Academic literature on the topic 'Seismic sequences'

Penelitian geofisika di Perairan Todak, Singkep, Kepulauan Riau menggunakan seperangkat peralatan seismik pantul dangkal saluran tunggal. Tujuan penelitian ini adalah untuk menunjang penelitian keterdapatan endapan plaser pembawa timah dan unsur tanah jarang (REE). Hasil interpretasi rekaman seismik diperoleh terdapatnya lembah/mangkuk yang terbentuk secara alami akibat adanya terobosan batuan granit, di mana lembah/mangkuk-mangkuk ini merupakan tempat terjadinya sedimentasi dari hasil pelapukan batuan di sekitarnya. Hasil interpretasi rekaman seismik pantul saluran tunggal analog di perairan Todak, Singkep, dapat diklasifikasikan menjadi 3 runtunan yaitu runtunan A, B, dan runtunan C.Kata kunci Data seismik, endapan plaser, lembah/mangkuk, Perairan Todak. Geophysical research at Todak, Singkep, Riau Archipelago Province, by using single channel sahllow seismic refletion. The purpose of research is to support placer deposit bearing tin and rare earth element research at this area. From seismic interpretation can be recognized the distribution of valley/bowls which is naturally formed, caused by granite rock intrusion. Those valleys are sedimentation places of wheathered rock from the surrounding area. Beside that, the seismic research also for determining the placer deposit thickness. Interpratation of analog single channel seismic records in the Todak waters, Singkep, result 3 seismic sequences and intrusive feature, A sequences, B, and C. Keywords: Seismic data, placer deposit, valley/basin, Todak Watres.

During the last 20 years (1997 to 2017), four seismic sequences with Mw ≥ 5.5 mainshocks nucleated along the Central and Northern Apennines chain (Italy), causing casualties and damage: the 1997 Colfiorito, the 2009 L’Aquila, the 2012 Emilia, and the most recent 2016–2017 Central Italy seismic sequences. In this work, we perform a novel joint analysis of seismological and remote-sensing data to achieve new insights into the faulting process evolution during the considered seismic sequences. To this aim, we study these seismic sequences by exploiting the available seismological data and by applying fractals theory to them. In particular, we characterize the different behavior of compressional and extensional seismic sequences by examining the temporal evolution of the fractal dimension values. In addition, we compare the Differential Synthetic Aperture Radar Interferometry (DInSAR) displacement maps relevant to the considered seismic events (already published in our past papers) and the performed spatial and temporal seismological analyses, in order to emphasize some significant aspects of the different faulting processes active during these Italian seismic sequences. The analysis of the fractal dimension values shows that over time extensional seismic sequences are spatially distributed within a volume, whereas compressional ones are aligned along a preferential surface. These spatio-temporal patterns are confirmed by: (1) the spatial distribution of hypocenters for the events that occurred between the mainshock and the post-seismic synthetic aperture radar (SAR) acquisition; (2) the spatial extension of coseismic DInSAR ground-deformation patterns. The proposed seismic and ground-deformation analyses can thus typify different geodynamic contexts in Italy, providing a distinct image of articulated faulting processes.

We investigate the time dynamics of sequences of earthquakes occurred in three different seismic zones in Italy. All the series analyzed present 1/f α temporal fluctuations, shown by the power-law behaviour of several statistics (Fano Factor, Allan Factor and Count-based Periodogram), that allow to detect correlation properties in point processes.

Sequence Stratigraphic Analysis is claimed to be a “new globally valid system of stratigraphy … a precise methodology to subdivide, correlate and map sedimentary rocks” (Vail et al., 1991, p. 622). Sequence stratigraphic units, such as depositional sequences, depositional systems tracts, and parasequences, are time-equivalent rocks of specific durations controlled by cyclical changes in sediment supply related to eustasy. These units are bounded by regionally extensive unconformities with erosion beneath and onlapping strata above, or by physical surfaces separating either different patterns of stratal geometry or shoaling-up facies units. According to this school, precise correlations are based upon inferred time relations within depositional models.Several key concepts of sequence stratigraphy have their origins in early geological studies. For many years geologists have separated time-equivalent strata by regional unconformities related to changes in climate or sea level, e.g., J. Woodward, 1695 and T. C. Chamberline, 1909. Stratal surfaces, such as bentonites and limestone markers, have been used in place of fossils for time correlations since the first wells were drilled. Stratigraphic models have strongly influenced how we correlate strata since the time of William Smith.Two developments are, indeed, new and have sparked the current resurgence in stratigraphic research. One is the seismic technology to test the physical continuity of strata on a regional scale (50-100 km), and to test the stratal geometry of genetically related depositional packages. The second is the chart of global coastal onlap events and eustasy (Haq et al., 1988).Some key research problems are: (1) how to identify unique, time-significant stratal surfaces; (2) how to test their physical continuity; (3) how to test the time relations within depositional models; and (4) how to identify the unique, time-significant global events recorded in the stratigraphic record. These stratigraphic concepts can be tested by graphic correlation, which is a powerful technique of high precision, quantitative stratigraphy. Its application in Cretaceous sections of the Gulf Coast and Oman, and in the Plio-Pliestocene of the Gulf Coast aids the distinction between synchronous surfaces and diachronous boundaries.

Study on multi-channel seismic records from South Batanta Basin, West Papua acquired during RV Geomarin III cruise in 2013 were aimed to invent and map geological aspects and for geo-tectonic and geological history studies. Seismic data indicate that sediment sequences which can be observed from our seismic system in the study area are characterized by pre-extension sediments (Lower Early Miocene-Upper Early Pliocene), syn-extension sediments (Lower Middle Pliocene-Upper Late Pliocene), post-extension sediments (Early Pleistocene), and syn-inversion sediments (Late Pleistocene-Recent) typical of the West Papua tectonic system. In the study area, sediment sequences are possibly characterized by clastical sedimentary cover such as slumps, debrites and turbidites. Key words: South Batanta Basin, seismic sequence, tectonic, faults, clastical sediments. Studi rekaman seismik multi kanal dari Cekungan Batanta Selatan, Papua Barat yang diperoleh selama pelayaran KR Geomarin III pada tahun 2013 bertujuan untuk menginventarisir dan memetakan aspek-aspek geologi serta untuk studi geo-tektonik dan sejarah geologi. Data seismik menunjukkan bahwa urutan sedimen yang dapat diamati dari sistem seismik di daerah studi ditandai oleh sedimen pra-ekstensi (Miosen Awal Bagian Bawah-Pliosen Awal Bagian Atas), sedimen syn-ekstensi (Pliosen Tengah Bagian Bawah-Pliosen Akhir Bagian Atas), sedimen post-ekstensi (Plestosen Awal), dan sedimen syn-inversi (Pleistosen Akhir-Resen) tipikal sistem tektonik Papua Barat. Di daerah studi, urutan sedimen dicirikan oleh sedimen penutup klastika kemungkinan berupa slump, debrit dan turbidit. Kata kunci: Cekungan Batanta Selatan, sekuen seismik, tektonik, sesar, sedimen klastika.

