Reassessment of the 1892 Laguna Salada earthquake - fault kinematics and rupture patterns

Thomas K. Rockwell, John M. Fletcher, Orlando J. Teran, Karl J. Mueller, James B. Salisbury, Sinan O. Akciz, Petra Stepancikova, & Susan E. Hough

Submitted 2014, SCEC Contribution #1961

We present results of intensive field investigations of the scarp associated with the 23 February 1892 earthquake in northern Baja California. Newly recognized additional displacement suggests it accommodated a rupture about 58 km in length, twice as long as previous estimates. Slip produced in the 1892 event varied from purely dextral slip near the international border to roughly 1:1 oblique-normal slip farther south along the 2-4 km deep portion of the Laguna Salada Basin. The length of the 1892 rupture with oblique-normal slip comprises a number of short, poorly organized and discontinuous fault scarps whose heights vary in concert with their strike. Slip was linked farther south to a short, purely normal fault that forms a large releasing bend at the southern termination of the fault zone. Given the distribution of slip along the earthquake and a likely range of locking depths, we conclude the 1892 earthquake was between Mw 7.1-7.3 in magnitude, consistent with previous estimates from macroseismic observations. The length of the Laguna Salada fault that ruptured in 1892 also accommodated minor normal sense displacement along much of its length in the recent 2010 Mw 7.2 El Mayor-Cucapah earthquake, which guided the re-mapping effort.

Rockwell, T. K., Fletcher, J. M., Teran, O. J., Mueller, K. J., Salisbury, J. B., Akciz, S. O., Stepancikova, P., & Hough, S. E. (2014). Reassessment of the 1892 Laguna Salada earthquake - fault kinematics and rupture patterns. Bulletin of the Seismological Society of America, (submitted).