (November 2008): 879–95. http://dx.doi.org/10.1007/s12040-008-0074-2.
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Helaly, Abdul L., and Mehedi A. Ansary. "Assessment of seismic vulnerability index of RAJUK area in Bangladesh using microtremor observations." Soils and Rocks 44, no. 2 (May 27, 2021): 1–13. http://dx.doi.org/10.28927/sr.2021.057420.
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Microtremor Horizontal to Vertical spectral ratio technique, also known as the Nakamura’s method is growing in status for site response analysis. 500 locations in RAJUK area (1530 km2) have been selected for microtremor observations. Microtremor data have been compiled and studied to estimate the predominant resonance frequency and H/V peak amplitude following the SESAME (2004) guideline. Finally, seismic vulnerability index of site soil using Nakamura’s technique has been determined from predominant resonance frequency and H/V peak amplitude parameter. The calculated seismic vulnerability index for the studied 500 locations varies between 0.16 and 7.28. The low seismic vulnerability index (Kg) value means that the areas are relatively stiff and underlain by substantial deposit of sediments. The relatively higher Kg values are spread in the soft alluvial deposit areas. The areas with high Kg values are considered as fragile zones that may initiate significant damage to infrastructure situated in those areas during an earthquake.
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Bouranta, E., F. Vallianatos, N. J. Hatzopoulos, I. Papadopoulos, and P. Gaganis. "Microtremor HVSR study of site effects in the urban area of the town of Mytilene, Lesvos (Greece) - Preliminary results." Bulletin of the Geological Society of Greece 47, no. 3 (December 21, 2016): 1081. http://dx.doi.org/10.12681/bgsg.10955.
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Mytilene is the capital of Lesvos, the eighth largest island in the Mediterranean Sea and the largest in the North Aegean. The region of North Aegean is a geotectonically complex area, because its geodynamic status is directly affected by the North Anatolian Fault Zone. In the present paper, microtremor data have been analyzedfor the city of Mytilene using Nakamura technique of Horizontal to Vertical Spectral Ratio (HVSR) to ascertain the structure in terms of the predominant frequency. 100 microtremor measurements have been performed in the city of Mytilene. At each point of microtremor measurement, the natural frequency and amplification factor have been determined. The predominant frequency varies from 0.4 Hz to 6.6 Hz. The amplification factor in 0.4-8.07 range has been obtained from the HVSR analysis. The results are presented in terms of maps, including the spatial variability of the predominant frequency and developed GIS database. The results of this study make it clear that the characteristics of microtremors depend on the type of soil deposits.
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HUPFER, THOMAS, HAJO LESCHKE, PETER MÜLLER, and SIMONE WARZEL. "EXISTENCE AND UNIQUENESS OF THE INTEGRATED DENSITY OF STATES FOR SCHRÖDINGER OPERATORS WITH MAGNETIC FIELDS AND UNBOUNDED RANDOM POTENTIALS." Reviews in Mathematical Physics 13, no. 12 (December 2001): 1547–81. http://dx.doi.org/10.1142/s0129055x01001083.
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The object of the present study is the integrated density of states of a quantum particle in multi-dimensional Euclidean space which is characterized by a Schrödinger operator with a constant magnetic field and a random potential which may be unbounded from above and from below. For an ergodic random potential satisfying a simple moment condition, we give a detailed proof that the infinite-volume limits of spatial eigenvalue concentrations of finite-volume operators with different boundary conditions exist almost surely. Since all these limits are shown to coincide with the expectation of the trace of the spatially localized spectral family of the infinite-volume operator, the integrated density of states is almost surely non-random and independent of the chosen boundary condition. Our proof of the independence of the boundary condition builds on and generalizes certain results obtained by S. Doi, A. Iwatsuka and T. Mine (Math. Z. 237 (2001) 335) and S. Nakamura (J. Funct. Anal. 173 (2001) 136).
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Panou, A. A., N. Theodulidis, P. M. Hatzidimitriou, C. B. Papazachos, and K. Stylianidis. "AMBIENT NOISE HORIZONTAL-TO-VERTICAL SPECTRAL RATIO FOR ASSESSING SITE EFFECTS IN URBAN ENVIRONMENTS: THE CASE OF THESSALONIKI CITY ( NORTHERN GREECE )." Bulletin of the Geological Society of Greece 36, no. 3 (January 1, 2004): 1467. http://dx.doi.org/10.12681/bgsg.16536.