There are six sedimentary seismic sequences overlying pre-Mesozoic basement in the Mesozoic-Cenozoic sedimentary cover of the Arctic regions of West Siberia and the Kara Sea shelf. The paper describes the seismic markers characteristics and the seismic-facial features of the Paleozoic, Triassic, Jurassic, Neocomian, Apt-Cenomanian and TuronianCenozoic seismic sequences. It was concluded that the features of large Cenomanian gas pools are seismic markers associated with gas-water contacts; Apt-Albian pools are displayed on time sections by a bright spot seismic anomaly.

Seismic reflection profiles from the Makassar basin have been analysed in terms of seismic stratigraphy. Systematic patterns of reflection terminations indicate the existence of at least three surfaces of discontinuity across the profiles-designated in order of superposition as C1, C2 and C3 - which define the boundaries of four seismic sequences, ie. :- seismic sequence I : topped by C1- seismic sequence II : the interval between C1 and C2- seismic sequence III : the interval between C2 and C3- seismic sequence IV : the interval between Cz and the sea floor Seismic sequence II is dominated by basin slope and basin floor seismic facies whereas seismic sequences II and IV consist of mainly shelf and shelf margin seismic facies. Correlation of seismic sequences with well data facilitates the exposition of basin development, The Late Cretaceous-early Tertiary regional uplift and erosion produced a major unconformity C1, upon which the transgressive facies of seismic sequence II was deposited. A lowstand of sea level due to the so-called intra-Mio- cene orogeny occurred in the upper Early Miocene and produced the C2. Deposition of seismic sequence III is marked by a relative rise of sea level, probably followed by another lowstand of sea level during Mio-Pliocene which formed the C3. The final event is an overall transgression and deposition of seismic sequence IV, with a possible minor lowstand of sea level in Pliocene-Recent, The occurrence of basin slope and basin floor seismic facies within seismic sequence II suggests that in the pre-Lower Miocene, basin subsidence was slightly greater than the rate of depositions. Since Lower Miocene both subsidence and sedimentation rates were equal and the deposition of shelf and shelf margin seismic facies of seismic sequences III and IV was prevailed in the basin.

This study investigates the potential relation of seismic anisotropy measured by surface seismic and the sealing potential of the shale sequences. Two case studies analyzed such a relationship. The Gippsland basin and Exmouth sub-basin are both hosts to prolific hydrocarbon resources and offer plenty of seismic data and sealing potential measurements. Weak anisotropy parameters extracted from carefully reprocessed seismic data show in both cases a positive correlation between sealing capacity and anisotropy of the shale.

Tesis para optar al grado de Doctor en Ingeniería de Minas
Una característica común en la minería que se realiza en roca competetente es la sismicidad inducida. Esta es resultado de los cambios en los esfuerzos y el fallamiento de la roca alrededor de las excavaciones mineras. Posterior a un evento sísmico, existe un aumento en los niveles de sismicidad que gradualmente decaen con el tiempo, conocido como una secuencia de réplicas. Restringir el acceso a las áreas de la mina por el tiempo suficiente que permita que ocurra este decaimiento de los eventos sísmicos es el enfoque principal de los protocolos de re entrada. Las propiedades estadísticas de las secuencias de réplicas pueden ser estudiadas mediante tres relaciones o leyes sísmicas: (1) Ley de Gutenberg Richter, (2) Ley de Omori Modificada (MOL) para el decaimiento temporal de la sismicidad, y (3) Ley de Båth para la magnitud de la réplica de mayor magnitud. Esta tesis contiene tres partes principales: estimación y correlaciones de los parámetros de las leyes sísmicas para secuencias de réplicas inducidas por la minería, desarrollo de protocolos de re entrada en el espacio tiempo magnitud y el reconocimiento y comportamiento temporal de secuencias de réplicas usando un aglomeramiento espacio tiempo. En la primera parte, se aplicaron las tres leyes sísmicas, además del modelo estocástico de Reasenberg Jones, para estudiar los parámetros de 11 secuencias sísmicas inducidas por la minería en cuatro minas en Ontario, Canadá. Para proporcionar directrices para el desarrollo del protocolo de re entrada, se estudió y aplicó la dependencia de esto parámetros con la magnitud del evento sísmico principal de la secuencia sísmica. Los resultados obtenidos son coincidentes con los que diferentes autores han estimado en sismicidad tectónica. Sin embargo, aparecen algunas "diferencias de escala", especialmente con el valor b de Gutenberg Richter y el valor p de la ley modificada de Omori, encontrando que, en promedio, hay diferencias de +0.35 y -0.2 respectivamente entre los resultados de la sismicidad inducida y tectónica. La segunda parte corresponde al desarrollo de un protocolo estocástico de re entrada en el espacio tiempo magnitud, utilizando las relaciones entre los parámetros sísmicos inducidos y la magnitud del evento principal. Se define un radio de exclusión y una relación entre el tiempo de máxima curvatura y la magnitud del evento principal. Esto permite construir curvas de decaimiento sísmico, proporcionando información sobre los patrones de decaimiento de una secuencia en curso. Finalmente, se propone un rango de probabilidad de ocurrencia de la réplica de mayor magnitud, basado en el modelo de probabilidad de Reasenberg Jones. La última parte consiste en analizar el comportamiento del agrupamiento de la sismicidad inducida por la minería a través del tiempo y el espacio. Usando el criterio estadístico de Akaike para seleccionar los parámetros del aglomeramiento espacio tiempo, fue posible identificar una secuencia de réplicas asociada a un evento principal con magnitud Mw = 0.7. Además, se encontró que la distancia espacio tiempo aparentemente disminuye su valor antes de que ocurra un evento principal, para luego retornar a su valor normal. Todos los hallazgos anteriores proporcionan una aproximación a pautas concisas y bien justificadas para el desarrollo del protocolo de re entrada.

The present study has been carried out with the following objectives: i) To investigate the attributes of source parameters of local and regional earthquakes; ii) To estimate, as accurately as possible, M0, fc, Δσ and their standard errors to infer their relationship with source size; iii) To quantify high-frequency earthquake ground motion and to study the source scaling. This work is based on observational data of micro, small and moderate -earthquakes for three selected seismic sequences, namely Parkfield (CA, USA), Maule (Chile) and Ferrara (Italy). For the Parkfield seismic sequence (CA), a data set of 757 (42 clusters) repeating micro-earthquakes (0 ≤ MW ≤ 2), collected using borehole High Resolution Seismic Network (HRSN), have been analyzed and interpreted. We used the coda methodology to compute spectral ratios to obtain accurate values of fc , Δσ, and M0 for three target clusters (San Francisco, Los Angeles, and Hawaii) of our data. We also performed a general regression on peak ground velocities to obtain reliable seismic spectra of all earthquakes. For the Maule seismic sequence, a data set of 172 aftershocks of the 2010 MW 8.8 earthquake (3.7 ≤ MW ≤ 6.2), recorded by more than 100 temporary broadband stations, have been analyzed and interpreted to quantify high-frequency earthquake ground motion in this subduction zone. We completely calibrated the excitation and attenuation of the ground motion in Central Chile. For the Ferrara sequence, we calculated moment tensor solutions for 20 events from MW 5.63 (the largest main event occurred on May 20 2012), down to MW 3.2 by a 1-D velocity model for the crust beneath the Pianura Padana, using all the geophysical and geological information available for the area. The PADANIA model allowed a numerical study on the characteristics of the ground motion in the thick sediments of the flood plain.

