There are two objectives to this project:

• Process data from the 33 Chi-chi aftershocks and other relevant crustal earthquakes in Taiwan.
• Compare Taiwan response spectral shapes as well as source (stress drop), path (Q(f)), and site (kappa) properties with those of tectonically active regions (e.g. California). The goal is to produce a processed data set consisting of time histories and response spectra for inclusion in the PEER strong motion database and to assess the appropriateness of including Taiwan crustal earthquakes with California data for regression analyses.

We will apply the same processing approach to these data as we used to process the Turkey and Chi-chi, Taiwan data previously for PEER. We will then parse the processed data into M, D (distance), and site category (e.g. rock, stiff soil, deep soft soil) bins and compare average horizontal component 5% damped response spectral shapes between Chi-chi main shock and aftershocks as well as with other Taiwan crustal earthquakes and with California data.

To estimate source, path, and site parameters, we will perform inversions using Fourier amplitude spectra on selected Taiwan earthquakes. The Chi-chi main shock and larger aftershocks as well as recorded Taiwan crustal earthquakes will be included. We would anticipate using at least twenty sites per earthquake and about twenty earthquakes. Emphasis will be placed on well-characterized sites through coordination with Professor Stokoe’s (2A02c) and Dr. Nigbor’s (2A02d) projects.

Project not yet started due to schedule demands of NGA Data Set project.

The strong-motion recordings from the M 7.6 Chi-chi Taiwan earthquake provide an important data set that could significantly impact our estimate of motions for future major earthquakes in California. Attenuation analysis in Project 1C01 shows that inclusion of Chi-Chi data would lead to a significant reduction (by 20% to 40%) of the median spectral value as well as a large increase of standard error (by 0.2 to 0.4 log unit). Before such changes are accepted for use in California, it is important to first answer the question of whether the Taiwan data can be used in California’s environment.

The objective of project 1E07 is to determine the levels of similarities of source, path, and site effects between the two regions of Taiwan and California. In this project, PI will conduct investigation of the source-path-site effects using data from shallow crustal earthquakes in Taiwan and compare his findings to those based on the California data alone. The Taiwan data used in this project should meet the same quality standard as the PEER strong motion database so these data could be incorporated into the PEER database at the end of the project. The data set should include recordings from the 33 Chi-chi aftershocks already processed in project 1E04 and other relevant strong-motion data from Taiwan. As a direct comparison of ground motion characteristics, PI will also compute statistical spectral shapes in several magnitude-distance bins and compare them to spectral shapes obtained from California data.

Processed Data for Taiwan earthquakes, assessment of similarity between Taiwan ground motions and those of California.