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250 ambient noise measurements were performed in a dense grid (about 150mX150m) covering the historical center of the city of Thessaloniki (Northern Greece), that was strongly affected by the 20/6/1978 (M=6.5) damaging earthquake. The data were processed using the method of horizontal- to-vertical (H/V) spectral ratio (Nogoshi and Igarashi, 1971; Nakamura, 1989). In order to evaluate diurnal and seasonal variation (summer - winter) of the ambient noise H/V spectral ratio, systematic measurements were performed in eight sites. The fundamental frequency (fo) and the corresponding H/V amplitude level (Ao) from the ambient noise H/V spectral ratio for each site were calculated. Spatial interpolation of the fundamental frequency (fo) and the corresponding H/V amplitude level (Ao) was attempted between all points and respective contour maps were produced. Diurnal variation of the ambient noise H/V spectral ratio showed that it is preferable to perform measurements during the calm hours of a day, when manmade noise is relatively low. However, no systematic seasonal fluctuation effect on the ambient noise H/V spectral ratio was identified for the city of Thessaloniki. Contour maps of both fundamental frequency (fo) and corresponding H/V amplitude level (Ao) were compared versus the macroseismic data of the 1978 earthquake (Leventakis, 2003), as well as with related geological (IGME, 1978) and geotechnical (Anastasiadis et al., 2001) studies for the same area. Damage distribution due to 20/6/1978 earthquake (Penelis et al., 1985) was also converted to EMS_98 (European Macroseismic Scale, 1998). For seventy buildings, made of reinforced concrete, we have also compared the obtained results with the dynamic amplification of the buildings (Ubuilding) at the fundamental soil frequency (fo). The results encourage the use of ambient noise measurements along with the (H/V) spectral ratio technique as a nonexpensive and fast tool in microzonation studies to be carried out in urban environments.
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Riepl, J., P. Y. Bard, D. Hatzfeld, C. Papaioannou, and S. Nechtschein. "Detailed evaluation of site-response estimation methods across and along the sedimentary valley of volvi (EURO-SEISTEST)." Bulletin of the Seismological Society of America 88, no. 2 (April 1, 1998): 488–502. http://dx.doi.org/10.1785/bssa0880020488.
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Abstract Using records from the EURO-SEISTEST area near Thessaloniki (Greece), we studied empirically the amplification effects of a sedimentary valley. One of the main advantages of this site is the very detailed knowledge of the near-subsurface structure due to exhaustive geophysical and geotechnical measurements and data analyses (Jongmans et al., 1998). The uniqueness of the seismological data set is the very dense network: 31 stations were installed perpendicular and parallel to the valley axis, with minimum interstation distances of 250 m. The mean amplifications along both axes, estimated from 13 local events, were imaged using the traditional spectral ratio technique. Variations of the mean amplifications due to the choice of different data subsets were tested by the use of up to 89 local events, supplemented by four teleseismic events offering good low-frequency resolution. Results obtained using the traditional spectral ratio technique were compared with results from a generalized inversion technique, the H/V ratio technique, a coda wave technique, and Nakamura's technique. Advantages and disadvantages of each method are outlined, especially from a practical point of view.
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Brett, Genevieve Jay, Larry Pratt, Irina Rypina, and Peng Wang. "Competition between chaotic advection and diffusion: stirring and mixing in a 3-D eddy model." Nonlinear Processes in Geophysics 26, no. 2 (April 5, 2019): 37–60. http://dx.doi.org/10.5194/npg-26-37-2019.
