Introduction

The Northern California Seismicity Project (NCSP) is a counterpart to the San Francisco Bay Region (SFBR) - Historical Earthquake Re-analysis Project (HERP) which has been reported upon in previous annual reports. The initial objective of this project which commenced in August, 2000, is to transcribe the pre-1984 data for M$_{L} \geq$ 2.8 earthquakes which have occurred in Northern and Central California (NCC) (outside of the SFBR covered by HERP), from the original reading/analysis sheets, kept on store in the Berkeley Seismological Archives, to a computer readable format.

Characterization of the spatial and temporal evolution of NCSP seismicity during the initial part of the earthquake cycle as the region emerges from the stress shadow of the great 1906 San Francisco earthquake is the long term goal. The problem is that the existing BSL seismicity catalog for the SFBR, which spans most of the past century (1910-present), is inherently inhomogeneous because the location and magnitude determination methodologies have changed, as seismic instrumentation and computational capabilities have improved over time. As a result, NCC seismicity since 1906 is poorly understood.

Creation of a NCC seismicity catalog that is homogeneous, that spans as many years as possible, and that includes formal estimates of the parameters and their uncertainty is a fundamental prerequisite for probabilistic studies of the NCC seismicity. The existence of the invaluable BSL seismological archive, containing the original seismograms as well as the original reading/analysis sheets, coupled with the recently acquired BSL capability to scan and digitize historical seismograms at high resolution allows the application of modern analytical algorithms towards the problem of determining the source parameters of the historical SFBR earthquakes.

Berkeley Seismological Laboratory
215 McCone Hall, UC Berkeley, Berkeley, CA 94720-4760
Questions or comments? Send e-mail: www@seismo.berkeley.edu
© 2005, The Regents of the University of California