ABSTRACT El norte de Venezuela está ubicada en la zona de interacción de las placas del Caribe y ... more ABSTRACT El norte de Venezuela está ubicada en la zona de interacción de las placas del Caribe y de Sudamérica, lo que ha generado una compleja zona de interacción a nivel de las litosferas. Durante los estudios realizados en el marco de los proyecto GEODINOS y BOLÍVAR desde el año 2003 se determinaron las principales estructuras del norte de Venezuela, tanto a nivel del manto como en la corteza. Los estudios sismológicos y gravimétricos se complementaron con estudios geológicos destinados a conocer la historia de deformación de las unidades metamórficas, así como las cuencas cuaternarias asociadas a los principales sistemas de deformación.
The perfectly matched layer (PML) boundary condition has been widely used as a very effective abs... more The perfectly matched layer (PML) boundary condition has been widely used as a very effective absorbing boundary condition for seismic wavefield simulations. Convolutional PML (CPML) achieved by using a complex frequency-shifted stretch function was the latest development to further improve PML’s absorption performance for near-grazing angle incident waves as well as for low-frequency incident waves. However, the mathematical theory of the PML method is derived from the first-order equation, all PML implementations of second-order equations are to introduce auxiliary equations or variables to rewrite original PML equations, which will complicate the implementation. In this article, we propose a simple and efficient CPML implementation method for the second-order elastic wave equation, which directly simulates the second-order CPML equation. The main advantage of this method is that there is no need to introduce auxiliary variables or auxiliary equations to convert the second-order PML equation from the complex coordinate space to the real axis. Comparedwith the conventional CPMLmethod for the secondorder elastic wave equation, it introduces only eight convolution variables. We demonstrate the validity and absorption performance through extensive numerical experiments. ARTICLE HISTORY Received 20 April 2021 Accepted 4 October 2021
The geology of China has been found to be highly diverse, consisting of various tectonic zones fr... more The geology of China has been found to be highly diverse, consisting of various tectonic zones from the ancient Archean Sino-Korean and Yangtze cratons to the young and active Tibetan Plateau formed by the Cenozoic India-Eurasia collision. China is also a country with high levels of seismic activity, and has a history of strong earthquakes that caused great loss in both life and property. Therefore, knowledge of the anisotropic structure of the crust beneath China has great importance in understanding crustal and lithospheric deformation, as well as locating earthquake hypocenters and investigating the mechanism of strong earthquakes in China. We analyzed a large amount of high-quality broadband teleseismic receiver function data recorded by a total of 36 Chinese National Digital Seismic Network stations between September of 2000 and December of 2010. At each station, we collected more than 500 receiver functions, which showed a very good coverage in back azimuth that is required to...
ABSTRACT The understanding of the depth dependency of the inner core attenuation is important to ... more ABSTRACT The understanding of the depth dependency of the inner core attenuation is important to constrain the physical mechanism and state of the inner core but it is still controversial. In Iritani et al. [2010, GRL], we employed a waveform inversion method based on simulated annealing (SA) that enables to analyze complicated waveforms contaminated by phase overlaps, and applied it to Japanese Hi-net data. The attenuation model we obtained beneath the northeastern Pacific shows a gradual increase of the attenuation from ICB to 200 - 250 km depth and a decrease from this depth range and its possible relation to the growing process of the inner core was suggested (cf. Monnereau et al., 2010, Science). The purpose of this study is to investigate whether the attenuation structure obtained by analyzing Japanese data is just a local feature or more a general feature in the western hemisphere of the inner core. We apply the same method as Iritani et al. [2010] to the NECESSArray data. NECESSArray is a large temporary broadband seismic array installed in Northeastern China (from Sep. 2009 to August 2011). Core phases observed by this array for earthquakes occurred in South America region pass in the inner core beneath central Canada and together with the Japanese data coverage, a wide region of the western hemisphere can be sampled. We have so far analyzed triplicated core phase data for 6 events occurred in South America. Measured attenuation parameters show a gradual increase with distance and that is consistent with the result of Iritani et al. [2010]. It suggests that a similar structure extends widely beneath the North American continent and that the obtained attenuation structure may be representative structure of the western hemisphere.