The present study has been carried out with the following objectives: i) To investigate the attributes of source parameters of local and regional earthquakes; ii) To estimate, as accurately as possible, M0, fc, Δσ and their standard errors to infer their relationship with source size; iii) To quantify high-frequency earthquake ground motion and to study the source scaling. This work is based on observational data of micro, small and moderate -earthquakes for three selected seismic sequences, namely Parkfield (CA, USA), Maule (Chile) and Ferrara (Italy). For the Parkfield seismic sequence (CA), a data set of 757 (42 clusters) repeating micro-earthquakes (0 ≤ MW ≤ 2), collected using borehole High Resolution Seismic Network (HRSN), have been analyzed and interpreted. We used the coda methodology to compute spectral ratios to obtain accurate values of fc , Δσ, and M0 for three target clusters (San Francisco, Los Angeles, and Hawaii) of our data. We also performed a general regression on peak ground velocities to obtain reliable seismic spectra of all earthquakes. For the Maule seismic sequence, a data set of 172 aftershocks of the 2010 MW 8.8 earthquake (3.7 ≤ MW ≤ 6.2), recorded by more than 100 temporary broadband stations, have been analyzed and interpreted to quantify high-frequency earthquake ground motion in this subduction zone. We completely calibrated the excitation and attenuation of the ground motion in Central Chile. For the Ferrara sequence, we calculated moment tensor solutions for 20 events from MW 5.63 (the largest main event occurred on May 20 2012), down to MW 3.2 by a 1-D velocity model for the crust beneath the Pianura Padana, using all the geophysical and geological information available for the area. The PADANIA model allowed a numerical study on the characteristics of the ground motion in the thick sediments of the flood plain.

Forecasting the time, location, nature, and scale of volcanic eruptions is one of the most urgent aspects of modern applied volcanology. The reliability of probabilistic forecasting procedures is strongly related to the reliability of the input information provided, implying objective criteria for interpreting the historical and monitoring data. For this reason both, detailed analysis of past data and more basic research into the processes of volcanism, are fundamental tasks of a continuous information-gain process; in this way the precursor events of eruptions can be better interpreted in terms of their physical meanings with correlated uncertainties. This should lead to better predictions of the nature of eruptive events. In this work we have studied different problems associated with the long- and short-term eruption forecasting assessment. First, we discuss different approaches for the analysis of the eruptive history of a volcano, most of them generally applied for long-term eruption forecasting purposes; furthermore, we present a model based on the characteristics of a Brownian passage-time process to describe recurrent eruptive activity, and apply it for long-term, time-dependent, eruption forecasting (Chapter 1). Conversely, in an effort to define further monitoring parameters as input data for short-term eruption forecasting in probabilistic models (as for example, the Bayesian Event Tree for eruption forecasting -BET_EF-), we analyze some characteristics of typical seismic activity recorded in active volcanoes; in particular, we use some methodologies that may be applied to analyze long-period (LP) events (Chapter 2) and volcano-tectonic (VT) seismic swarms (Chapter 3); our analysis in general are oriented toward the tracking of phenomena that can provide information about magmatic processes. Finally, we discuss some possible ways to integrate the results presented in Chapters 1 (for long-term EF), 2 and 3 (for short-term EF) in the BET_EF model (Chapter 4).

Forecasting the time, location, nature, and scale of volcanic eruptions is one of the most urgent aspects of modern applied volcanology. The reliability of probabilistic forecasting procedures is strongly related to the reliability of the input information provided, implying objective criteria for interpreting the historical and monitoring data. For this reason both, detailed analysis of past data and more basic research into the processes of volcanism, are fundamental tasks of a continuous information-gain process; in this way the precursor events of eruptions can be better interpreted in terms of their physical meanings with correlated uncertainties. This should lead to better predictions of the nature of eruptive events. In this work we have studied different problems associated with the long- and short-term eruption forecasting assessment. First, we discuss different approaches for the analysis of the eruptive history of a volcano, most of them generally applied for long-term eruption forecasting purposes; furthermore, we present a model based on the characteristics of a Brownian passage-time process to describe recurrent eruptive activity, and apply it for long-term, time-dependent, eruption forecasting (Chapter 1). Conversely, in an effort to define further monitoring parameters as input data for short-term eruption forecasting in probabilistic models (as for example, the Bayesian Event Tree for eruption forecasting -BET_EF-), we analyze some characteristics of typical seismic activity recorded in active volcanoes; in particular, we use some methodologies that may be applied to analyze long-period (LP) events (Chapter 2) and volcano-tectonic (VT) seismic swarms (Chapter 3); our analysis in general are oriented toward the tracking of phenomena that can provide information about magmatic processes. Finally, we discuss some possible ways to integrate the results presented in Chapters 1 (for long-term EF), 2 and 3 (for short-term EF) in the BET_EF model (Chapter 4).

Muds and mudstones are the most abundant sediments in sedimentary basins and can control fluid migration and pressure. In petroleum systems, they can also act as source, reservoir or seal rocks. More recently, the sealing properties of mudstones have been used for nuclear waste storage and geological CO2 sequestration. Despite the growing importance of mudstones, their geological modelling is poorly understood and clear quantitative studies are needed to address 3D lithology and flow properties distribution within these sediments. The key issues in this respect are the high degree of heterogeneity in mudstones and the alteration of lithology and flow properties with time and depth. In addition, there are often very limited field data (log and seismic), with lower quality within these sediments, which makes the common geostatistical modelling practices ineffective. In this study we assess/capture quantitatively the flow-important characteristics of heterogeneous mud-rich sequences based on limited conventional log and post-stack seismic data in a deep offshore West African case study. Additionally, we develop a practical technique of log-seismic integration at the cross-well scale to translate 3D seismic attributes into lithology probabilities. The final products are probabilistic multiattribute transforms at different resolutions which allow prediction of lithologies away from wells while keeping the important sub-seismic stratigraphic and structural flow features. As a key result, we introduced a seismically-driven risk attribute (so-called Seal Risk Factor "SRF") which showed robust correspondence to the lithologies within the seismic volume. High seismic SRFs were often a good approximation for volumes containing a higher percentage of coarser-grained and distorted sediments, and vice versa. We believe that this is the first attempt at quantitative, integrated characterisation of mud-rich overburden sediment sequences using log and seismic data. Its application on modern seismic surveys can save days of processing/mapping time and can reduce exploration risk by basing decisions on seal texture and lithology probabilities.

