Prediction of maximum earthquake intensities for the San Francisco Bay region

Book · Wed Jan 01 00:00:00 EST 1975

OSTI ID:6756522

Borcherdt, R D; Gibbs, J F

The intensity data for the California earthquake of Apr 18, 1906, are strongly dependent on distance from the zone of surface faulting and the geological character of the ground. Considering only those sites (approximately one square city block in size) for which there is good evidence for the degree of ascribed intensity, the empirical relation derived between 1906 intensities and distance perpendicular to the fault for 917 sites underlain by rocks of the Franciscan formation is intensity = 2.69 - 1.90 log (distance) (km). For sites on other geologic units, intensity increments, derived with respect to this empirical relation, correlate strongly with the average horizontal spectral amplifications (AHSA) determined from 99 three-component recordings of ground motion generated by nuclear explosions in Nevada. The resulting empirical relation is intensity increment = 0.27 + 2.70 log (AHSA), and average intensity increments for the various geologic units are -0.29 for granite, 0.19 for Franciscan formation, 0.64 for the Great Valley sequence, 0.82 for Santa Clara formation, 1.34 for alluvium, and 2.43 for bay mud. The maximum intensity map predicted from these empirical relations delineates areas in the San Francisco Bay region of potentially high intensity from future earthquakes on either the San Andreas fault or the Hayward fault.

• OSTI ID: 6756522
• Resource Relation: Related Information: Open-File Report 75-180
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
EARTHQUAKE MAGNITUDE
FORECASTING
SAN FRANCISCO BAY
CALIFORNIA
EARTHQUAKES
EXPERIMENTAL DATA
GRAPHS
MAPS
RISK ASSESSMENT
DATA
INFORMATION
NORTH AMERICA
NUMERICAL DATA
PACIFIC OCEAN
SEAS
SEISMIC EVENTS
SURFACE WATERS
USA
WESTERN REGION
580201* - Geophysics- Seismology & Tectonics- (1980-1989)