Tomographic P-wave velocity images of the Loma Prieta earthquake asperity

Journal Article · Wed Aug 01 00:00:00 EDT 1990 · Geophysical Research Letters (American Geophysical Union); (USA)

DOI:https://doi.org/10.1029/GL017i009p01433· OSTI ID:6400522

Lees, J M ^[1]

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1. Yale Univ., New Haven, CT (USA)

Tomographic inversion is applied to delay times from local earthquakes to image 3-D velocity variations surrounding the main rupture of the 1989 Loma Prieta earthquake. The 55{times}45 square km region is represented by blocks of 1 km per side laterally and by 8 layers of varying thickness to 18 km depth. High quality P-wave arrival times recorded on the USGS CALNET array from 549 crustal earthquakes with depths of 0 to 25 km were used as sources. Preliminary results note several velocity variations (5-12%) that correlate with specific characteristics of the 1989 rupture. These include prominent high-velocity anomalies near the mainshock hypocenter and prominent low-velocity anomalies where the dip of the San Andreas fault appears to change significantly. The termination of prominent low velocity features existing primarily in the hanging wall to depths of 7-9 km, correlates with the top of the rupture zone. High-velocity variations along the fault dominate where aftershock activity is high. The high velocity anomaly located at depth along the fault is interpreted as imaging the asperity on which the Loma Prieta earthquake occurred.

• OSTI ID: 6400522
• Journal Information: Geophysical Research Letters (American Geophysical Union); (USA), Vol. 17:9; ISSN 0094-8276
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CALIFORNIA
EARTHQUAKES
DATA ANALYSIS
AFTERSHOCKS
DEPTH
GEOLOGIC FAULTS
HYPOCENTERS
RUPTURES
SEISMIC ARRAYS
SEISMIC P WAVES
TIME DEPENDENCE
TOMOGRAPHY
US GS
VARIATIONS
WAVE PROPAGATION
DIAGNOSTIC TECHNIQUES
DIMENSIONS
FAILURES
FEDERAL REGION IX
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
MEASURING INSTRUMENTS
NATIONAL ORGANIZATIONS
NORTH AMERICA
SEISMIC EVENTS
SEISMIC WAVES
US DOI
US ORGANIZATIONS
USA
580000* - Geosciences