2012/2013
I terremoti costituiscono un disastro naturale ricorrente su tutto il territorio italiano e per questo sono estremamente importanti interventi mirati e rapidi di protezione civile. La rapidità di questi interventi dipende dalla produzione di localizzazioni veloci e possibilmente in tempo reale degli eventi sismici. La precisione delle localizzazioni, inoltre, è necessaria per identificare le faglie sismogenetiche. Per questi due aspetti, è necessario un miglioramento dei sistemi di monitoraggio esistenti in modo da poter accrescere la qualità delle localizzazioni automatiche in tempo reale. Lo scopo di questo studio è la scrittura di una procedura che localizza accuratamente eventi sismici in tempo reale. La qualità delle localizzazioni è fortemente dipendente dalla corretta determinazione delle fasi P ed S. A volte è difficile riconoscere il corretto arrivo di una fase, poiché il segnale sismico può essere di difficile lettura per differenti motivi, come, ad esempio, la complessità del meccanismo della faglia generatrice e la presenza di rumore sia naturale che artificiale. Per questo motivo abbiamo studiato, analizzato e comparato differenti metodi per la rilevazione delle fasi e per la localizzazione degli eventi sismici. Gli algoritmi di rilevazione delle fasi che sono stati valutati sono lo Short Time Average su Long Time Average ratio (STA/LTA) e la funzione di Akaike Information Criterion (AIC). Il primo di questi è una tecnica comune usata per distinguere il segnale sismico dal rumore. E’ basato sul calcolo continuo di due valori medi dell’ampiezza assoluta di un segnale sismico in due finestre di tempo di differente lunghezza: media sull’intervallo breve (STA) e media sull’intervallo lungo (LTA). Il rapporto di queste due medie (STA/LTA) viene comparato ad un valore di soglia. Quando questo rapporto è maggiore della soglia, viene rilevata una fase nel segnale sismico analizzato. Il settaggio di questo sistema dipende dalla scelta dei parametri, questo prouce instabilità. La funzione di AIC è una metodologia sofisticata e precisa [Akaike and Hirotugu, 1974], basata sul classico metodo della massima verosimiglianza. La sua applicazione più comune consiste nella selezione tra pi` modelli: la stima della massima verosimiglianza dei parametri del modello da il minimo della funzione AIC. Questo metodo è strettamente correlato alla scelta della finestra di tempo nella quale applicare la funzione. Per questo motivo è necessaria una combinazione di più tecniche in modo da poter scegliere automaticamente la finestra corretta. In un segnale sismico il minimo della funzione AIC identifica l’arrivo delle onde P o delle onde S. Questa funzione è utilizzata nella procedura dell’AutoPicker [Turino et al., 2010]. Una volta identificate le fasi, è necessario elaborarle in modo da poter localizzare eventi sismici. In Antelope la procedura di localizzazione è chiamata orbassoc. Questa metodologia legge le fasi rilevate tramite il metodo STA/LTA e cerca di produrre una localizzazione dell’evento sulle tre possibili griglie: telesismica, regionale e locale. La soluzione, che produce tempi teorici di percorrenza per ogni stazione, che si accordano maggiormente con le osservazioni, viene considerata la migliore. Nell’AutoPicker l’algoritmo di localizzazione è Hypoellipse [Lahr, 1979], nel quale i tempi di percorrenza sono stimati utilizzando una struttura a strati piani paralleli e gli ipocentri sono calcolati utilizzando il metodo di Geiger [Geiger, 1912]. In questo lavoro abbiamo utilizzato metodologie per la localizzazione diverse da quelle assolute come Hypoellipse. L’HypoDD [Waldhauser and Ellsworth, 2000] è un algoritmo relativo, ovvero le localizzazioni vengono calcolate in riferimento alla localizzazione di un evento principale o dal sito di una stazione. Questo metodo può essere applicato solo nel caso in cui la distanza ipocentrale tra i due terremoti è piccola comparata alla distanza evento-stazione e alle eterogeneità laterali del campo delle velocità. In questi casi il percorso del raggio tra le due sorgenti e una stazione comune sono simili per gran parte del percorso del raggio. Per testare le prestazioni dell’AutoPicker, lo abbiamo applicato ad un database di 250 eventi registrati nell’area di contatto tra le Alpi e le Dinaridi nell’anno 2011 dalla rete C3ERN - the Central Eastern European Earthquake Reasearch Network [Dipartimento di Matematica e Geoscienze (DMG), Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), Agencija RS za okolje (ARSO) e Zentralanstalt fr Meteorologie und Geodynamik (ZAMG)]. L’algoritmo automatico proposto è risultato essere un utile strumento per l’assegnazione automatica degli arrivi delle onde P ed S. Questo risultato incoraggiante ci ha permesso di procedere nel confronto tra questa nuova metodologia e Antelope, utilizzato da noi quotidianamente in tempo reale per rilevare fasi e localizzare eventi. La complessità del contesto tettonico influenza il percorso dei raggi e conseguentemente la localizzazione degli eventi. In regioni dove sono presenti molte strutture sismogenetiche, una localizzazione precisa della sequenza sismica è essenziale, in modo da capire quale è la faglia generatrice. In questi casi l’uso di modelli 1-D potrebbe non essere sufficiente, mentre un modello 3-D potrebbe descrivere al meglio l’area interessata. La tomografia dei primi arrivi è una tecnica comune per ottenere un modello tridimensionale dalla localizzazione degli eventi. In questo studio abbiamo utilizzato una tomografia di eventi locali (Local Earthquake Tomography, LET) [Aki, 1982]. La tomografia dei primi arrivi e la localizzazione 3-D degli eventi sono state eseguite, rispettivamente, utilizzando il Computer Aided Tomography per modelli 3D (Cat3D) [Cat3D user manual, 2008] e il Non Linear Location (NonLinLoc) [Lomax et al., 2000] attraverso una procedura iterativa. Il Cat3D viene utilizzato solitamente in sismica attiva, mentre in questo studio è stato applicato ad un caso sismologico. La principale differenza tra la sismica attiva e la sismologia sono le incertezze nel sistema tomografico. Nella sismica attiva la localizzazione della sorgente è ben definita mentre nella sismologia è una variabile con incertezza elevata che si propaga nella stima del percorso del raggio e dei tempi di percorrenza. Per risolvere questo problema, abbiamo utilizzato una procedura iterativa composta dalla tomografia dei primi arrivi e dalla rilocalizzazione degli eventi con il modello 3-D risultante. Dopo il verificarsi della sequenza sismica emiliana nel Maggio-Giugno 2012, abbiamo deciso di analizzarla come interessante caso di studio. La sequenza sismica è iniziata il 20 Maggio (02:03:53 UTC), con un terremoto di Ml 5.9 [Scognamiglio et al., 2012]. Questa sequenza è composta da migliaia di eventi, sei dei quali con Ml maggiore di 5.0, tra cui un evento di magnitudo locale 5.8, il 29 Maggio (07:00:03 UTC). Su questi eventi abbiamo testato le prestazioni dell’AutoPicker e di Antelope. Per fare ciò abbiamo rilevato manualmente le fasi e localizzato alcuni degli eventi maggiori della sequenza sismica. Questi eventi sono caratterizzati da fasi P, ma in particolar modo fasi S, difficili da rilevare, probabilmente a causa del complesso meccanismo di faglia. Inoltre la complessità del sistema tettonico assieme all’incertezza della profondità focale rendono problematiche le localizzazioni degli eventi. La sequenza sismica emiliana ha interessato un’area di 50 km con andamento E-W localizzata nell’angolo sud della Pianura Padana, interessando il settore centrale dell’arco di Ferrara appartenente al sistema esterno della cintura degli Appennini Settentrionali. L’arco di Ferrara è composto da due sistemi: le pieghe di Ferrara nel nordest e la piega di Mirandola localizzata nella parte più interna a sudovest [Govoni et al., 2014]. Abbiamo elaborato gli arrivi P ed S in modo da poter localizzare la sequenza sismica utilizzando differenti modelli di velocità trovati in letteratura: Bragato et al. [2011], Ciaccio and Chiarabba [2002],Costa et al. [1992], Iside, Zollo et al. [1995], Malagnini et al. [2012], Massa [2012] e quattro modelli geologici proposti da Lavecchia et al. [in prep.] L’idea è di produrre un insieme di localizzazioni di eventi clusterizzati con residui minimi, in modo da poter capire quale è la faglia generatrice. Questo lavoro è stato svolto in collaborazione con l'Università di Chieti e il Dipartimento di Protezione Civile (DPC). Dalla distribuzione ipocentrale delle soluzioni, sembra che l'arco di Mirandola non sia coinvolto nella sequenza sismica, mentre i segmenti della parte interna e centrale del sistema di sovrascorrimento di Ferrara sembrano essere stati attivati dalle sequenze sismiche del 29 e del 20 Maggio, rispettivamente. La complessità dell'area interessata dalla sequenza sismica dell'Emilia, richiede il calcolo di modelli tridimensionali di velocità in modo da poter localizzare più precisamente gli eventi. Come già detto, abbiamo elaborato una procedura iterativa: tomografia dei primi arrivi e localizzazioni 3-D degli eventi, attraverso l'uso rispettivamente del Cat3D e del NonLinLoc, in collaborazione con l'OGS. La sequenza sismica copre solo una piccola parte della regione (30x30 km^2 di larghezza e 20 km di profondità), per questo l'area investigata si limiterà alla porzione superiore della crosta. Come modelli iniziali di velocità abbiamo scelto: Costa et al, 1992; Massa et al. 2013 e NewModel1 (LaVecchia et al., in prep., i quali avevano errori verticali inferiori al chilometro nello studio precedente. Il miglior modello iniziale sembra essere quello di Massa et al. (2013), il quale mostra valori di rms bassi rispetti alle altre soluzioni. I tre modelli tridimensionali di velocità per le onde P risultanti mostrano caratteristiche comuni: uno strato superficiale a bassa velocità e uno strato spesso (5-20 km in profondità) a 5.5km/s. I risultati tomografici per i modelli Vs presentano un comune strato superficiale a bassa velocità e uno strato caratterizzato da valori di velocità per le onde S di 3.0 km/s. Le tre serie di soluzioni, dei differenti modelli di velocità, sono comparabili all'interno dell'intervallo di errore, anche in termini di qualità. Le localizzazioni per la scossa principale del 20 maggio 2012 sono sparpagliate rispetto a quelle della seconda scossa principale del 29 maggio. Una possibile causa potrebbe essere l'installazione delle stazioni temporanee nel campo vicino della sequenza sismica dopo il 20 maggio 2012. Per l'evento del 29 maggio, infatti, si hanno molte più registrazioni che per il primo evento del 20 e tutte in campo vicino. Le localizzazioni degli eventi ottenute da modelli tomografici tridimensionali sono meno disperse di quelle ottenute con modelli unidimensionali, anche se le localizzazioni dei due eventi principali sono simili. In profondità le due serie di soluzioni non differiscono in modo significativo. Per migliorare la qualità della procedura di localizzazione nel nostro centro di raccolta dati, vorremo installare una procedura automatica sia rapida sia precisa. Per raggiungere questo risultato abbiamo comparato l'AutoPicker con Antelope sulla sequenza sismica dell'Emilia. Questo confronto è di fondamentale importanza per comprendere quale dei due algoritmi rileva fasi e/o localizza eventi in modo più preciso. Il nostro scopo, infatti, è quello di unire ed implementare queste due tecniche in modo da ottenere un miglior rilevatore di fasi e localizzatore. I risultati di questo confronto ci hanno portato a concludere che l'AutoPicker trova più fasi e con maggior precisione rispetto ad Antelope, sia per le fasi P che per le fasi S. Nonostante ciò il processo di associazione delle fasi in Antelope è in grado di correggere gli errori delle fasi e trovare la corretta localizzazione dell'evento. Questo ci ha suggerito di implementare l'algoritmo dell'AutoPicker nella procedura di Anteope, in modo tale che l' AutoPicker definisca gli arrivi P ed S e Antelope li associ e localizzi gli eventi. Con il miglioramento delle reti sismiche e la possibilità di raccogliere enormi quantitativi di dati, è necessario produrre enormi database, in modo da poter avere un rapido accesso ad essi e di poterli rielaborare in tempo reale o quasi reale. Per questi enormi database la rilevazione manuale delle fasi è un lavoro oneroso, che richiede tanto tempo. La possibilità di avere uno strumento che rilevi automaticamente fasi di ottima qualità, che producano risultati similari a quelli ottenuti dall'inversione tomografica utilizzando le fasi rilevate manualmente, è sicuramente conveniente ed utile. Per questa ragione abbiamo confrontato due differenti tomografie dei primi arrivi, prodotte con la stessa tecnica dell'analisi precedente, che differiscono solo per i dati di partenza: la prima è stata ottenuta dalle fasi rilevate manualmente, la seconda dalle fasi rilevate automaticamente con l'AutoPicker per la sequenza sismica dell'Emilia. I risultati ottenuti indicano un incremento del valore medio dell' rms sia nelle localizzazioni sia nella tomografia per le fasi automatiche. Nonostante questo i modelli tridimensionali ottenuti ( Vp, Vs and Vp/Vs) sono comparabili. Pertanto sembra che gli errori nelle localizzazioni non influenzino i risultati tomografici ma inficino la precisione del sistema tomografico stesso. Quindi per database contenenti enormi quantità di dati è possibile utilizzare le fasi automatiche come dati di partenza, ottenendo risultati comparabili a quelli ottenuti con le fasi manuali.
