Characterization of Slip Behaviors Observed at the Bulnay Fault System in Mongolia

Abstract Large intraplate earthquakes faraway from plate boundaries are not well understood. In this study, we conduct a seismicity analysis of the earthquakes nearby one of the most active intraplate strike-slip fault in the world that is capable of producing magnitude-8 earthquakes. 72 seismic stations are deployed between 2012 and 2014 and record seismicity in Central Mongolia. We are able to identify two clusters of larger magnitude events locating near the end of the rupture zones from the 1905 earthquakes suggesting that they are the aftershocks from the 1905 earthquakes. We also identify a time period in November of 2012 with little to no seismic activity across the entire fault system. Other features such as mainshock-aftershock sequences, swarms, and repeating earthquakes are identified. Some of the repeating waveforms have significantly lower frequency that might be qualified as a low-frequency events (LFEs) or tremors. Further analysis using continuous wavelet transform to identify the dominant frequency is necessary to confirm whether these events are LFEs, tremors or regular earthquakes. A dense array of seismographs and GPS stations designed to look at the section of the Bulnay fault with relatively low seismity could help to justify whether creeps or slow-slip earthquakes exist in this area. Comparing the slip behaviors along the Bulnay fault system with other intraplate and interplate faults could elucidate the underlying mechanisms of the large intraplate earthquakes.