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Abstract. The importance of chaotic advection relative to turbulent diffusion is investigated in an idealized model of a 3-D swirling and overturning ocean eddy. Various measures of stirring and mixing are examined in order to determine when and where chaotic advection is relevant. Turbulent diffusion is alternatively represented by (1) an explicit, observation-based, scale-dependent diffusivity, (2) stochastic noise, added to a deterministic velocity field, or (3) explicit and implicit diffusion in a spectral numerical model of the Navier–Stokes equations. Lagrangian chaos in our model occurs only within distinct regions of the eddy, including a large chaotic “sea” that fills much of the volume near the perimeter and central axis of the eddy and much smaller “resonant” bands. The size and distribution of these regions depend on factors such as the degree of axial asymmetry of the eddy and the Ekman number. The relative importance of chaotic advection and turbulent diffusion within the chaotic regions is quantified using three measures: the Lagrangian Batchelor scale, the rate of dispersal of closely spaced fluid parcels, and the Nakamura effective diffusivity. The role of chaotic advection in the stirring of a passive tracer is generally found to be most important within the larger chaotic seas, at intermediate times, with small diffusivities, and for eddies with strong asymmetry. In contrast, in thin chaotic regions, turbulent diffusion at oceanographically relevant rates is at least as important as chaotic advection. Future work should address anisotropic and spatially varying representations of turbulent diffusion for more realistic models.
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Del Gaudio, V., S. Coccia, J. Wasowski, M. R. Gallipoli, and M. Mucciarelli. "Detection of directivity in seismic site response from microtremor spectral analysis." Natural Hazards and Earth System Sciences 8, no. 4 (July 25, 2008): 751–62. http://dx.doi.org/10.5194/nhess-8-751-2008.
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Abstract. Recent observations have shown that slope response to seismic shaking can be characterised by directional variations of a factor of 2–3 or larger, with maxima oriented along local topography features (e.g. maximum slope direction). This phenomenon appears influenced by slope material properties and has occasionally been detected on landslide-prone slopes, where a down-slope directed amplification could enhance susceptibility to seismically-induced landsliding. The exact conditions for the occurrence of directional amplification remain still unclear and the implementation of investigation techniques capable to reveal the presence of such phenomena is desirable. To this purpose we tested the applicability of a method commonly used to evaluate site resonance properties (Horizontal to Vertical Noise Ratio – HVNR or Nakamura's method) as reconnaissance technique for the identification of site response directivity. Measurements of the azimuthal variation of H/V spectral ratios (i.e. between horizontal and vertical component) of ambient microtremors were conducted in a landslide-prone study area of central Italy where a local accelerometric network had previously provided evidence of directivity phenomena on some slopes. The test results were compared with average H/V spectral ratios obtained for low-to-moderate earthquakes recorded by the accelerometric stations. In general, noise and seismic recordings provided different amplitudes of spectral ratios at similar frequencies, likely because of differences in signal and instrument characteristics. Nevertheless, both kinds of recordings showed that at sites affected by site response directivity major H/V peaks have orientations consistent (within 20°–30°) with the direction of maximum shaking energy. Therefore, HVNR appears to be a promising technique for identifying seismic response directivity. Furthermore, in a comparative test conducted on a slope mantled in part by a deep-seated landslide we detected spectral peaks with orientations close to the maximum slope direction, whereas no evidence of directivity was found outside the slide boundaries. This indicates the influence of the landslide body on seismic response directivity.
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Kafadar, Ozkan. "A geophone-based and low-cost data acquisition and analysis system designed for microtremor measurements." Geoscientific Instrumentation, Methods and Data Systems 9, no. 2 (September 4, 2020): 365–73. http://dx.doi.org/10.5194/gi-9-365-2020.
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Abstract. The commercial data acquisition instruments designed for three-component microtremor measurements are usually very expensive devices. In this paper, a low-cost, computer-aided, and geophone-based system designed to record, monitor, and analyze three-component microtremor data is presented. This proposed system is not a simple data acquisition system. It is also an integrated system developed to interpret the microtremor data using the horizontal-to-vertical spectral ratio (H ∕ V) method without any external software. Therefore, the H ∕ V peak frequency and amplitude can be easily estimated using this system. The proposed system has several features such as a 200 Hz sampling frequency, approximately 72 dB dynamic range, text data format, and data analysis tools. This system consists of a graphical user interface developed by using the .NET Framework 4.5.2 and external hardware that includes signal conditioning circuits, voltage converter circuit, external analog-to-digital converter, and Arduino Uno board. The proposed system uses low-cost vertical and horizontal geophones with a 4.5 Hz natural frequency to measure three-component microtremor data. The developed software undertakes many tasks such as communication between the external hardware and computer, transferring, monitoring, and recording the seismic data to the computer, and interpretation of the recorded data using the Nakamura method. Channel consistency and internal noise measurement tests were performed to demonstrate the accuracy and precision of the proposed system. The proposed system was compared to a commercial triaxial digital seismograph, and satisfactory results were obtained. The developed system is a completely open-source and open-hardware system and can be easily used in academic studies conducted by researchers and university students who are interested in seismic ambient noise analysis.