Earthquakes constitute a recurring natural disaster all over the Italian territory, and therefore civil defence focused interventions are extremely important. The rapidity of such interventions strongly depend on the production of fast and possibly real-time locations of the seismic events. The precise location of events is also needed to identify seismogenic faults. For these two aspects, an upgrade of the existing monitoring systems is fundamental to improve the automatic locations quality in a quasi real-time mode. The main purpose of this study is the production of a routine that will accurately locate seismic event in real-time. The quality of the locations strongly depends on the correct determination of the P- and S- phases. Sometimes it is hard to recognize the correct onset of a phase, since the signal can be blurred by various causes, such as, e.g., the complexity of the generating fault mechanism and the presence of natural or man-made noise. For this reason we have studied, analyzed and compared different phase picking and location methods. The picking algorithms that were evaluated are the Short Time Average over Long Time Average ratio (STA/LTA) and the Akaike Information Criterion (AIC) function. The first one is a common technique used to distinguish the seismic signal from noise. It is based on the continuous calculation of the average values of the absolute amplitude of a seismic signal in two moving-time windows with different lengths: the short-time average and the long-time average. The STA/LTA ratio is compared with a threshold value. When the ratio is larger than this threshold, the onset of a seismic signal is detected. The main disadvantage of this method is its instability, due to the parameters choice: a too long STA window could cause the non-detection of local events, whereas a too short STA window could cause the detection of man-made seismic noise. A high STA/LTA threshold records less events than the ones those have occurred, but false triggers are eliminated. If this value is chosen to be lower, more events will be detected, but more frequent false triggers could be recorded. This algorithm is part of the Antelope (BRRT, Boulder) detection procedure, used in this study. The AIC function is a precise and sophisticated methodology, being a revision of the classical maximum likelihood estimation procedure (Akaike, 1974). The AIC function is designed for statistical identification of model characteristics. Its most classical application consists in the selection of the best among several competing models; the maximum likelihood estimate of the model parameters gives the minimum of AIC function. It is strictly correlated to the correct choice of the time window in which apply the function, so it is necessary combined with other techniques, in order to automatically choose a correct window. This dependence on other methods, makes the application of the AIC function to detect phases, a complex methodology, which can be affected by errors in the parameter choices. The AIC function is used in the AutoPicker procedure (Turino et al., 2012). In a seismic signal the minimum of the AIC function identifies the P- or S- onset. In this automatic phase picker the time window in which to apply the function, in the case of P phases, is chosen by a combination of a band-pass filter and an envelope time function, used as “energy” detector to select the event in the waveform; for the S phases, the selection of the window is guided by a preliminary location of the P- phases. Once the P- and S- phases are identified, it is necessary to elaborate them in order to locate the seismic event. In Antelope the location procedure is called orbassoc. This methodology reads the pickings, determined through the use of the STA/LTA technique, and tries to produce an event location over three possible grids: teleseismic, regional and local. The solution that produces the minimum travel time residuals set (differences between synthetic travel times and observed travel times) is considered as the best one. In the AutoPicker the location algorithm is Hypoellipse (Lahr, 1979), in which the travel-times are estimated from a horizontally-layered velocity-structure and the hypocenter is calculated using Geiger's method (Geiger, 1912) to minimize the root mean square (rms) of the travel time residuals. In order to improve the location quality we have used in this work various location methodologies with respect to the absolute ones, such as Hypoellipse. The HypoDD (Waldhauser et al., 2000) is a relative algorithm, the locations depend either on the location of a master event or on a station site. This method can be applied only in the case when the hypocentral separation between two earthquakes is small compared to the event-station distance and the scale length of the velocity heterogeneities. In such cases the ray paths between the source region and a common station are similar along almost the entire ray path. In order to test the performances of the AutoPicker, we have applied it to a database of 250 events recorded in the year 2011 by the C3ERN - the Central Eastern European Earthquake Reasearch Network [Department of Mathematics and Geosciences (DMG), Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), Agencija RS za okolje (ARSO) and Zentralanstalt für Meteorologie und Geodynamik (ZAMG)] – at the Alps-Dinarides contact. The proposed automatic picker appears to be a useful tool for assigning automatically onset P and S times to detected seismic signals for the purpose of rapid hypocenter calculations. These encouraging results have allowed us to proceed comparing this new picking methodology to another one, tested and used daily and in real-time by us to detect and locate events, the Antelope software. The complexity of the tectonic environment influences ray tracing and consequently the event locations. In regions where many seismogenic structures are present, a precise location of a seismic sequence is essential, in order to understand which fault is the generating one. In such cases the use of a 1-D velocity model might not be sufficient, so a 3-D velocity model is a better solution to describe the studied area. The travel-time tomography is a common technique to obtain a 3-D velocity model, from event locations. In this study we have chosen a local earthquake tomography (LET) (Aki, 1982). The travel time tomography and the 3-D event location are performed, respectively, using the Computer Aided Tomography for 3D models (Cat3D) software (Cat3D manual, 2008) and the Non Linear Location (NonLinLoc) software (Lomax et al., 2000) through an iterative procedure. The Cat3D is basically used in active seismics, but in this study it is applied to a seismological case. The main difference between active seismics and seismology are the unknowns in the tomographic system. In seismology the source location is an unknown parameter with a high uncertainty, while in active seismics the source locations are well defined. In this study, the introduction of the source location in the tomographic system, introduces uncertainties in obth the ray tracing and travel-times estimation. In order to solve this uncertainty, we used an iterative procedure composed by the application of tomography and the event location in resulting 3-D velocity model. After the occurrence of the Emilia seismic sequence in May-June 2012, we have decided to investigate it as an interesting study case. The sequence started on May 20 (02:03:53 UTC), with a ML 5.9 earthquake, preceded by a M_L 4.1 foreshock, three hours earlier (Scognamiglio et al., 2012). Theaftershock sequence comprised thousands of earthquakes, six of them with M_L ≥ 5.0. Among these, a M_L 5.8 earthquake, on May 29 (07:00:03 UTC), caused probably more damages than the first shock. Through the study of this seismic sequence we have tested the performances of the automatic picking algorithms. In order to do that, we have manually picked and located some of the major events of this seismic sequence. These events are characterized by P- and especially S-phases, which are really difficult to detect, probably because the fault system of the Emilia earthquake area is complex. Moreover, the complexity of the tectonic environment along with the focal depth uncertainty make the event locations problematic, because it is not always easy to assess which fault has moved. The Emilia sequence occurred in the central, roughly E-W trending, sector of the Ferrara arc belonging to the external fold-and-thrust system of the Northern Apennines belt. The Ferrara arc is structured into two major fold-and-thrust systems: the Ferrara system in the northeast and the Mirandola system located in a more internal position to the southwest (Govoni et al., 2014). We have processed the P- and S- onsets in order to locate the seismic sequence using different velocity models found in literature: Bragato et al. (2011), Ciaccio et al. (2002), Costa et al. (1992), “Iside”, Zollo et al. (1995), Malagnini et al. (2012), Massa (Rapporto DPC-INGV S1-2013) and four geological models proposed by Lavecchia et al. (in prep). The idea is to produce a set of clustered event locations with the lowest residuals, in order to understand which is the generating fault in the complex system of faults. This work is being performed in collaboration with Università di Chieti and Department of Civil Defence (DPC). From the hypocentral distribution, it seems that the Mirandola thrust was not involved during the Emilia sequence, whereas the internal and middle segments of the Ferrara thrust systems were activated by 29 and 20 May seismic sequences, respectively. The complexity of the seismic sequence area in Emilia requires the calculation of a tridimensional velocity model in order to locate more precisely the events. As already said, we elaborated an iterative procedure: travel-time tomography and 3-D event locations, through the use of the Cat3D and NonLinLoc softwares, in collaboration with OGS. This is done to minimize the uncertainties introduced in the tomographic system by the unknown source locations. Since the seismic sequence covers only a small part of this region (about 30x30km^2 wide and 0-20 km deep), the investigated area will be limited to its upper crustal part. As initial velocity models, we have chosen those ones: Costa et al, 1992; Massa et al. 2013 and NewModel1 (LaVecchia et al., in prep.) that have vertical errors lower than one km. The best velocity model is the one, obtained using as initial model the Massa et al. (2013), which shows rms values lower than the others. The three resulting 3-D Vp velocity models shows similar characteristcs: a surface layer (0 – 5 km) of low Vp velocity, about 1,8 km/s, and a thick layer (5 – 20 km) of 5.5 km/s. The tomographic results for Vs velocity model present a common shallow layer (0 - 3 km) of low velocity (about 1 km/s) and a thick layer (3 - 13 km) characterized by a Vs velocity value of about 3.0 km/s. The three set of solutions, from the different velocity models, are comparable in the errors range. The locations for the main-shock of the 20th of May, 2012 are more scattered respect the solutions for the 29th's. A possible reason could be the installations of temporary stations in the near field of the sequence after the 20th of May, 2012. For the 29th event, in fact, we have more waveforms than for the previous main-shock, and all of them in the near field. We calculated the rms for each event in order to discriminate a velocity model with respect to another from the quality of the locations. We obtained three similar rms values trends, so we were not able to choose a best velocity model. The events locations from 3-D tomographic models are less scattered than those one computed from the 1-D ones; otherwise the locations of the two main-shock events seem to be quite similar. In depth the two set of solutions do not differ in a significative way. To improve the quality of the location procedure in our datacenter, we would like to install a precise and rapid automatic procedure. Therefore, we have compared the AutoPicker method with a more tested and solid one, the Antelope picking method, on the Emilia seismic sequence of data, using as reference pickings and locations the manual ones. This comparison is of fundamental importance which one of the two algorithms better detects phases and/or locates events. Our aim is, in fact, to merge and implement these two techniques to obtain a better detector and locator. AutoPicker finds more and preciser phases than Antelope both P- and mainly S-phases. Despite that the associator process in Antelope, is able to correctly associate the detections and to find the correct location. The obtained results suggest us to implement the AutoPicker algorithm in the Antelope procedure in order to use the AutoPicker to define P- and S-onset and Antelope to associate them and locate the events. With the improvement of seismic networks and the possibility to store huge amounts of data, it is necessary to produce big databases, in order to have a rapid access to the data and to re-elaborate them in real time o quasi real time mode. For big databases, the manual picking is an onerous work, requiring a lot of time. The possibility to have a good-quality automatic tool for phase recognition and picking, which produces similar results to those obtained from the tomographic inversion by using manual phases picking, is certainly convenient and useful. For this reason, we have compared two different travel time tomographic inversions made with the same technique of the previous analysis, differing only in the input phase files: the first one obtained from manual pickings, the second one from the automatic AutoPicker pickings of the Emilia sequence. The obtained results indicate an increase of the average rms both on the locations and on the tomography. Despite that, the tridimensional velocity models (Vp, Vs and Vp/Vs) are comparable, therefore, it seems that the location errors do not influence the tomographic results but the precision of the tomographic system. So for a large database it is possible to use automatic phases as input in a travel-time tomography, obtaining similar results as those obtained using manually picked phases.
XXVI Ciclo
1985

