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The Emerson Lake Body: A link between the Landers and Hector Mine earthquakes, southern California, as inferred from gravity and magnetic anomalies

Bulletin of the Seismological Society of America

By:
and
DOI: 10.1785/0120000906

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Abstract

Gravity and magnetic data indicate a mafic crustal heterogeneity that lies between the Hector Mine 16 October 1999 (Mw 7.1) and Landers 28 June 1992 (Mw 7.3) epicenters. The aftershocks and ruptures of these two events avoided the interior of the body. Two- and three-dimensional modeling of the potential-field anomalies shows that the source, here named the Emerson Lake body (ELB), extends to a depth of approximately 15 km. The source of the gravity and magnetic anomaly is most likely Jurassic diorite because exposures of these rocks coincide with both gravity and magnetic highs west of Emerson Lake. Seismic tomography also shows higher velocities within the region of the ELB. We propose that the ELB was an important influence on the rupture geometry of the Landers and Hector Mine ruptures and that the ELB may have played a role in transferring of stress from the Landers earthquake to the Hector Mine hypocenter. Seismicity before the Landers earthquake also tended to avoid the ELB, suggesting that the ELB affects how strain is distributed in this part of the Mojave Desert. Thus, faults within the body should have limited rupture sizes and lower seismic hazard than faults bounding or outside this mafic crustal heterogeneity.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
The Emerson Lake Body: A link between the Landers and Hector Mine earthquakes, southern California, as inferred from gravity and magnetic anomalies
Series title:
Bulletin of the Seismological Society of America
DOI:
10.1785/0120000906
Volume
92
Issue:
4
Year Published:
2002
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Bulletin of the Seismological Society of America
First page:
1606
Last page:
1620
Number of Pages:
15