Intraplate Induced Earthquakes: Investigating Two Potential Events

In this project we investigate the characteristics of two recent intraplate seismic events to better understand earthquake swarms and induced seismicity. These events include a M = 5.3 earthquake potentially induced by mining activities in Duncan, Arizona, and a swarm of earthquakes in Northeastern state of Nuevo Leon, Mexico potentially induced by fluid injection. For each region, we investigate characteristics including b-values, stress drop, events distribution pattern and seismic waves properties. For the case in Arizona, we investigate a potential case of earthquakes induced by mining activities. We examined 594 seismic events that occurred in an area encompassing the Morenci mine and the epicentral location of a M 5.3 earthquake in southeastern Arizona to determine whether mining activity contributed to the M 5.3 earthquake. Based on our observations, we suggest that most of the events, smaller than the M 5.3, correspond to blasting at the mine or were directly induced by nearby mine blasts. We performed a FEM numerical model that suggests the stress change caused by the removal of material from the mine was not large enough to trigger the M 5.3 earthquake. However, the numerical model does indicate the stress change was large enough to potentially overstress nearby faults which is supported by the temporal and spatial distribution of smaller earthquakes in this region. For case in Nuevo Leon, we investigate a potential case of earthquakes induced by fluid injection. We examined 281 earthquakes in Nuevo Leon to determine whether these earthquakes correlate to fluid injection by shale gas wells. Based on our observations, we suggest that earthquakes that surround to shale gas wells Tangram-1, Nerita-1, Batial-1 and Kerner-1 are induced by their fluid injection. Earthquakes that are in the mountain or close to mountain front are tectonic earthquakes. We performed b-value analysis that suggest earthquakes that surround to shale gas wells are induced earthquakes, and earthquakes that close to Mojave-Sonora megashear are tectonic earthquakes. We further performed temporal and spatial analysis for the distribution of all earthquakes which support the suggestion of b-value analysis.