In seismology, an important goal is to attain a better understanding of the earthquake process. In this study of the physics of aftershock generation, I couple statistical analysis with modelling of physical processes in the postseismic period. I present a theoretical formulation for the distribution of interevent times for aftershock sequences obeying the empirically well established Omori law. As opposed to claims by other authors, this work demonstrates that the duration of the time interval between two successive earthquakes cannot be used to identify whether or not they belong to the same aftershock sequence or occur as a result of the same underlying process. This implies that a proper understanding of earthquake interevent time distributions is necessary before conclusions regarding the physics of the earthquake process are drawn. In a discussion of self-organised criticality (SOC) in relation to empirical laws in seismology, I find that Omori's law for aftershocks cannot be used as evidence for the theory of SOC. Instead, I consider that the occurrence of aftershocks in accordance with Omori's law is a result of a physical process that can be modelled and understood. I analyse characteristic features in the spatiotemporal distribution of aftershocks in the south Iceland seismic zone, following the two M6.5 June 2000 earthquakes and a M4.5 earthquake in September, 1999. These features include an initially constant aftershock rate, whose duration is larger following a larger main shock, and a subsequent power law decay that is interrupted by distinct and temporary deviations in terms of rate increases and decreases. Based on pore pressure diffusion modelling, I interpret these features in terms of main shock initiated diffusion processes. I conclude that thorough data analysis and physics-based modelling are essential components in attempts to improve our understanding of processes governing the occurrence of earthquakes.