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Khan, Sarfraz, Muhammad Waseem, Shahzad Khalid, Denise-Penelope N. Kontoni, Mahmood Ahmad, and Suraparb Keawsawasvong. "Fuzzy Clustering Analysis of HVSR Data for Seismic Microzonation at Lahore City." Shock and Vibration 2022 (October 28, 2022): 1–13. http://dx.doi.org/10.1155/2022/3109609.
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A microzonation study deals with the classification of hazards in a town or city in terms of surface ground motions that result from amplification and resonance frequency in soils against seismic tremors. This paper presents the result of a microzonation study in terms of resonance frequency and peak amplitude for Lahore city, Pakistan. In order to recognize the local soil effects of the covered geology at 159 sites in Lahore city, the horizontal-to-vertical spectral ratio (HVSR) Nakamura method was implemented. A fuzzy C-mean (FCM) clustering algorithm was adopted to obtain the best cluster solution of the analyzed HVSR parameters. The results of the Silhouette Index suggest that the FCM clustering solution of observation data points is more consistent. The results of clustering reveal three solutions. Clusters 1 and 2 reveal that a major part of the research area possesses low to moderate frequencies (0.66–1.03 Hz) with a peak amplitude of 2.25–4.38 mm, indicating the presence of soft to hard rock and thick alluvial sedimentary cover. Cluster 3 reveals the presence of soft to compact rocks (with frequencies and amplitudes of 0.73–1.03 Hz and 3.02–4.11 mm, respectively) overlaying the bedrock. Lahore city has 60% of soil cover with an amplitude of 2–3 mm (for the central part) and about 40% of 3–4 mm in the northern, southern, and southwest portions. According to the NEHRP soil classification code of 1997, a major part of the city has stiff nature of the soil, while a few places reveal the presence of very dense soil. The maps produced in this study will provide expected ground motion-related useful information to reduce the seismic risk for infrastructure in Lahore city.
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Del Gaudio, Vincenzo, Janusz Wasowski, Pierpaolo Pierri, Antonio Moretti, and Gianluca Ferrini. "Multitemporal analysis of ambient noise polarization to characterize site response in the town of Amatrice, shattered by the 2016 central Italy earthquake." Geophysical Journal International 224, no. 2 (September 18, 2020): 739–59. http://dx.doi.org/10.1093/gji/ggaa335.
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SUMMARY The Mw 6.0 earthquake that hit central Italy on 2016 August 24 caused an abnormally high level of destruction in the town of Amatrice. In order to clarify the role of site response in causing such a disaster, a series of ambient noise recordings acquired in the aftermath of the event are analysed here to identify site resonance properties from the ratios H/V between horizontal and vertical amplitudes of ground motion. Although the noise data acquisition was limited by the emergency management activities, the use of a new analysis technique, which isolates the contribution of Rayleigh waves to the noise wavefield and averages instantaneous estimates of H/V ratios, provided more stable results compared to the standard Nakamura's technique based on mean spectral ratios. The results demonstrated the occurrence of significant resonance phenomena, but without an obvious correlation with the spatial distribution of damage severity. It is apparent that the damage severity was also influenced by some additional local factors related to building vulnerability. Moreover, the time-series analysis revealed seasonal variations in the Rayleigh wave ellipticity curves likely related to the water content changes in the surface deposits and their influence on the Poisson coefficient. Finally, the new method proved capable of recognizing time-varying directions of Rayleigh wave propagation. This capability could be exploited to support other passive seismic methods (e.g. ReMi), whose results’ reliability is limited by the lack of control on wave direction origin.
