High-resolution seismic reflection profiling of the Santa Monica Fault Zone, West Los Angeles, California
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Abstract
High-resolution seismic reflection data obtained across the Santa Monica fault in west Los Angeles reveal the near-surface geometry of this active, oblique-reverse-left-lateral fault. Although near-surface fault dips as great as 55° cannot be ruled out, we interpret the fault to dip northward at 30° to 35° in the upper few hundred meters, steepening to ≥65° at 1 to 2 km depth. A total of ∼180 m of near-field thrust separation (fault slip plus drag folding) has occurred on the fault since the development of a prominent erosional surface atop ∼1.2 Ma strata. In the upper 20 to 40 m strain is partitioned between the north-dipping main thrust strand and several closely spaced, near-vertical strike-slip faults observed in paleoseismologic trenches. The main thrust strand can be traced to within 20 m of the ground surface, suggesting that it breaks through to the surface in large earthquakes. Uplift of a ∼50,000-year-old alluvial fan surface indicates a short-term, dip-slip rate of ∼0.5 mm/yr, similar to the ∼0.6 mm/yr dip-slip rate derived from vertical separation of the oxygen isotope stage 5e marine terrace 3 km west of the study site. If the 0.6 mm/yr minimum, dip-slip-only rate characterizes the entire history of the fault, then the currently active strand of the Santa Monica fault probably began moving within the past ∼300,000 years.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | High-resolution seismic reflection profiling of the Santa Monica Fault Zone, West Los Angeles, California |
| Series title | Geophysical Research Letters |
| DOI | 10.1029/97GL01940 |
| Volume | 24 |
| Issue | 16 |
| Year Published | 1997 |
| Language | English |
| Publisher | American Geophysical Union |
| Description | 4 p. |
| First page | 2051 |
| Last page | 2054 |
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