The profound cultural transformation that has taken place in Italian seismic studies in the last ten years is distinguished by the growing interest in the problem of assessing the effects of earthquakes linked to local conditions, and in the related issue of a precise definition of the properties of the soil in the sphere of the dynamic and cyclical stresses induced by seismic actions. Despite the profound awareness of the extent to which the nature of the soil contributes to the destructive effects of earthquakes, we are still a long way from the possibility of a realistic forecast of the seismic behaviour of the Italian soils. This is because the identification of the dynamic properties calls for experimental equipment that is technologically complex and costly as well as lengthy observation and qualified personnel. The rare experimental data that have been acquired to date hence represent a fundamental element for scientific reflection. This book has been conceived with a view to setting at the disposal of a broader public the results of the tests conducted on site and in the laboratory on the soil of certain significant seismic areas using the dynamic-type apparatus of the Geotechnical Laboratory of the Department of Civil and Environmental Engineering (DICeA) of the University of Florence. It presents a selection of the works of the Geotechnical section of the DICeA that have been published in various specialist international and national ambits. These studies were largely launched following the seismic sequence in Umbria and the Marches, in collaboration with several Regional Authorities and Research Institutes for the reduction of the seismic risk in Italy (GNDT, IRRS, INGV). In addition to the experimental techniques and the results obtained, the models and the geotechnical procedures adopted for assessing the effects of site and soil instability in certain specific deposits of the Italian territory are also expounded.

