Title: An empirical study of the distribution of earthquakes with respect to rock type and depth

Abstract

Whether fault slip occurs seismically or aseismically depends on the frictional properties of the fault, which might be expected to depend on rock type and depth, as well as other factors. To view the effect of rock type and depth on the distribution of earthquakes, we compare geologic models of the San Francisco Bay and the Southern California regions to the distribution of seismicity. We normalize the number of earthquakes within each rock type and depth interval by the corresponding volume to determine the earthquake density. Earthquake density is confirmed primarily by depth, while whether the rock is sedimentary or basement has only a secondary, depth-dependent effect on the earthquake density. At very shallow depths, there is no difference in earthquake density between sedimentary and basement rocks. The earthquake density of basement rocks increases with depth more rapidly than that of sedimentary rocks to a similar but shallower maximum.

Authors:

Tal, Yuval ^[1]; Hager, Bradford H. ^[1]

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+ Show Author Affiliations

1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

Publication Date:

2015-08-26

Research Org.:

Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

Sponsoring Org.:

USDOE Office of Fossil Energy (FE)

OSTI Identifier:

1548282

Alternate Identifier(s):

OSTI ID: 1402359

Grant/Contract Number:  

FE0009738

Resource Type:

Accepted Manuscript

Journal Name:

Geophysical Research Letters

Additional Journal Information:

Journal Volume: 42; Journal Issue: 18; Journal ID: ISSN 0094-8276

Publisher:

American Geophysical Union

Country of Publication:

United States

Language:

English

Subject:

earthquake density; California seismicity; 3‐D geologic models; Gutenberg‐Richter