Abstract

Slow slip events (SSEs) are interpreted as the transient quasi-static fault deformation in the deep transition zone from locked to freely slipping in many subduction zones. Using continuous Global Positioning System (cGPS) data collected in New Zealand, we estimate the spatiotemporal evolution model during the 2019 SSE and analyze the influence of subduction interface heterogeneity on seismicity during SSEs at the Hikurangi margin. The results reveal that the 2019 SSE extends from the northern (Gisborne) to the central (Hawke’s Bay) Hikurangi subduction interface and decays rapidly within approximately 3-4 weeks. It releases a total seismic moment of about 4.83 × 10¹⁹ N·m (Mw 6.8), with a significant slip in Gisborne and a secondary slip in Hawke’s Bay. The slip depths are similar, but peaks, durations, and rates differ slightly. By combining previous SSEs (2011-2019), diverse characteristics are concluded, i.e., shorter duration and more frequency in Gisborne and relatively longer duration and less frequency in Hawke’s Bay. The seismicity offshore and onshore indicates along-strike variations, which appear to be spatially correlated with the variations in topography, such as subduction seamounts. The heterogeneities on the subduction interface are related to the spatiotemporal distribution of SSEs and seismicity along the Hikurangi margin.

摘要

慢滑移事件 (SSE) 被解释为在许多俯冲带中从锁定到自由滑移的深层过渡带中的瞬时准静态断层变形。利用在新西兰收集的连续全球定位系统 (cGPS) 数据，我们估计了 2019 年 SSE 期间的时空演化模型，并分析了俯冲界面异质性对 Hikurangi 边缘 SSE 期间地震活动的影响。结果显示，2019 年 SSE 从北部（吉斯本）延伸到中部（霍克斯湾）Hikurangi 俯冲界面，并在大约 3-4 周内迅速衰减。它释放的总地震力矩约为 4.83 × 10 ¹⁹N·m (Mw 6.8)，在 Gisborne 发生明显滑移，在 Hawke's Bay 发生二次滑移。滑动深度相似，但峰值、持续时间和速率略有不同。通过结合以往的 SSE（2011-2019），得出了不同的特征，即 Gisborne 持续时间较短且频率较高，而 Hawke's Bay 持续时间相对较长且频率较低。近海和陆上地震活动表明沿走向变化，这似乎在空间上与地形变化相关，例如俯冲海山。俯冲界面的非均质性与 SSE 的时空分布和沿 Hikurangi 边缘的地震活动有关。