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Duong, Nguyen Anh, Pham Dinh Nguyen, Vu Minh Tuan, Bui Van Duan, and Nguyen Thuy Linh. "Seismic hazard assessment and local site effect evaluation in Hanoi, Vietnam." Tạp chí Khoa học và Công nghệ biển 17, no. 4B (December 15, 2017): 82–95. http://dx.doi.org/10.15625/1859-3097/17/4b/12996.
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In this study, we have carried out the probabilistic seismic hazard analysis in Hanoi based on the latest seismotectonic data. The seismic hazard map shows peak ground acceleration values on rock corresponding to the 10% probability of exceedance in a 50-year time period (approximately return periods of 500 years). The calculated results reveal that the maximum ground acceleration can occur on rock in Hanoi is about 0.13 g corresponding to the shaking intensity level of VIII on the MSK-64 scale. The ground motion values calculated on rock vary according to the local site conditions. We have evaluated and corrected the local site effects on ground motion in Ha Dong district, Hanoi by using microtremor and borehole data. The Nakamura’s H/V spectral ratio method has been applied to establish a map of ground dominant periods in Ha Dong with a TS range of 0.6 - 1.2 seconds. The relatively high values of periods indicate that Ha Dong has soft soil and thick Quaternary sediments. The sediment thickness in Ha Dong is calculated to vary between 30 - 75 m based on ground dominant periods and shear wave velocity VS30 = 171 - 254 m/s. The results of local site effect on ground motion show that the 500-year return period peak ground acceleration in Ha Dong ranges from 0.13 g to 0.17 g. It is once again asserted that the seismic hazard in Hanoi is a matter of great concern, due not only to the relatively high ground acceleration, but also to the seismic characteristics of soil (low shear wave velocity, ground dominant period of approximately 1 second).
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Ortiz-Alemán, Carlos, Maricarmen Reyes-Olvera, Arturo Iglesias-Mendoza, Mauricio Gabriel Orozco-Del-Castillo, and Jorge Hernández-Gómez. "Estimation of source, path and site effects at MASE array stations: a comprehensive study." Geofísica Internacional 56, no. 1 (January 1, 2017). http://dx.doi.org/10.22201/igeof.00167169p.2017.56.1.1748.
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A parameterized source and path effects inversion method based on the use of global optimization techniques is presented. We applied this method on velocity data from various seismic events collected between August, 2005 and April, 2007 in Mexico by the regional MesoAmerican Subduction Experiment (MASE) seismic network and other stations from the permanent Mexican Seismological Survey Network (SSN). The source, path and site parameters corresponding to the S wave amplitude spectra of 219 velocity seismic records (162 from MASE and 57 from SSN) were estimated by means of a generalized inversion approach. The simultaneously inverted parameters from the records of 55 stations shows a significant agreement between the observed and calculated spectra, which supports their realiability. Nakamura’s method was used to compute an initial guess for the generalized inversion. Comparisons between Nakamura’s technique and parameterized source and path effects inversion by using simulated annealing method were also established. Finally, a frecuency dependent attenuation relationship for the study area was computed by using a genetic algorithm inversion approach.
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E. Giampiccolo, S. Gresta, M. Mucciarelli, G. De Guidi, and M. R. Gallipoli. "Information on subsoil geological structure in the city of Catania (Eastern Sicily) from microtremor measurements." Annals of Geophysics 44, no. 1 (February 18, 2001). http://dx.doi.org/10.4401/ag-3606.
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Nakamuras technique, or the H/V spectral ratio method, has been applied to microtremor measurements carried out in the urban area of Catania (Eastern Sicily) to obtain information on the geological structure of some sites,and to make a hypothesis on their seismic response. In general, sites located on soft soils or anthropic debris fillings have shown greater amplification at high frequencies (above 1 Hz). However, a strong lateral variation was observed in the frequency band, thus a denser grid of measurement points is necessary for a precise mapping of the resonant frequencies. In the low frequency range, between 0.1 and 1 Hz, a common peak around 0.2 Hz was observed. The fundamental resonant frequency inferred from the main peak in the H/V spectrum has been used to calculate the depth of the interface between the clays and the main reflector on the basis of the shear-wave velocity: it has been estimated as about 700 m.
