- © 2014 by the Seismological Society of America
A local magnitude (ML) 4.4 earthquake occurred near the town of Paradox, in western Colorado, on 24 January 2013, at 4:46:39 UTC time (23 January 2013, at 9:46:39 p.m. local time) and was strongly felt in nearby communities. Earthquakes this large are infrequent in the region. A search of regional earthquake databases yields just nine previous earthquakes of magnitude 3.5 or larger recorded since 1985, and occurring within 200 km of the January 2013 earthquake epicenter (Fig. 1). Of these nine earthquakes, the epicenters of four are within several kilometers of an active brine deep injection well, and, based on their timing and location, we interpret them to be induced by injection operations.
The 24 January 2013 earthquake was recorded by the Paradox Valley Seismic Network (PVSN), a local 20‐station surface array of broadband three‐component seismometers installed to monitor earthquakes induced by fluid injection at the Paradox Valley Unit (PVU) deep brine disposal well. PVSN has been continuously operated in various configurations since 1985, including a six‐year pre‐injection baseline period. Ground motions from the January 2013 earthquake were also recorded by strong‐motion instruments at three free‐field sites located between 5 and 12 km from the epicenter. In this article, we provide analyses of the January 2013 event based on data from the local seismic network and strong‐motion instruments. We compare the …