ABSTRACT We present the results of a paleoseismic study of the Akatore Fault in the low seismicity region of Otago, New Zealand. Two trenches reveal at least three reverse fault ruptures that are constrained to have occurred between 13,314 B.C. and 680 A.D. (antepenultimate event), 737 and 960 A.D. (penultimate event) and 1047 and 1278 A.D. (most recent event), with a single-event displacements of 1.6–2.5 m. Ground Penetrating Radar (GPR) profiles and sediment analyses show that a 125 ka marine terrace is likely also only displaced by these three events, suggesting these earthquakes have ended a minimum 110,000 year period of quiescence on the fault. The fault therefore appears to exhibit strong aperiodicity of earthquake occurrence, a characteristic previously suggested for the Akatore Fault and other well-studied Otago faults. Slip rate and recurrence interval for the current active period are 0.3–6.0 mm/yr and 450–5110 years respectively. We suggest that for seismic hazard assessments in nearby Dunedin it is prudent to assume that the high rates of recent earthquakes will continue into the immediate future on the Akatore Fault.

中文翻译：

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新西兰奥塔哥 Akatore 断层的古地震学

摘要 我们介绍了新西兰奥塔哥低地震活动区 Akatore 断层的古地震研究结果。两条海沟揭示了至少三个反向断层破裂，这些破裂被限制发生在公元前 13,314 年和公元 680 年（倒数第二个事件）、公元 737 年和 960 年（倒数第二个事件）以及公元 1047 年和 1278 年（最近的事件）之间，有一个单一事件1.6-2.5 m 的位移。探地雷达 (GPR) 剖面和沉积物分析表明，一个 125 ka 的海洋阶地也可能仅被这三个事件所取代，这表明这些地震已经结束了断层上至少 110,000 年的静止期。因此，该断层似乎表现出强烈的地震发生的非周期性，这是先前建议的 Akatore 断层和其他经过充分研究的奥塔哥断层的特征。当前活动期的滑移率和复发间隔分别为 0.3-6.0 毫米/年和 450-5110 年。我们建议，对于附近但尼丁的地震危险性评估，谨慎地假设阿卡托雷断层最近的高地震率将持续到不久的将来。