An analysis of earthquakes recorded in southern New Caledonia (SNC) over 14 months during 2018–2019 reveals focal mechanisms consistent with a normal‐faulting stress state. The minimum principal stress is perpendicular to the Vanuatu subduction zone (VSZ), which is 200 km away, and is highly oblique to the local topographic ridge of New Caledonia, which may induce additional tension. An Mw 7.5 earthquake occurred in VSZ on 5 December 2018, and focal mechanisms appear to be different to those before the big earthquake. Significant increase in seismicity rates in both VSZ and SNC are observed following this large earthquake. A strong correlation between local and subduction zone seismicity rates is confirmed by analyses of seismic records before and after large subduction zone earthquakes 200–350 km away during the period of 2000–2018. The local seismicity rate and seismic hazard in SNC is about four times higher immediately after a large subduction earthquake, and Omori decay returns it to background levels after about 30 days. The triggering mechanisms remains unclear, but our study provides the first observations and a framework for future work.

中文翻译：

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新喀里多尼亚南部瓦努阿图俯冲带外隆起的应力状态和地震触发

对 2018 年至 2019 年期间 14 个月内新喀里多尼亚南部 (SNC) 记录的地震的分析揭示了与正断层应力状态一致的震源机制。最小主应力垂直于200公里外的瓦努阿图俯冲带（VSZ），并且与新喀里多尼亚当地地形脊高度倾斜，这可能会引起额外的张力。 2018年12月5日，VSZ发生了7.5级地震，震源机制似乎与大地震前有所不同。这次大地震后，VSZ 和 SNC 的地震活动率显着增加。通过对2000-2018年期间200-350公里外俯冲带大地震前后的地震记录分析，证实了当地和俯冲带地震活动率之间存在很强的相关性。大俯冲地震发生后，SNC 的当地地震活动率和地震危险性大约高出四倍，大森衰变在大约 30 天后将其恢复到背景水平。触发机制尚不清楚，但我们的研究提供了初步观察结果和未来工作的框架。