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 < 50–100) directly above the shallow slow slip event of 2014–2015, beneath the offshore seismic array. This highest attenuation is downdip of a subducting seamount, and is spatially correlated with a high seismic reflectivity zone and Vp/Vs > 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.

中文翻译：

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新西兰北岛海库兰吉俯冲带北部近海沟3D地震衰减附近

我们使用海底和陆基地震仪对新西兰离岸希库朗吉海沟附近的地震衰减进行成像，揭示了在反复发生的浅层缓滑事件上方和俯冲希库朗吉高原内的高衰减。新西兰北岛以东的Hikurangi俯冲带是频繁的浅层缓慢滑动事件的发源地。据推测，超压流体会导致在靠近海沟的浅层深度缓慢滑动。地震衰减，地震波的能量损失可用于检测高温，融化，流体的存在和裂缝。我们使用来自180次地震的本地地震P波和S波对t进行反演*，随后将Qp和Qs反转，在慢滑区域正上方的北岛海上。我们将Qp和Qs成像到约25 km的深度，从而提高了先前确定的沿海低Q的分辨率（100–300），并在2014–2015浅层缓慢滑动事件的正上方，离岸地震台阵下方，找到一个更高衰减的新区域（Qp和Qs <50–100）。该最大衰减是俯冲海山的下倾角，并且在空间上与高地震反射率区域和Vp / Vs> 1.85相关，所有这些都为流体的存在提供了证据。在海沟（<50–100）和俯冲板（100–200），Qp和Qs较低，这表明由于Hikurangi高原（大火成岩）的断层，裂缝和固有的非均质成分而引起的地震波散射省，在地震衰减中发挥作用。