This is her abstract for the Dec AGU meeting in San Fran

S31G-07
Remotely Triggered Earthquakes in Intraplate Regions: Distributed Hazard, Dependent Events

Hough, S E, Mueller, K, Bilham, R , Ambraseys, N, Martin, S

The central and eastern United States has experienced only 5 historic earthquakes with Mw above 7.0, the 1886 Charleston earthquake and four during the New Madrid sequence of 1811-1812 (three principal mainshocks and the so-called ``dawn aftershock'' following the first mainshock.) Careful consideration of historic accounts yields compelling evidence for a number of remotely triggered earthquakes in both 1812 and 1886, including several events large enough to be potentially damaging. We propose that one of the (alleged) New Madrid mainshocks, on 23 January 1812, may itself be a remotely triggered earthquake, with a location some 200 km north of the New Madrid Seismic Zone. Our proposed source location is near the location of the 1968 southern Illinois earthquake, which occurred on a blind thrust fault at 20-25 km depth. Intensity data for the 1812 event are consistent with expectations for a similarly deep event.

Such triggered events presumably do not represent a wholly new source of hazard but rather a potential source of dependent hazard. That is, the common assumption is that the triggering will cause only a ``clock advance,'' rather than causing earthquakes that would not have otherwise occurred. However, in a low strain-rate region, a given dynamic stress change can potentially represent a much larger clock advance than the same change would cause in a high strain-rate region.

Moreover, in regions with low seismicity and a short historic record, overlooked remotely triggered historic earthquakes may be important events. It is thus possible that significant events are currently missing from the historic catalogs. Such events--even if large--can be difficult to identify without instrumental data. The (interplate) 1905 Kangra, India earthquake, further illustrates this point. In this case, early seismic records provide corroboration of an early triggered event whose existence is suggested--but difficult to prove--based on detailed macroseismic data.

In the central United States, where even moderate earthquakes are uncommon, our results suggest that the largest known historic earthquakes in three states (Kentucky, Illinois, and Mississippi) may have been remotely triggered earthquakes.

http://pasadena.wr.usgs.gov/office/hough
2003 Fall Meeting