Journal
GEOPHYSICAL RESEARCH LETTERS
Volume 40, Issue 23, Pages 6064-6068Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1002/2013GL058109
Keywords
earthquake; intermediate depth; fracture energy; efficiency; source scaling; thermal runaway
Categories
Funding
- NSF [EAR-1045684]
- Division Of Earth Sciences
- Directorate For Geosciences [1045684] Funding Source: National Science Foundation
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Intermediate-depth earthquakes occur at depths where temperatures and pressures exceed those at which brittle failure is expected. There are two leading candidates for the physical mechanism behind these earthquakes: dehydration embrittlement and self-localizing thermal shear runaway. A complete energy budget for a range of earthquake sizes can help constrain whether either of these mechanisms might play a role in intermediate-depth earthquake rupture. The combination of high stress drop and low radiation efficiency that we observe for M-w 4-5 earthquakes in the Bucaramanga Nest implies a temperature increase of 600-1000 degrees C for a centimeter-scale layer during earthquake failure. This suggests that substantial shear heating, and possibly partial melting, occurs during intermediate-depth earthquake failure. Our observations support thermal shear runaway as the mechanism for intermediate-depth earthquakes, which would help explain differences in their behavior compared to shallow earthquakes.
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