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ML 3.8 Devore Earthquake - 4/28/12
The 30th of April, 2012
(Anthony Guarino, Egill Hauksson, Lucy Jones, Kate Hutton) Version 1.0
A M3.8 earthquake occurred 3km WNW of Devore, CA at 8:07 AM on Saturday, April 28th, 2012. Although close in proximity to the San Andreas fault, this event generated a Moment Tensor and Focal Mechanism consistent with thrust faulting. A San Andreas event would be more consistent with strike-slip motion (lateral). Due to the complex geology of the area, located near where the San Bernardino and San Gabriel mountains meet, a causative fault is more difficult to identify with certainty.
Earthquakes of this magnitude rarely, if ever, create surface rupture. Mapping a surface rupture for an event helps identify which fault(s) rupture. Since not all earthquakes produce surface rupture, aftershock sequences may be mapped to identify the trend of the rupture for larger events (such as the 1994 M6.7 Northridge earthquake, which occurred on a blind thrust fault that did not rupture the surface of the earth). Smaller earthquakes produce few, if any, aftershocks, so this method of identifying the fault is not applicable in this case, as there are only a few aftershocks for this event. Link to summary of the 1994 Northridge Earthquake
This earthquake produced four aftershocks, ranging in magnitude from 1.4-2.0. They were all located within on km of the mainshock. Aftershocks may continue with this sequence, but it would not be surprising if no more aftershocks occurred, as the frequency of aftershocks decays with time. There were no foreshocks in the immediate area (within 1km), and although earthquakes in Southern California have about a 5% probability of being a foreshock to a larger event, this probability decays rapidly with time as well. Since so much time has passed since the mainshock, it is less and less likely that a larger event would occur.
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