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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy (S) - IASPEI - International Association of Seismology and Physics of the Earth's Interior JSS014 Poster presentation 2307 Gravity anomalies and lithosperic structure across the co-seismic rupture of great Sumatra-Andaman earthquake Dr. Virendra Mani Tiwari GRAVITY National Geophysical Research Institute IASPEI V. M. Tiwari, K. Arora, B. Singh The 26th December 2004 Sumatra-Andaman earthquake of Mw=9.3 ruptured a 1300-km-long portion of plate boundary, where the oceanic Indo-Australian plate underthrusts the Burmese plate. Rupture parameters derived from geodetic model suggest segmented asperity. Coincidentally, this segmentation has a visual correlation with gravity anomalies. Therefore, we have analysed gravity anomalies to define lithospheric structure and geometry of subduction zone along a few traverses to understand how the variations in the coseismic slip of the Sumatra earthquake correspond to the variations in the lithospheric/crustal structure Keywords: sumatra andaman, gravity anomalies, lithospheric structure
IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy (S) - IASPEI - International Association of Seismology and Physics of the Earth's Interior JSS014 Poster presentation 2308 Paleostresses and recent tectonic activity of the Palomares-Carboneras strike-slip faults (Eastern Betic Cordilleras, SE Spain) Dr. Patricia Ruano Dept. Geodinmica i Geofisica. U Barcelona Researcher Jess Galindo-Zaldvar, Carlos Marn-Lechado Palomares NNE-SSW and Carboneras NE-SW oriented strike-slip faults separate the southeastern end of the Betic Cordilleras and the Alboran Sea- South Balearic basin thin continental crust. These faults belong to the Trans Alboran shear zone- that has been considered a deep fracture zone with related volcanism, crossing the Betic-Rif Cordilleras. The age of their activity has been broadly discussed on the literature, and most of the authors suggest evidences of a minimum slip up to several tens of kilometers since the Miocene, with sinistral strike-slip regime and extensional episodes. Although these faults have not a clear present-day associated seismicity, there are local evidences of their recent activity. However, up to date, there is no detailed discussion or analysis of the interaction between these two oblique oriented major faults, with very straight cartographic traces.They should undergone a large geometrical interaction that is not evidenced at their intersection. This contribution aims to discuss the relationships between the activity of Palomares and Carboneras major faults, taking into account new field geological data on brittle deformation near faults zones. The palaeostresses determined from the analysis of microfaults and joints evidence NE-SW extension during the Tortonian, related to the development of normal faults, and local NW-SE compression. During the Messinian, compression rotates clockwise to the NNE-SSW and favors the sinistral strike-slip of the Carboneras Fault Zone, the dextral strike-slip of minor NW-SE oriented faults and the development of large folds such as the Sierra Alhamilla antiform. During the Pliocene, an anticlockwise rotation of stresses produces NNW-SSE oriented compression, which contributes to fold development. These stresses favoured the sinistral activity of the Palomares fault, with regard to Carboneras Fault.Finally, during the Quaternary an ENE-WSW extensional setting and NNW-SSW to NW-SE compression predominate, and secondary NW-SE normal faults develop. Local sinistral regime on Carboneras Fault may be consequence of the accommodation of the displacement of NW-SE normal faults, making it act as a transfer fault. In addition, local NW-SE extension has been also determined. NW-SE compression favoured the sinistral strike-slip activity of Palomares Fault regarding the orthogonally oriented Carboneras Fault. The geological field and geomorphological data also confirm the most intense recent activity of Palomares Fault zone, determining the orientation of the coast line. This fault zone, extending to the north along the Arteal Fault, probably displaces Carboneras Fault which shows only local evidences of recent sediment deformation and physiographic feature displacements, typical of a relatively moderate activity. Keywords: paleostress, palomares fault, recent tectonics
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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy<br />
(S) - <strong>IASPEI</strong> - International Association of Seismology and Physics of the Earth's<br />
Interior<br />
JSS014 Poster presentation 2307<br />
Gravity anomalies and lithosperic structure across the co-seismic rupture<br />
of great Sumatra-Andaman earthquake<br />
Dr. Virendra Mani Tiwari<br />
GRAVITY National Geophysical Research Institute <strong>IASPEI</strong><br />
V. M. Tiwari, K. Arora, B. Singh<br />
The 26th December 2004 Sumatra-Andaman earthquake of Mw=9.3 ruptured a 1300-km-long portion of<br />
plate boundary, where the oceanic Indo-Australian plate underthrusts the Burmese plate. Rupture<br />
parameters derived from geodetic model suggest segmented asperity. Coincidentally, this segmentation<br />
has a visual correlation with gravity anomalies. Therefore, we have analysed gravity anomalies to define<br />
lithospheric structure and geometry of subduction zone along a few traverses to understand how the<br />
variations in the coseismic slip of the Sumatra earthquake correspond to the variations in the<br />
lithospheric/crustal structure<br />
Keywords: sumatra andaman, gravity anomalies, lithospheric structure