Seismic activity recorded by a single OBS/H near the active Longqi hydrothermal vent at the ultraslow spreading Southwest Indian Ridge (49°39′ E) |
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| Authors: | Yunlong Liu Cai Liu Lei Qiu Vera Schlindwein Haijiang Zhang |
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| Institution: | 1. College of Geoexploration Science and Technology, Jilin University, Changchun, China;2. Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, State Oceanic Administration, Hangzhou, China;3. Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, State Oceanic Administration, Hangzhou, China;4. Helmholtz Centre for Polar and Marine Research, Alfred Wegener Institute, Bremerhaven, Germany;5. Laboratory of Seismology and Physics of Earth’s Interior, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, China |
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| Abstract: | ABSTRACTIn this paper, we describe the results of a first pilot experiment of passive seismic monitoring near the active Longqi hydrothermal vent at the Southwest Indian Ridge during Chinese cruise DY115-30. During 102-day experiment, we recorded over 2,000 seismic events on a single ocean bottom seismometer with hydrophone close to the hydrothermal field. We classified these events into the following three classes based on their time–frequency characteristics: (1) volcano tectonic microearthquakes (VTMs); (2) regional earthquakes; (3) short-duration events (SDEs). We preliminarily located the 1,277 VTMs using a single-station location method. Our results revealed hypocenters primarily beneath the axial valley ridge which is about 10?km away from hydrothermal vent and extending to the upper mantle at a depth of 15?km. Two discrete swarms of VTMs occurred during our survey period. The SDEs show a complex frequency characteristics ascribed to clusters of monochromatic waves around different frequencies. This suggests that SDEs result from combination of harmonic waves resonating in fluid-filled pipes and cracks. |
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| Keywords: | Hydrothermal circulation microearthquake OBS short-duration event |
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