Fault plane structure of the 1995 Antofagasta Earthquake (Chile) derived from local seismological parameters

Fault planes of large earthquakes incorporate inhomogeneous structures. This can be observed in teleseismic studies through the spatial distribution of slip and seismic moment release caused by the mainshock. Both parameters are often concentrated on patches on the fault plane with much higher values for slip and moment release than their adjacent areas. These patches are called asperities which obviously have a strong influence on the mainshock rupture propagation. Condition and properties of structures in the fault plane area, which are responsible for the evolution of such asperities or their significance on damage distributions of future earthquakes, are still not well understood and subject to recent geo-scientific studies. In the presented thesis asperity structures are identified on the fault plane of the Mw=8.0 Antofagasta earthquake in northern Chile which occurred on 30th of July, 1995. It was a thrust-type event in the seismogenic zone between the subducting pacific Nazca plate and the overriding South American plate. In cooperation of the German Task Force for Earthquakes and the CINCA'95 project a network of up to 44 seismic stations was set up to record the aftershock sequence. The seaward extension of the network with 9 OBH stations increased significantly the precision of hypocenter determinations. They were distributed mainly on the fault plane itself around the city of Antofagasta and Mejillones Peninsula. The asperity structures were recognized here by the spatial variations of local seismological parameters; at first by the spatial distribution of the seismic b-value on the fault plane, derived from the magnitude-frequency relation of Gutenberg-Richter. The correlation of this b-value map with other parameters like the mainshock source time function, the gravity isostatic residual anomalies, the aftershock radiated seismic energy distribution and the vp/vs ratios from a local earthquake tomograhpy study revealed some ideas about the composition and asperity generating processes. The investigation of 295 aftershock focal mechanism solutions supported the resulting fault plane structure and proposed a 3D similar stress state in the area of the Antofagasta fault plane.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Universität Potsdam

Year

2005

Author dc:creator

• Sobiesiak, Monika

Contributors dc:contributor

• Zschau, Jochen

• Subduktionsbeben
• Nachbeben
• Bruchflaechenstruktur
• b-Wert Kartierung
• Herdmechanismen
• subduction earthquake
• aftershock sequence
• fault plane structure
• b-value map
• focal mechanisms

Repository record source_url

https://publishup.uni-potsdam.de/frontdoor/index/index/docId/218

OAI identifier oai:identifier

oai:kobv.de-opus4-uni-potsdam:218