A Caltech Library Service

The 1994 Northridge Earthquake: 3-D crustal structure in the rupture zone and its relation to the aftershock locations and mechanisms

Zhao, Dapeng and Kanamori, Hiroo (1995) The 1994 Northridge Earthquake: 3-D crustal structure in the rupture zone and its relation to the aftershock locations and mechanisms. Geophysical Research Letters, 22 (7). pp. 763-766. ISSN 0094-8276. doi:10.1029/94GL03222.

PDF - Published Version
See Usage Policy.


Use this Persistent URL to link to this item:


A detailed 3-D P-wave velocity structure of the crust in the epicentral area of the 17 January, 1994 Northridge earthquake is determined by using 104,709 arrival times from 1673 Northridge aftershocks and 2948 other local earthquakes. A test performed using the data from the nearby portable stations suggests that the aftershock hypocenters relocated with the obtained 3-D model are accurate to about 2 km. We found that regions with high aftershock activity are generally associated with faster P-wave velocities. The velocity is high around the main south-dipping fault of the 1994 Northridge earthquake and the north-dipping fault of the 1971 San Fernando earthquake. A linear distribution of strike-slip aftershocks was found along a NE-SW boundary between high-velocity and low-velocity structures. To the west of this boundary a cluster of large shallow aftershocks with mixed mechanisms occurred in or near the border of a low-velocity area, while to the east aftershocks with thrust mechanisms occurred in a high-velocity area. These observations suggest that lateral variations of crustal properties are closely related to the fault segmentation in the Transverse Ranges. A better understanding of these features is important for long-term seismic hazard assessment in the Los Angeles area.

Item Type:Article
Related URLs:
URLURL TypeDescription
Kanamori, Hiroo0000-0001-8219-9428
Additional Information:Copyright 1995 by the American Geophysical Union. (Received September 19, 1994; accepted November 11, 1994.) Paper number 94GL03222. This work was funded by grants from the Southern California Earthquake Center (SCEC) and the National Science Foundation (EAR-9416120, EAR-8920136). We used the data prepared by the SCEC Data Center. H. M. Iyer, J. M. Lees and an anonymous referee critically read the manuscript and provided helpful comments. Contribution No. 5450, Division of Geological and Planetary Sciences, California Institute of Technology, and SCEC Publication No. 123.
Funding AgencyGrant Number
Southern California Earthquake Center (SCEC)UNSPECIFIED
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Caltech Division of Geological and Planetary Sciences5450
Southern California Earthquake Center (SCEC)123
Issue or Number:7
Record Number:CaltechAUTHORS:20141029-124953470
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:51009
Deposited By: George Porter
Deposited On:29 Oct 2014 20:21
Last Modified:10 Nov 2021 19:04

Repository Staff Only: item control page