Triggered reverse fault and earthquake due to crustal unloading, northwest Transverse Ranges, California
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Abstract
A reverse-right-oblique surface rupture, associated with a ML 2.5 earthquake, formed in a diatomite quarry near Lompoc, California, in the northwesternmost Transverse Ranges on April 7, 1981. The 575-m-long narrow zone of ruptures formed in clay interbeds in diatomite and diatomaceous shale of the Neogene Monterey Formation. The ruptures parallel bedding, dip 39°–59°S, and trend about N84°E on the north limb of an open symmetrical syncline. Maximum net slip was 25 cm; maximum reverse dip slip was 23 cm, maximum right-lateral strike slip was about 9 cm, and average net slip was about 12 cm. The seismic moment of the earthquake is estimated at 1 to 2 × 1018 dyne/cm and the static stress drop at about 3 bar. The removal of an average of about 44 m of diatomite resulted in an average load reduction of about 5 bar, which decreased the normal stress by about 3.5 bar and increased the shear stress on the tilted bedding plane by about 2 bar. The April 7,1981, event was a very shallow bedding-plane rupture, apparently triggered by crustal unloading.
Suggested Citation
Yerkes, R.F., Ellsworth, W., and Tinsley, J.C., 1983, Triggered reverse fault and earthquake due to crustal unloading, northwest Transverse Ranges, California: Geology, v. 11, no. 5, p. 287-291, https://doi.org/10.1130/0091-7613(1983)11<287:TRFAED>2.0.CO;2.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Triggered reverse fault and earthquake due to crustal unloading, northwest Transverse Ranges, California |
| Series title | Geology |
| DOI | 10.1130/0091-7613(1983)11<287:TRFAED>2.0.CO;2 |
| Volume | 11 |
| Issue | 5 |
| Year Published | 1983 |
| Language | English |
| Publisher | Geological Society of America |
| Description | 5 p. |
| First page | 287 |
| Last page | 291 |