Earthquake motion simulation and reliability implications

Seismic forces have been a most important consideration in design of structures in California. Although Mid-America is a region of low to moderate seismicity, infrequent moderate to large events have occurred in the past and can occur again and cause large losses. The performance of the building stock and other structures under future earthquakes is therefore a serious concern in California as well as in Mid-America.; For purpose of performance evaluation, a phenomenological model is developed for generation of earthquake motions in Mid-America and California. The simulation procedure is based on the latest information of seismicity, the most recent ground motion models and simulation methods appropriate for engineering applications in the corresponding regions. In view of the difference in earthquake records and seismotectonic data available, the simulation method for California is based more on data and that for Mid-America more on theories and models due to lack of strong motion records. A strong emphasis is placed on uncertainty modeling and efficiency in application to performance evaluation and reliability analysis. The procedure may be improved as more knowledge on earthquakes in the corresponding regions and more accurate and efficient methods of ground motion modeling become available.; Site locations of special interest are Santa Barbara CA, Memphis TN, Carbondale IL, and St. Louis MO. Since ground motions are strongly dependent on local soil condition and yet the soil profile variation within a city has not been mapped in detail, the soil condition of a city is assumed to have small variation and can be approximately modeled by a generic profile. Ground motions at bedrock, however, are also generated for the Mid-America cities such that if detailed information of local soil variation is available, one can use appropriate soil amplification computer software to obtain the surface ground motions. Suites of uniform hazard ground motions are selected from a large pool of simulated earthquakes to represent the seismic hazard from the causative faults surrounding a given site location. These ground motion suites allow an accurate and efficient evaluation of structural performance and reliability and are available on the web at http://mae.ce.uiuc.edu/Research/RR-1/GMotions/Index.html.