Seismicity in ocean ridge-transform systems reveals fundamental processes of mid-ocean ridges, while comparisons of seismicity in different oceans remain rare due to a lack of detection of small events. From 1996 to 2003, the Pacific Marine Environmental Laboratory of the National Oceanic and Atmospheric Administration (NOAA/PMEL) deployed several hydrophones in the eastern Pacific Ocean and the northern Atlantic Ocean. These hydrophones recorded earthquakes with small magnitudes, providing us with opportunities to study the seismic characteristics of ridge-transform systems at different spreading rates and make further comparisons of their differences. This study comparatively analyzed hydroacoustic and teleseismic data recorded on the fast-spreading East Pacific Rise (EPR, 10°S to 12°N), intermediate-spreading Galapagos Ridge (103° W to 80° W), and slow-spreading Mid-Atlantic Ridge (MAR, 15°N to 37°N). We present a systematic study of the spatial and temporal distribution of events, aftershock seismicity, and possible triggering mechanisms of aftershock sequences. Our analysis yields the following conclusions. (1) From the hydroacoustic data, the EPR transform faults had the highest average seismicity rate among the three regions. (2) Along-ridge event distributions show that a high number of earthquakes were concentrated on the EPR, while they became dispersed on the GR and fewer and more scattered on the MAR, reflecting that the different tectonic origins were closely correlated with the spreading rate. (3) Analysis from mainshock-aftershock sequences shows no significant differences in the aftershock decay rate among the three regions. (4) Multiple types of aftershock triggering models were inferred from Coulomb stress changes: strike-slip mainshocks triggered strike-slip aftershocks and normal faulting aftershocks, and normal faulting mainshocks triggered normal faulting aftershocks. Although these results are case studies, they may be applicable to other ocean ridge-transform systems in future investigations. Our results provide important new insights into the seismicity of global ocean ridge-transform systems.

Tingting Zheng;Jian Lin;Qiu Zhong

Key Laboratory of Ocean and Marginal Sea Geology,South China Sea Institute of Oceanology,Innovation Academy of South China Sea Ecology and Environmental Engineering,Chinese Academy of Sciences,Guangzhou 510301,China;Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou),Guangzhou 511458,China;China-Pakistan Joint Research Center on Earth Sciences,Chinese Academy of Science–Higher Education Commission(Pakistan),Islamabad 45320,Pakistan;Department of Ocean Science and Engineering,Southern University of Science and Technology,Shenzhen 518055,China;Department of Geology and Geophysics,Woods Hole Oceanographic Institution,Woods Hole,MA 02543,USA

海洋学报（英文版）

[1]Tingting Zheng;Jian Lin;Qiu Zhong-.Spreading-rate dependence of hydroacoustic and teleseismic seismicity of ridge-transform systems: East Pacific Rise, Galapagos Ridge, and Mid-Atlantic Ridge)[J].海洋学报（英文版）,2022(05):124-135,中插5-中插56

hydroacoustic,mainshocks

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