Annually, the Seismological Society of America (SSA) recognizes excellence in student research with its Student Presentation Award. This year's list of eight recipients includes IRIS Internship alumni Justin Brown (Class of 2004). Justin was recognized for his continued efforts to better understand factors that influence Tremor (abstract below). Congratulations Justin! Justin was also recognized by the SSA community with a previous Student Presentation Award in 2008.
Be sure to browse the lists of past recipients when visiting the SSA website as other program alumni have also won this award.
Tectonic tremor from multiple circum-Pacific subduction zones has been shown to consist of repeating low frequency earthquakes on the plate interface. Tremor/LFE occurrence in some areas exhibits episodic behavior down-dip of previous great mega-thrust earthquakes suggesting that the tremor may delimit the lower edges of large earthquake rupture. We investigate where and why tremor does (and does not) occur. We compare observations of LFE locations in five subduction zones: southwest Japan, Cascadia, Alaska-Aleutian Arc, Costa Rica and Mexico. We compare the LFE location patterns among the five areas with subduction parameters such as incoming sediment thickness, plate age, convergence rate and temperature. A preliminary conclusion is that temperature exerts a strong influence on LFE depth; warmer subduction zones (e.g. southwest Japan, Cascadia) experience tremor activity around 30-40 km depth, whereas cooler subduction zones (e.g. the Alaska-Aleutian Arc) experience tremor between 45-55 km depth. In addition, sediment thickness seems to play little to no role in tremor/LFE depths. This may be attributable to the amount of shear and chemical alterations that occur in the primary seismogenic zone up-dip from the tremor zone.