Seminar on Strong Motion Seismology

Date: 27 November, 2006 (Mon.) 1000-1200
Place: Room #570, 5th floor of DPRI main building
Speaker: Dr. Luis Angel Dalguer (Department of Geological Science, San Diego State University, USA)
Title: Accuracy of Dynamic Rupture Models and their Potential Application to Study Different Aspects of Earthquakes Phenomena
Abstract: Contrary to kinematic models, dynamic rupture models investigate the physical processes involved in the fault rupture, incorporating conservation laws of continuum mechanics, constitutive behavior of rocks under interface sliding, and state of stress in the crust. These earthquake physic models have the potential to contribute to our understanding of the physical causes of the rupture process, and therefore to improve our capability for predicting source-dominated ground motion phenomena. But appropriate numerical model is important to avoid misleading conclusions, due to numerical bias, that may have significant implications when evaluating earthquake problems. Here we assess the accuracy of different fault representation methods and demonstrate that appropriate fault representation in a numerical scheme is crucial to reduce uncertainties in numerical simulations of earthquake source dynamics and ground motion, and therefore important to improving our understanding of earthquake physics in general. In addition to other potential applications of dynamic models, here we discuss the importance of high resolution models of large scale earthquake to study two open subjects of ongoing debate: (1) rupture at bimaterial interface in 3D and the mechanism for exciting the prefered-direction unilateral rupture, and (2) the difference of faulting and near source ground motion of surface and buried earthquakes.
Speaker: Dr. Rafael Benites (Institute of Geological and Nuclear Sciences, New Zealand)
Title: A ground motion transfer function matrix for two nearby rock and soil sites
Abstract: I attempt to compute local site effects based on a matrix transfer function that incorporates the coupling among the three components of motion of a soil and a rock (reference) sites. The matrix is obtained from a generalized inverse formulation, considering the records of many earthquakes incident from a wide range of azimuths and depths, at both sites. The formulation also incorporates the covariance among the three components for all the earthquakes. The method is applied to calculate the amplification factors of the strong ground motion network sites in the Wellington Region, New Zealand, showing the main features produced by the standard spectral ratios, the cross coupling effects, and the directions of maximum amplitude.