TY - JOUR T1 - Spatial variations in the frequency-magnitude distribution of earthquakes in the southwestern Okinawa Trough A1 - Lin,Jing-Yi A1 - Sibuet,Jean-Claude A1 - Lee,Chao-Shing A1 - Hsu,Shu-Kun A1 - Klingelhoefer,Frauke AD - IFREMER, Ctr Brest, F-29280 Plouzane, France. AD - Natl Taiwan Ocean Univ, Inst Appl Geophys, Chilung 202, Taiwan. AD - Natl Cent Univ, Inst Geophys, Chungli 32001, Taiwan. AD - Coll France, Chaire Geodynam, F-13545 Aix En Provence 4, France. UR - https://archimer.ifremer.fr/doc/00000/3036/ KW - Magma chamber KW - Slab tear KW - Southern Okinawa Trough backarc basin KW - B Values N2 - The relations between the frequency of occurrence and the magnitude of earthquakes are established in the southern Okinawa Trough for 2823 relocated earthquakes recorded during a passive ocean bottom seismometer experiment. Three high b-values areas are identified: (1) for an area offshore of the Ilan Plain, south of the andesitic Kueishantao Island from a depth of 50 km to the surface, thereby confirming the subduction component of the island andesites; (2) for a body lying along the 123.3 degrees E meridian at depths ranging from 0 to 50 km that may reflect the high temperature inflow rising up from a slab tear; (3) for a third cylindrical body about 15 km in diameter beneath the Cross Backarc Volcanic Trail, at depths ranging from 0 to 15 km. This anomaly might be related to the presence of a magma chamber at the base of the crust already evidenced by tomographic and geochemical results. The high b-values are generally linked to magmatic and geothermal activities, although most of the seismicity is linked to normal faulting processes in the southern Okinawa Trough. Y1 - 2007/05 PB - TERRAPUB JF - Earth, Planets and Space SN - 1343-8832 VL - 59 IS - 4 SP - 221 EP - 225 ID - 3036 ER -