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Nguyen-Tien, Hung, Phuong Nguyen-Hong, Minh Nguyen-Le, Lin Che-Min, Nguyen Tran-An, Truyen Pham-The, and Duong Nguyen-Van. "Establishment of the correlation between the near-surface sedimentary thickness and the microtremor dominant frequency in the Hanoi area." Vietnam Journal of Earth Sciences, October 10, 2022. http://dx.doi.org/10.15625/2615-9783/17569.
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This paper established the correlation between the near-surface sedimentary thickness (D) and the microtremor dominant frequency (F0) in the Hanoi area based on 64 microtremor measuring points at the boreholes with depth to bedrock. The microtremor dominant frequency was determined using the horizontal-to-vertical (H/V) spectral ratio of the seismic noise technique proposed by Nakamura (1989). The near-surface sedimentary thickness was determined according to the borehole data from the previously published reports. The non-linear regression method was applied to the pairs of D and F0 values from 64 boreholes to obtain the relationship of form D = 81.851*F0-0.942. This correlation function was used to determine the values of the near-surface sedimentary thickness at microtremor measurement points according to the F0 values. Comparison of the D-values obtained in this study with those from the boreholes data shows good coincidence by values and variation tendency, especially in areas with shallow cover thickness from 50 to 100 m. The above results allow the proposal of a new near-surface sedimentary thickness determination technique in the Hanoi area.
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Kyaw, Zaw Lin, Subagyo Pramumijoyo, Salahuddin Husein, Teuku Faisal Fathani, and Junji Kiyono. "GROUND MOTION IN YOGYAKARTA CITY, YOGYAKARTA SPECIAL PROVINCE, INDONESIA ON DENSELY MICROTREMOR OBSERVATIONS AND SHEAR WAVE VELOCITY." Journal of Applied Geology 5, no. 1 (September 2, 2015). http://dx.doi.org/10.22146/jag.7203.
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Microtremor is currently considered the foremost tool in site effect studies. The ground motion is estimated with microtremor observations, meaning that subsoil mechanical properties and geometry are evaluated and from them an estimate of local amplification is computed. Here, the ground motion is studied by the site effects of seismic hazard zonation of urban areas in Yogyakarta City. The main purpose of this paper is zoning the geological engineering features and assessing seismic of the research urban area. In this regard, the microtremors are measured at 274 sites by single station sampling method and Nakamura technique. The microtremors of all over the city are processed by a model of Mitutoyo-GPL-6A3P. The amplification factor generally ranges between 0.70 and 5.56 and the natural frequency normally varies between 0.40 and 3.30 Hz. The information layers are prepared in GMT used for detecting the zonation of potential seismic hazard. The shear wave velocity is calculated in 12 existing drilling sites based on the geotechnical approach of SPT for soil condition. To study the ground motion, geological engineering condition is investigated using amplification factor, natural frequency, shear wave velocity maps which are analyzed using densely single microtremor observation and SPT from existing drilling sites. Keywords: Ground motion, amplification factors, natural frequency; H/V spectral ratio, microtremor observations, Yogyakarta Urban
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Deng, Zhen, Fangli Fan, Danyan Tang, Yifeng Wu, Yujie Shu, and Kunlin Wu. "A compound heterozygous mutation in the S-Antigen Visual Arrestin SAG gene in a Chinese patient with Oguchi type one: a case report." BMC Ophthalmology 22, no. 1 (March 4, 2022). http://dx.doi.org/10.1186/s12886-022-02307-z.
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Abstract Background Oguchi disease is a rare autosomal recessive form of congenital quiescent night blindness. Oguchi disease has been found to be associated with gene mutations in SAG and GRK1, which are vital factors in the recovery phase of phototransduction after light stimuli. We report a case of Oguchi disease with novel heterozygous mutations in SAG. Case presentation A 7-year-old girl with a history of night blindness since childhood, was referred to our hospital. Ophthalmologic examinations included visual acuity, fundus examinations, fundus photography, spectral-domain optical coherence tomography, electroretinographic (ERG). Mutation screening of the SAG and GRK1 genes was performed. This patient exhibited typical clinical characteristics of Oguchi disease, including night blindness, golden fundus with the Mizuo–Nakamura phenomenon, packed structure of the parafovea in optical coherence tomography and reduced a-waves and b-waves in scotopic 3.0 ERG. Genetic testing revealed a heterozygous change in nucleotide c.72_75+15delATCGGTGAGTGGTGCACAA in exon 2 of the SAG gene in this patient, her unaffected mother and younger brother. A splicing alteration of nucleotide c.376-2A>C was identified in exon 6 of the SAG gene with heterozygous status in this patient and her unaffected father. Conclusions Compound heterozygosity of a nonsense p.S25X mutation in exon 2 and a splicing alteration in exon 6 of the SAG gene is the cause of this patient with Oguchi type 1 disease in China.
