Seismicity and Faulting in the Southern gulf of California

Seismicity and Faulting in the Southern gulf of California Figure 1.
<p> Location of the SCOOBA OBS stations (triangles), as well as complementary on-shore broad- band NARS-Baja stations (blue squares). Also shown are Global CMT mechanisms for seven large events recorded by the array, our modeled mechanism for the 27 November 2005 event, and the locations for ~300 of our best-located events (black circles).
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The Sea of Cortez Ocean-Bottom Array (SCOOBA) seismic experiment consists of a 4-component broadband ocean-bot- tom seismic (OBS) array that recorded earthquakes and other natural seismic signals for nearly 12 months between October 2005 and October 2006. The 14-station array was designed to complement the onshore NARS-Baja experiment run by Utrecht University, Cal Tech, and CICESE. Two subarrays were centered within the Alarcon and Guaymas basins, coinciding with previous refraction and MCS lines [Lizarralde et al., 2007], with ~20 km spacing. Four additional instruments were deployed at ~100 km spacing. Over 650 earthquakes (depths < 35 km) were recorded by the array, with ~320 M>3.5 earthquakes and seven M>5 strike-slip events within the southern gulf that are accompanied by several foreshocks and aftershocks. Most of these events are located on the major NW-SE strike slip faults that delineate the plate boundary, but a few appear to be located on faults well away from the nominal plate boundary. For sufficiently well-recorded and paired events, we are in the process of applying the hypoDD double-difference algorithm to obtain high-precision relative relocations. Additionally, we are working towards modeling the Rayleigh waves of ~30 events to determine the mechanisms of on- and off-axis activity. These locations and mechanisms of earthquake activity will improve our understanding of the distribution of seismic deformation within the greater extensional zone in the southern GoC. These data have been archived at the IRIS DMC, and are openly available to the community.
</p><p>References
</p><p>Lizarralde, D., G. J. Axen, H. E. Brown, J. M. Fletcher, A. Gonzalez-Fernandez, A. J. Harding, W. S. Holbrook, G. M. Kent, P. Paramo, F. Sutherland and P. J. Umhoefe, Variation in the styles of rifting in the Gulf of California, Nature, 448, 466-469, 2007.
</p><p>Acknowledgements: Funding is from the NSF MARGINS program, award number OCE 0436411 for James Gaherty at LDEO, and OCE 0305140 for John Collins at WHOI.</p>

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