THE IRIS RESPONSE TO THE VIRGINIA EARTHQUAKE AND OPPORTUNITIES AS THE USARRAY ENTERS EASTERN NORTH AMERICA

Within five days of the August 23, 2011 Mineral, Virginia earthquake, the IRIS Rapid Array Mobilization Program (RAMP) had deployed a temporary array of seven broadband seismometers across the epicenter region. Investigators at Lehigh University subsequently took over the operation of these temporary stations. The NSF-funded EarthScope USArray program also provided portable, short-period seismometers for dense deployments led by investigators at Cornell and Virginia Tech to conduct a high-resolution aftershock survey and produce structural images of the epicenter region using the aftershocks as sources. These RAMP datasets provided an unprecedented level of detail for studying a moderate magnitude intraplate earthquake.

In the coming months, EarthScope is poised to address the continued questions and concerns about seismicity in eastern North America. IRIS operates EarthScope’s USArray, which deploys seismic instruments to provide detailed observation of geologic targets across North America. The seismic USArray consists of a Transportable Array (TA), Flexible Array (FA), and Reference Network. The TA stations are three-component broadband seismometers that are deployed for about two years, arranged in a grid with ~70 km separation between stations. The FA maintains a pool of instruments, ranging from high-frequency geophones to three-component broadband sensors, which are often deployed in arrays for days to years to investigate local or regional features. Deployment of TA stations is approaching the foothills of the Appalachian Mountains and there are already several PI-driven FA experiments along or east of the Mississippi River.

Besides the Virginia earthquake, the eastward migrating TA has captured prominent recent intraplate seismicity in Arkansas and Oklahoma with high resolution. We will present the current status of USArray activities and sample key observations related to these recent earthquakes. We will also provide an overview of USArray deployment plans as a means to facilitate and encourage collaborative investigations and discuss opportunities for the earth science community to leverage the FA and TA to better understand the seismicity and tectonics of eastern North America.