The Examination Guide for Seismic Design of NPP was revised in 2006 in Japan. In response to the revised guide, utilities are required to establish the seismic design acceleration of the NPP site and evaluate the residual risk of individual NPP for earthquakes exceeding the seismic design acceleration. JNES is developing seismic PSA models of typical NPPs to support the regulatory review of utility’s residual risk evaluation report. Trial analysis of seismic PSA is performed for a typical BWR4 plant and a typical BWR5 plant. Dominant accident sequences and dominant initiating events are obtained, and sensitivity analysis is performed to evaluate the influence of analytical conditions on the core damage frequency (CDF) such as LOCA model and system mitigation effect. Analysis result shows that the CDF profile changes largely depending on the seismic intensity of the site.

Abstract Currently, the sequence-stratigraphic section dismemberment is only being implemented in Ukraine, so this article is highly relevant. The authors created geological 3D model of Komyshnianske gas condensate field based on sequence-stratigraphic section dismemberment for the first time at this area. This approach is effective for the following conditions:-insufficient field geological study;-thickness of productive horizons does not reach the seismic resolution boundaries;-no significant difference in impedance values on reflection horizons. The selected technique includes the following stages:-field geological study, facies analysis (integration of well geophysical complexes, cores);-deduction and correlation of sequence boundaries;-construction of discrete log, which corresponds to specific sequences distribution;-conducting seismic interpretation of the 3D seismic survey study of research area;-construction of a structural framework with the involvement of correlated sequences boundaries;-comparison of volume seismic attributes with selected sequences distribution. A geological 3D model of Komyshnianske gas condensate field was created based on sequence-stratigraphic principles. During the research, a geological structure of field was analyzed, the separated conditions of sedimentation (sequences) were deducted and interpreted. During the seismic interpretation of 3D seismic survey of study area, local features of wave field were identified, their reflection in the core material was found and linked to the concept of changing sedimentation conditions. With a general understanding of the material transportation and accommodation direction, used method allows to qualitatively outline the distribution boundaries of sedimentation certain conditions and predict their development outside the study area. Construction of facies discrete log and their distribution in the seismic field allows grouping thin bed layers of collectors to reach the seismic resolution and use them to predict the distribution of facies associated with changes in the rocks reservoir properties (tracking beach facies of deltas/avandeltas, sloping sediments, etc.). The constructed model could be used as a trend for reservoir distribution at the stage of construction of static geological model. Involvement of sequence-stratigraphy technique is new approach to sedimentation conditions study within Dnipro-Donetsk depression (DDD) areas. The paper shows that provided methodology gives:-improved geological understanding of field through sedimentation analysis and facies logging;-trends for reservoir properties distribution with the involvement of construction facies volumes;-proposals for further field E&D. The general provisions under conditions of geological materials sufficient base can be applied to other DDD areas, especially in pre-border zones. Involvement of sequence-stratigraphy technique is new approach for sedimentation conditions study within Dnipro-Donetsk depression (DDD) area. On the example of Komyshnianske gas condensate field, the article shows that provided methodology gives:-improved geological understanding of field through sedimentation analysis and facies logging;-trends for reservoir properties propagation with the involvement of seismic volume studies;-propositions for further field Exploration & Development.

Abstract The Shuaiba Formation, one of the primary reservoirs of Early Cretaceous Petroleum System, has been an important exploration target in onshore Abu Dhabi due to its excellent reservoir quality specifically along the platform margin. Initially the Bab Basin carbonate development was slow but increased during lowstand sequences of Upper Shuaiba which is also known as Shuaiba Sequence 5 (Strohmenger et al., 2010). The Upper Shuaiba is distinguished from Lower Shuaiba by the presence of clay, high frequency and low amplitude progradational sequences. This study is going to describe the nature of the carbonate development within these Upper Shuaiba sequences in western Abu Dhabi. Newly acquired 3D seismic data, existing well data and regional information have been utilized for seismic interpretation and litho-facies analysis to characterize Shuaiba Sequence 5. These interpretations were then linked to the depositional processes which generated the geometries and distribution of facies. Based on well correlations within the study area, the Bab shale is roughly 100ft near the Shuaiba platform. It forms a wedge on the slope of the platform and gradually thins out to ~17ft towards the north. The deposition of the shale is attributed to influx of terrigenous sediments during the lowstand, which were later distributed by longshore currents as inferred from seismic attribute maps. The occurrence of carbonate above the Bab shale has been related to the cessation of siliciclastic input, which created a suitable environment for a carbonate factory. Shallow water depth and frequent sea level fluctuations created several thin clinoform sequences. These fourth order sequences are observed to have an average thickness of ~20ms and are often restricted within two seismic reflectors. The orientation of the clinoforms is NW-SE. These are categorized into three sets as reported by previous authors (Pierson et al., 2010 & Whitcomb et al., 2021). The clinoforms have higher amplitude in the top set, which gets dimmer in the bottomset. Lithofacies from core data show the presence of thin beds of floatstone to packstone at the topset, which could form potential reservoir subject to better permeability development. The overlying Nahr Umr shale is the regional seal. The clinoform sets are located over a NE-SW oriented structural trend and may form subtle traps due to updip facies change within the clinoforms. Similar type of strati-structural trapping mechanism could be found along the strike of these clinoform sequences and may become potential prospects for hydrocarbon exploration in western Abu Dhabi.

Abstract Depositional sequence unbundling was done to understand the depositional environment from six wells through the analysis of gamma-ray logs using shale volume, and a 3D post-stack seismic. Identified hydrocarbon reservoir formations were laterally tracked to assess horizon continuity and spatial draping of the units. Horizon surfaces were built post-correlation to examine the bounded zones and reconcile sequences. Gamma-ray log motifs for the deposits indicate the presence of progradational, retrogradational, and aggradational sequence patterns that typifies prevalent energies at the time deposition, characteristic of deltaic environment. On the seismic sections, aggradational reflectors dominate over the other two. Although current well placements do not conform to structural attitude, petrophysical analysis done over the horizons indicate a significant increase in porosity and hydrocarbon saturation basin-ward (South-west), in the direction of the frontier prospect to site more wells.

In south-central Ontario, tunnel channels are primary targets for groundwater exploration due to their potential to contain confined, water-bearing, coarse-grained sediment fills. Despite extensive hydrogeologic and geologic exploration within these features, a comprehensive depositional model that illustrates the spatial distribution of coarse- and fine- grained sediment in tunnel-channel complexes is absent. Work in the Zephr area, north of ORM, presents new subsurface data to improve understanding of this geologic setting and to add to geologic models of these channel systems. Findings result from combined geology, sedimentology, geophysics (seismic profiling) and sediment drilling (mud rotary and continuous core) to better our understanding the shallow channel setting north of ORM, including: 1) spatial distribution of coarse- and fine-grained sediments in tunnel-channels; 2) the architecture of tunnel-channel sequences in confluence zones. Preferred aquifer targets aquifer units in the Zephyr area are identified in areas of channel confluence and channel bends. Channel aquifers are confined by 3.9 to 28.5 m thick deposits of rhythmically bedded silt and clay.

The Geological Survey of Canada conducted a broad regional study of the Magdalen Basin in the Gulf of St. Lawrence, as part of the Marine Conservation Targets initiative. MCT is a national initiative to protect more of Canada's offshore areas, and resource assessment and related regional mapping are part of the review process. This study assembled a large seismic and geologic database that allowed new regional mapping of several key horizons in this basin. Digital seismic data was donated by industry, and reprocessing undertaken both in-house and with contractors. Wells were correlated and tops from literature were used to indentify regional reflection packages. Regionally consistent two-way time interpretations add to confidence. Depth conversion used regional time-depth functions from literature, which were developed from refraction data, with a residual correction for the water column. Nine regional depth maps and eight isopach maps were produced, including Pre-Horton Basement, Horton Group Isopach, Base Windsor Group, Top Salt, Top Bradelle Formation, Bradelle / Cumberland Isopach, and Top Cable Head Formation. These maps illustrate that the Pre-Horton basement is about 15 km deep in the centre of the basin. Two main trends are visible in the Horton Grabens, which may relate to basin formation, and no significant reactivation of deeper Appalachian structure is observed. In the basin centre, the more robust Base Windsor Unconformity horizon reaches about 12 km deep, and a key reservoir and source sequence in the Bradelle Formation reaches 7 km. These maps are useful for considering regional stratigraphy. The new mapping also constrained basin models and became the input for our Qualitative Petroleum Potential map. Basin modelling reveals scenarios where oil may be preserved. The petroleum potential of the region is highest north of Îles de la Madeleine and southeast of Îles de la Madeleine and northwest of Cape Breton.