Delayed Dynamic Triggered Seismicity in Northern Baja California, México Caused by Large and Remote Earthquakes

Abstract

We analyze the seismicity in northern Baja California, Mexico, that occurred one month before and one month after the 11 March 2011 ( M w 9.1) Tohoku‐Oki, Japan, earthquake and for two other large and remote earthquakes, the 27 February 2010 central Chile ( M w 8.8) earthquake and the 11 April 2012 northern Sumatra earthquake ( M w 8.6). The northern region of Baja California exhibits high microseismic activity and moderate‐size earthquakes. The seismicity in this region is monitored by the seismic network Red Sismica del Noroeste de Mexico (RESNOM) operated by the Centro de Investigacion Cientifica y de Educacion Superior de Ensenada (CICESE). We use the RESNOM seismic catalog to search for changes in local seismic rates that occurred after the passing of surface waves generated by the three large earthquakes studied. When we compare one month of seismicity before and after the M w 9.1 Japan earthquake, in the biggest of the three events analyzed, we observe the absence of triggered seismicity in the northern Peninsular Ranges and an increase of seismicity south of the Mexicali Valley, where the Imperial fault jumps southwest and the Cerro Prieto fault continues south. We also observe an increase of seismicity rate in the Cucapah fault and in the San Pedro Martir fault regions. The Cucapah fault region, the most active of the three regions during the studied period, shows an increase of seismicity several days after the 2010 Chile ( M w 8.8) and the 2011 Japan ( M w 9.1) earthquakes. This observation can be interpreted as evidence of delayed seismicity and confirms the observation of Rubinstein et al. (2009) that earthquakes tend to be triggered in regions with high ambient seismicity rates. We observed delayed triggering of earthquakes generated by two of the three remote earthquakes analyzed. These observations can be explained by dynamic triggering of prolonged fault creep as proposed by Shelly et al. (2011). Online Material: Maps of seismicity and M c.