Spatio‐temporal distribution of fault slip and high‐frequency radiation of the 2010 El Mayor‐Cucapah, Mexico earthquake

Abstract

Earthquake slip history and moment release are best resolved using long period seismic waves, but details in the rupture process, such as sharp changes in rupture velocity or direction, can be imaged more clearly using higher frequency waves. Here, we investigate the slip and the high‐frequency radiation histories of the 2010 El Mayor‐Cucapah, Baja California, Mexico earthquake (Mw 7.2). The slip distribution inferred from inversion of strong motion data between 0.02 and 0.25 Hz indicates northwest propagating rupture, followed by bilateral rupture for 40 s. The sources of high‐frequency radiation between 0.3 and 2 Hz inferred from back‐projection analysis using teleseismic data are adjacent to, but not within, the high‐slip patches from the finite slip model in time and space. This implies relatively smooth rupture during the times and regions of maximum moment release. As theoretical models have predicted, high‐frequency radiation seems mostly associated with changes in rupture velocity or slip magnitude. Strong high‐frequency radiation is also found where the rupture propagated to a branch fault 50‐km northwest of the hypocenter. Complementary constraints on both fault slip and high‐frequency radiation provide increased understanding of earthquake rupture mechanics and may help improve strong motion evaluation at high frequencies.