LATE QUATERNARY SLIP ON THE SANTA-CRUZ ISLAND FAULT, CALIFORNIA

Citation
N. Pinter et al., LATE QUATERNARY SLIP ON THE SANTA-CRUZ ISLAND FAULT, CALIFORNIA, Geological Society of America bulletin, 110(6), 1998, pp. 711-722
Citations number
58
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Geosciences, Interdisciplinary
ISSN journal
0016-7606
Volume
110
Issue
6
Year of publication
1998
Pages
711 - 722
Database
ISI
SICI code
0016-7606(1998)110:6<711:LQSOTS>2.0.ZU;2-5
Abstract
The style, timing, and pattern of slip on the Santa Cruz Island fault were investigated by trenching the fault and by analysis of offset lat e Quaternary landforms. A trench excavated across the fault at Christi Beach, on the western coast of the island, exposed deformation of lat est Pleistocene to Holocene sediments and pre-Quaternary rocks, record ing repeated large-magnitude rupture events. The most recent earthquak e at this site occurred ca. 5 ka. Coastal terraces preserved on wester n Santa Cruz Island have been dated using the uranium-series technique and by extrapolation using terrace elevations and the eustatic record . Offset of terraces and other landforms indicates that the Santa Cruz Island fault is predominantly left lateral, having a horizontal slip rate of not more than 1.1 mm/yr and probably about 0.8 mm/yr. The faul t also has a smaller reverse component, slipping at a rate of between 0.1 and 0.2 mm/yr. Combined with measure ments of slip per event, this information suggests a long-term average recurrence interval of at le ast 2.7 k.y. and probably 4-5 k.y., and average earthquake magnitudes of Mw 7.2-7.5. Sense of slip, recurrence interval, and earthquake magn itudes calculated here for the Santa Cruz Island fault are very simila r to recent results for other faults along the southern margin of the western Transverse Range, including the Malibu Coast fault, the Santa Monica fault, the Hollywood fault, and the Raymond fault, supporting t he contention that these faults constitute a continuous and linked fau lt system, which is characterized by large but relatively infrequent e arthquakes.