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Shallow Structure and Geomorphology of the Hosgri Strike-Slip Previous HitFaultNext Hit, Offshore Central California

Johnson, Samuel Y.; Watt, Janet T.; and Hartwell, Stephen R.
[email protected]

We mapped a ~94-km-long portion of the right-lateral Hosgri Previous HitFaultNext Hit from Point Sal to Piedras Blancas in offshore central California using high-resolution seismic reflection profiles, marine magnetic data, and multibeam bathymetry. The database includes 121 seismic profiles across the Previous HitfaultNext Hit zone and is perhaps the most comprehensive reported survey of the shallow structure of an active strike-slip Previous HitfaultNext Hit. These data document the location, length, and near-surface continuity of multiple Previous HitfaultNext Hit strands, highlight Previous HitfaultNext Hit-zone heterogeneity, and demonstrate the importance of Previous HitfaultNext Hit trend, Previous HitfaultNext Hit bends, and Previous HitfaultNext Hit convergences in the development of shallow structure and tectonic geomorphology.

The Hosgri Previous HitFaultNext Hit is continuous through the study area passing through a broad arc in which Previous HitfaultNext Hit trend changes from ~ 338° to 328°. The southern ~40 km of the Previous HitfaultNext Hit zone in this area is more extensional, resulting in accommodation space that is filled by deltaic sediments of the Santa Maria River. The central ~24 km of the Previous HitfaultNext Hit zone is characterized by oblique convergence of the Hosgri Previous HitFaultNext Hit with the more northwest-trending Los Osos and Shoreline faults. Convergence between these faults has resulted in the formation of local restraining and releasing Previous HitfaultNext Hit bends, transpressive uplifts, and transtensional basins of varying size and morphology. We present a hypothesis that links development of a paired Previous HitfaultNext Hit bend to indenting of the Hosgri Previous HitFaultNext Hit by a strong crustal block translated to the northwest along the Shoreline Previous HitFaultNext Hit.

Two diverging Hosgri Previous HitFaultNext Hit strands bounding a central uplifted block characterize the northern ~30 km of the Hosgri Previous HitFaultNext Hit in this area. The eastern Hosgri strand passes through releasing and restraining bends; the releasing bend is the primary control on development of an elongate, asymmetric, "Lazy Z" sedimentary basin. The western strand of the Hosgri Previous HitFaultTop passes through a significant restraining bend and dies out northward where we propose that its slip transfers to active structures in the Piedras Blancas fold belt.


AAPG Search and Discovery Article #90162©2013 Pacific Section AAPG, SPE and SEPM Joint Technical Conference, Monterey, California, April 19-25, 2013