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Seismic image and its implications for an earthquake swarm at an active volcanic region off the Miyake‐jima–Kozu‐shima, Japan
Author(s) -
Kodaira Shuichi,
Uhira Kohichi,
Tsuru Tetsuro,
Sugioka Hiroko,
Suyehiro Kiyoshi,
Kaneda Yoshiyuki
Publication year - 2002
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2001gl014377
Subject(s) - earthquake swarm , swarm behaviour , seismology , geology , volcano , geodetic datum , reflector (photography) , geophysical imaging , earthquake location , reflection (computer programming) , geophysics , geodesy , induced seismicity , optics , physics , mathematical optimization , mathematics , light source , computer science , programming language
An intensive earthquake swarm, which is proposed to be attributed to the magmatic activity, has continued in more than six months around the Miyake‐jima–Kozu‐shima. A wide‐angle seismic survey was conducted immediately above the swarm. The purpose of this study is to map the seismic velocity structure of the swarm area, and to investigate structural evidence indicating magmatic activity. From the result of first arrival refraction tomography, we found a 5–8% decrease in P‐wave velocity surrounding the swarm. A depth migration of the intra‐crustal reflection phase also shows an existence of a reflector immediately below the swarm (10–13 km depth). Compared with the seismic imaging, geodetic data and earthquake focal mechanisms, the intra‐crustal reflector we found might be the top of magmatic body which has caused the earthquake swarm between Miyake‐jima and Kozu‐shima.