TY - JOUR
T1 - Thermal-petrological controls on the location of earthquakes within subducting plates
AU - Abers, Geoffrey A.
AU - Nakajima, Junichi
AU - van Keken, Peter E.
AU - Kita, Saeko
AU - Hacker, Bradley R.
N1 - Funding Information:
The ideas presented in this paper nucleated at a Sendai G-COE Symposium (2010) and we thank the conference sponsors. Data in the U.S. were all collected on a variety of projects sponsored by the National Science Foundation (NSF EAR-0545441 ). Thermal modeling was supported by NSF 0646757 and 084048 . This work was supported in part by the Ministry of Education, Culture, Sports, Science and Technology of Japan , under its Observation and Research Program for Prediction of Earthquakes and Volcanic Eruptions, and by the Global COE Program, Global Education and Research Center for Earth and Planetary Dynamics, Tohoku University. LDEO Contribution number 7679.
PY - 2013/5
Y1 - 2013/5
N2 - We find that in young and warm subducting plates, earthquakes occur just below the Moho. In older plates, earthquakes occur throughout the subducting oceanic crust, as well as the subducting mantle. We document this behavior in several subduction zones where there are independent constraints on earthquake locations and slab structure, specifically for northern and southern Japan, Alaska, and Cascadia. The differences in earthquake depth relative to subducting crust may reflect large differences in temperature and thus locations of major dehydration reactions. In colder slabs, the crust passes through blueschist-facies dehydration reactions, while in Cascadia and Nankai the major dehydration reactions in crust may be due to zoisite- and amphibole-breakdown or associated melting. The cold paths allow more mineral-bound H2O to be retained within the crust at shallow depths, eventually released upon dehydration over shorter time intervals than warm paths. The cold path dehydration reactions also result in net positive volume changes of solid+fluid, with solid volume decreasing less than the volume of H2O produced. On hot paths the net volume changes are negative, with solid volumes decreasing more than the volume of H2O produced. The difference in behavior could drive a net increase in pore pressure upon dehydration for the cold but not the hot crustal paths. The difference in rate of release in H2O, and difference in sign of net system volume change may promote seismogenesis in cold subduction zones but inhibit it in the crust of warm slabs. Within the mantle of the downgoing plate earthquakes mostly occur where serpentine is stable or breaks down, in both settings.
AB - We find that in young and warm subducting plates, earthquakes occur just below the Moho. In older plates, earthquakes occur throughout the subducting oceanic crust, as well as the subducting mantle. We document this behavior in several subduction zones where there are independent constraints on earthquake locations and slab structure, specifically for northern and southern Japan, Alaska, and Cascadia. The differences in earthquake depth relative to subducting crust may reflect large differences in temperature and thus locations of major dehydration reactions. In colder slabs, the crust passes through blueschist-facies dehydration reactions, while in Cascadia and Nankai the major dehydration reactions in crust may be due to zoisite- and amphibole-breakdown or associated melting. The cold paths allow more mineral-bound H2O to be retained within the crust at shallow depths, eventually released upon dehydration over shorter time intervals than warm paths. The cold path dehydration reactions also result in net positive volume changes of solid+fluid, with solid volume decreasing less than the volume of H2O produced. On hot paths the net volume changes are negative, with solid volumes decreasing more than the volume of H2O produced. The difference in behavior could drive a net increase in pore pressure upon dehydration for the cold but not the hot crustal paths. The difference in rate of release in H2O, and difference in sign of net system volume change may promote seismogenesis in cold subduction zones but inhibit it in the crust of warm slabs. Within the mantle of the downgoing plate earthquakes mostly occur where serpentine is stable or breaks down, in both settings.
KW - Intermediate-depth earthquakes
KW - Metamorphic devolatilization
KW - Subduction
KW - Thermal models
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U2 - 10.1016/j.epsl.2013.03.022
DO - 10.1016/j.epsl.2013.03.022
M3 - Article
AN - SCOPUS:84878177231
VL - 369-370
SP - 178
EP - 187
JO - Earth and Planetary Sciences Letters
JF - Earth and Planetary Sciences Letters
SN - 0012-821X
ER -