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ETAS: Estimated aftershock Seismicity (Research Product) Created by: JPL E-DECIDER, UC Davis Point(s) of Contact: Margaret T. Glascoe (JPL), Mark R. Yoder (UC Davis) Region: Impacted area: Nepal and border regions of neighboring countries Date: 2015-05-01 Generated: 2015-05-12 |
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Description: In the weeks, months, and even years following a large mainshock, aftershocks can pose significant, persistent seismic hazard. This map uses a variant of ETAS, an algorithm based on known, well understood properties of earthquakes and aftershock behaviors, to estimate the rates and spatial distributions of aftershock seismicity following a mainshock. In this implementation, the aftershock productivity for all earthquakes within the past 5 years is calculated and aggregated for each point on a 0.1° x 0.1° lattice covering the study area. The seismicity contribution diminishes with increasing time and distance between each location-earthquake pair, so the entire catalog can be used objectively, and the process can be operated in an automated fashion. Intuitively, this method renders a quantitative, graphical representation of recent, large earthquakes -- and of course their subsequent aftershock seismicity. "Warm" colors (red, orange) indicate high rates; "cool colors" indicate lower seismicity. Generally, we expect aftershock hazard to cluster around the epicenters of the larger earthquake epicenters. Large aftershocks, however, often occur farther away - more or less near the boundary of the mainshock rupture, so it is not unusual to observe concentrations of aftershock hazard significantly separated from the immediate mainshock region, particularly for large earthquakes. The ETAS product should be used as a concise representation of recent seismicity, in general, and to estimate the relative local intensity of aftershocks and other types of triggered seismicity within the vicinity of a recent, large earthquake. Typically, this implies earthquakes with magnitude lower than the mainshock, but foreshock scenarios (in which an aftershock has greater magnitude than its parent event) are also possible. Data Source(s): ETAS model: Yoder et al. 2014, earthquake catalog from ANSS query. Graphics: Earthquakes KML courtesy of USGS, image rendered using Google Earth. Link: KML More Information: Hyperlink above points to the most recent KML. Additional products, including images and previous forecasts) can be found at: http://e-decider.org/content/nepal-earthquake-april-2015. |
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