HR: 17:00h
AN: S24A-05    [Abstracts]
TI: Modeling Site Response with Considering Nonlinearity and Characteristics of Spatial Variation
AU: * Tsuda, K
EM: kenichi@crustal.ucsb.edu
AF: Institute for Crustal Studies, University of California Santa Barbara, Institute for Crustal Studies, University of California Santa Barbara, Santa Barbara, ca 93106 United States
AU: Archuleta, R
EM: ralph@crustal.ucsb.edu
AF: Institute for Crustal Studies, University of California Santa Barbara, Institute for Crustal Studies, University of California Santa Barbara, Santa Barbara, ca 93106 United States
AB: Accounting for site response is essential for realistic predictions of ground motion prediction from future earthquakes. Many observations from recent large earthquakes indicate that using only linear theory to model site response is not enough i.e., considering nonlinearity of site response is necessary. Since the coherency, usually used to consider the spatial variation of ground motion, is only dependent on the phase information, i.e., no amplitude information is included, it is impossible to estimate spatial variation of (amplitude) site response based on observed records of ground motion. In order to model site response with consideration of these two factors, we have analyzed data from a relatively dense seismic array located near the city of Sendai, Japan. This array constitutes of 29 stations: 20 managed by Tohoku Institute of Technology, 6 by Building Research Institute, and 3 by NIED within an area of 20 x 30 kmę. This array is located close to one of the most active subduction zones in Japan. Consequently, this Sendai array has numerous weak motion records from moderate-sized earthquakes well as strong motion records from two large earthquakes, 2003 (Mw 7.0) and 2005 (Mw 7.1) Miyagi-oki earthquakes. We first estimate the surface site response for all 29 stations by using the method developed by Tsuda et al. (2005); this method does not depend on a reference site. After deriving a site response at each station, we compute a "Site Correlation Coefficient (SCC)", which is based on the known site responses for all pairs of stations within the array. Using the results of SCC, we can predict the site response for other locations within the array where we do not have recordings. To examine nonlinearity, we compared the site response based on weak motion data with site response based on strong motion data from two large earthquakes. There is significant nonlinearity at many sediment stations. Because different stations have different levels of strong shaking, we analyze soil nonlinearity and its dependence on the level of the input motion.
DE: 7200 SEISMOLOGY
DE: 7203 Body waves
DE: 7212 Earthquake ground motions and engineering seismology
SC: Seismology [S]
MN: Fall Meeting 2005