Near Trench 3D Seismic Attenuation Offshore Northern Hikurangi Subduction Margin, North Island, New Zealand
Near Trench 3D Seismic Attenuation Offshore Northern Hikurangi Subduction Margin, North Island, New Zealand
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DOI：
10.1029/2020jb020810
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发表时间：
2021-02
期刊：
影响因子：
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通讯作者：
J. Nakai;A. Sheehan;R. Abercrombie;D. Eberhart‐Phillips
中科院分区：
文献类型：
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作者：
J. Nakai;A. Sheehan;R. Abercrombie;D. Eberhart‐Phillips
我们使用海底和陆基地震仪对新西兰近海Hikurangi海沟附近的地震衰减进行了成像，揭示了在反复发生的浅层慢滑事件上方和俯冲的Hikurangi高原内的高衰减。新西兰北岛东部的希库朗吉俯冲边缘是频繁发生浅慢滑动事件的地点。超压流体被假设为导致在靠近海沟的浅深度处的缓慢滑动。地震衰减，地震波的能量损失，可用于检测高温，熔融，流体的存在和裂缝。我们使用来自180次地震的当地地震P波和S波来反演t*，随后反演Qp和Qs，北岛近海正上方的缓慢滑动区域。我们对Qp和Qs进行了成像，深度为1.25 km，提高了先前确定的沿海低Q（100-300）的分辨率，并发现了一个衰减更高的新区域（Qp和Qs 1.85），所有这些都为流体的存在提供了证据。海沟（<50-100）和俯冲板块（100-200）的Qp和Qs较低，表明断层、裂缝和希库朗吉高原（一个大火成岩省）固有的不均匀成分造成的地震波散射在地震衰减中起作用。
We image seismic attenuation near the Hikurangi trench offshore New Zealand, using ocean bottom and land‐based seismometers, revealing high attenuation above a recurring shallow slow‐slip event and within the subducting Hikurangi Plateau. The Hikurangi subduction margin east of the North Island, New Zealand is the site of frequent shallow slow slip events. Overpressured fluids are hypothesized to lead to slow slip at shallow depths close to the oceanic trench. Seismic attenuation, energy loss of seismic waves, can be used to detect high temperatures, melt, the presence of fluids, and fractures. We use local earthquake P‐ and S‐waves from 180 earthquakes to invert for t*, and subsequently invert for Qp and Qs, offshore the North Island directly above the area of slow slip. We image Qp and Qs to ∼25 km depth, increasing resolution of previously identified coastal low Q (100–300), and finding a new region of even higher attenuation (Qp and Qs 1.85, all of which provide evidence for the presence of fluids. The Qp and Qs is low at the trench (<50–100) and in the subducting plate (100–200), suggesting that seismic wave scattering due to faults, fractures, and the inherent heterogeneous composition of the Hikurangi Plateau, a large igneous province, plays a role in seismic attenuation.