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Chao, L. L., G. S. Cargill, C. Kothandaraman, D. Cyr, G. Flynn, E. S. Hellman, D. Wiesmann, D. N. E. Buchanan, and I. Brener. "Nonuniform Morphology and Luminescence Properties of a Molecular Beam Epitaxy GaN Film from Atomic Force Microscopy, Scanning Electron Microscopy and Cathodoluminescence." MRS Internet Journal of Nitride Semiconductor Research 2 (1997). http://dx.doi.org/10.1557/s1092578300001332.
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Complex faceted features of micrometer sizes and with intense luminescence rise 200-300 nm above the surface of a GaN thin film grown by molecular beam epitaxy on (0001) sapphire. Cathodoluminescence measurements at room temperature and at 8K were used to investigate the luminescence properties of these microfeatures in comparison with those of the background GaN material. The morphology of the micro-features was studied by scanning electron microscopy and by atomic force microscopy.GaN and related compounds have been considered as promising materials for light emitting devices in the short wavelength visible and UV spectral regions because of their direct, wide band gaps and high luminescence efficiency. Remarkable, rapid success has been achieved in developing devices based on III-V nitrides, which allows these material systems to rival other systems under development [1]. Blue-green LEDs fabricated from InGaN/AlGaN double-heterostructure layers on sapphire substrates by Nichia Chemical Industries in Japan are commercially available, despite the presence of high extended defect densities in the 1010 /cm2 range [2]. In December 1995, an important milestone in the development of nitride lasers was reached; Nakamura et al. in Nichia demonstrated the first nitride-based laser diode which operated at 417 nm under pulsed conditions at room temperature [3].The morphology and spatial distribution of luminescence in GaN thin films have been investigated by several research groups [4], [5], [6], although most efforts have been directed to developing appropriate growth conditions for improved film quality. From observations by scanning electron microscopy (SEM) and atomic force microscopy (AFM), Trager-Cowan et al. described an MBE-grown GaN film which contained an assembly of oriented hexagonal crystallites rising above a background of polycrystalline or amorphous material [4]. All the crystallites, oriented in a similar fashion, had roughly the same sizes, 1 or 2 μm across a hexagonal face and about 1 μm high. These crystallites were much brighter than the surrounding background material in panchromatic low-temperature cathodoluminescence (CL) images. Trager-Cowan et al. concluded that the crystallites were of better quality than the background material. They also observed a green emission band, attributed to impurities, which became weaker for higher electron beam voltages, generating luminescence from deeper in the film. From this observation, they concluded that higher quality material is located closer to the film's outer surface. Spatial variation of the luminescence efficiency from MOCVD-grown films has also been observed by Ponce et al[5]. in their room-temperature CL microscopy studies. Their results showed significant nonuniformities in both the band-edge and yellow band emissions. Although they reported no faceted island structures, one of their samples had “marked surface features” and consisted of hexagonal crystals 10 to 50 μm in diameter. The crystals gave strong band-to-band (364 nm) luminescence.In this paper, the morphology of a GaN film grown on (0001) sapphire by MBE is characterized by SEM and AFM, and CL measurements are used to investigate the luminescence properties of the film at room temperature and at 8K. Some regions of this film are similar to the one described by Trager-Cowan et al. [4] in having micron sized, brightly luminescent islands. The hexagonal facet angles and bright luminescence of islands in our film also resemble the larger scale, more regularly shaped hexagonal crystals of Ponce et al. [5]. These regions lie on the boundary of excess gallium growth conditions. Our results differ from those of Trager-Cowan in terms of the island morphologies and the spectral character of luminescence from the islands and from the background material. Possible causes of the large variations in luminescence efficiency are discussed.