Spatial and Temporal Variation of LURR and its Implication for the Tendency of Earthquake Occurrence in Southern California

— Based on the theory of LURR and its recent development, spatial and temporal variation of Y/Y _c (value of LURR/critical value of LURR) in the Southern California region during the period from 1980 through March, 2001 was studied. According to the previous study on the fault system and stress field in Southern California, we zoned the Southern California region into 11 parts in each of which the stress field is almost uniform. With the time window of one year, time moving step of three months, space window of a circle region with a radius of 100 km and space moving step of 0.25 degree in latitude and longitude direction, the evolution of Y/Y _c were snapshot. The scanning results show that obvious Y/Y _c anomalies occurred before 5/6 of strong earthquakes considered with a magnitude of 6.5 or greater. The critical regions of Y/Y _c are near the epicenters of the strong earthquakes and the Y/Y _c anomalies occur months to years prior to the earthquakes. The tendency of earthquake occurrence in the California region is briefly discussed on the basis of the examination of Y/Y _c .