Temporal and spatial late Quaternary slip rate variability on the southern San Jacinto fault, California
Abstract
The history of the San Jacinto fault in accommodating Pacific-North America plate motion illustrates how deformation is partitioned in time and space across transform fault systems. We present new slip rate results from alluvial fans displaced by two parallel strands of the southern San Jacinto fault zone: the Clark and Coyote Creek faults. Alluvial fans were mapped in the field with 'B4' LiDAR imagery and dated using cosmogenic 10Be. We find that slip rates 1) varied synchronously by a factor of two over the past ~35 kyr and 2) change significantly along strike as slip is transferred southwestward from the Clark fault to the Coyote Creek fault. 35 ka to present average dextral slip rates for the Clark fault are 5.4 ± 2.2 mm/yr at the Rockhouse Canyon and 1.5 ± 0.4 mm/yr farther southeast, near the southern Santa Rosa Mountains. Over the same time period, the slip rate for the Coyote Creek fault is 2.9 ± 1.0 mm/yr. This yields a combined average slip-rate of 8.3 ± 2.2 mm/yr for the San Jacinto fault zone over the past ~35 kyr. Mid-Holocene to present rates are significantly faster along both fault strands. Displaced ~3-4 ka alluvial fans show that the Clark fault slips at a rate of 7.3 ± 1.8 mm/yr at Rockhouse Canyon and 3.9 ± 1.4 mm/yr at the southern Santa Rosa Mountians. Along the Coyote Creek fault the slip rate is 8.6 ± 2.9 mm/yr over the past ~3 ka. The combined Holocene rate of 15.9 ± 4.7 mm/yr is consistent with geodetic slip-rate estimates of 15 to 21 mm/yr for the San Jacinto fault zone. The apparently synchronous variation of slip-rate along both strands of the San Jacinto fault suggests that the rate of loading across the fault zone has varied significantly over the past ~35 kyr.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.T44B..08L
- Keywords:
-
- 8106 Continental margins: transform;
- 8107 Continental neotectonics (8002);
- 8111 Continental tectonics: strike-slip and transform