ABSTRACT El norte de Venezuela está ubicada en la zona de interacción de las placas del Caribe y ... more ABSTRACT El norte de Venezuela está ubicada en la zona de interacción de las placas del Caribe y de Sudamérica, lo que ha generado una compleja zona de interacción a nivel de las litosferas. Durante los estudios realizados en el marco de los proyecto GEODINOS y BOLÍVAR desde el año 2003 se determinaron las principales estructuras del norte de Venezuela, tanto a nivel del manto como en la corteza. Los estudios sismológicos y gravimétricos se complementaron con estudios geológicos destinados a conocer la historia de deformación de las unidades metamórficas, así como las cuencas cuaternarias asociadas a los principales sistemas de deformación.
The perfectly matched layer (PML) boundary condition has been widely used as a very effective abs... more The perfectly matched layer (PML) boundary condition has been widely used as a very effective absorbing boundary condition for seismic wavefield simulations. Convolutional PML (CPML) achieved by using a complex frequency-shifted stretch function was the latest development to further improve PML’s absorption performance for near-grazing angle incident waves as well as for low-frequency incident waves. However, the mathematical theory of the PML method is derived from the first-order equation, all PML implementations of second-order equations are to introduce auxiliary equations or variables to rewrite original PML equations, which will complicate the implementation. In this article, we propose a simple and efficient CPML implementation method for the second-order elastic wave equation, which directly simulates the second-order CPML equation. The main advantage of this method is that there is no need to introduce auxiliary variables or auxiliary equations to convert the second-order PML equation from the complex coordinate space to the real axis. Comparedwith the conventional CPMLmethod for the secondorder elastic wave equation, it introduces only eight convolution variables. We demonstrate the validity and absorption performance through extensive numerical experiments. ARTICLE HISTORY Received 20 April 2021 Accepted 4 October 2021
The geology of China has been found to be highly diverse, consisting of various tectonic zones fr... more The geology of China has been found to be highly diverse, consisting of various tectonic zones from the ancient Archean Sino-Korean and Yangtze cratons to the young and active Tibetan Plateau formed by the Cenozoic India-Eurasia collision. China is also a country with high levels of seismic activity, and has a history of strong earthquakes that caused great loss in both life and property. Therefore, knowledge of the anisotropic structure of the crust beneath China has great importance in understanding crustal and lithospheric deformation, as well as locating earthquake hypocenters and investigating the mechanism of strong earthquakes in China. We analyzed a large amount of high-quality broadband teleseismic receiver function data recorded by a total of 36 Chinese National Digital Seismic Network stations between September of 2000 and December of 2010. At each station, we collected more than 500 receiver functions, which showed a very good coverage in back azimuth that is required to...
ABSTRACT The understanding of the depth dependency of the inner core attenuation is important to ... more ABSTRACT The understanding of the depth dependency of the inner core attenuation is important to constrain the physical mechanism and state of the inner core but it is still controversial. In Iritani et al. [2010, GRL], we employed a waveform inversion method based on simulated annealing (SA) that enables to analyze complicated waveforms contaminated by phase overlaps, and applied it to Japanese Hi-net data. The attenuation model we obtained beneath the northeastern Pacific shows a gradual increase of the attenuation from ICB to 200 - 250 km depth and a decrease from this depth range and its possible relation to the growing process of the inner core was suggested (cf. Monnereau et al., 2010, Science). The purpose of this study is to investigate whether the attenuation structure obtained by analyzing Japanese data is just a local feature or more a general feature in the western hemisphere of the inner core. We apply the same method as Iritani et al. [2010] to the NECESSArray data. NECESSArray is a large temporary broadband seismic array installed in Northeastern China (from Sep. 2009 to August 2011). Core phases observed by this array for earthquakes occurred in South America region pass in the inner core beneath central Canada and together with the Japanese data coverage, a wide region of the western hemisphere can be sampled. We have so far analyzed triplicated core phase data for 6 events occurred in South America. Measured attenuation parameters show a gradual increase with distance and that is consistent with the result of Iritani et al. [2010]. It suggests that a similar structure extends widely beneath the North American continent and that the obtained attenuation structure may be representative structure of the western hemisphere.
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