Earthquake surface ruptures on the altiplano and geomorphological evidence of normal faulting in the December 2016 (Mw 6.1) Parina earthquake, Peru
Earthquake surface ruptures on the altiplano and geomorphological evidence of normal faulting in the December 2016 (Mw 6.1) Parina earthquake, Peru
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DOI：
10.1016/j.jsames.2020.103098
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发表时间：
2021-03-01
影响因子：
1.8
通讯作者：
Palomino, Anderson
中科院分区：
文献类型：
--
作者：
Aguirre, Enoch;Benavente, Carlos;Palomino, Anderson
2016年发生的6.1兆瓦帕里纳地震破裂了秘鲁南部安第斯高地内的一条浅层地壳正断层。我们使用高分辨率DEM和地震产生的地表破裂的现场制图，结合同震和震后InSAR测量，研究了Parina断层上的地震旋回如何产生Parina地貌的不同特征。我们系统地绘制了12公里的NW-SE走向的地表破裂图，垂直位移高达27厘米，沿走向的张开度类似于25厘米，由一个空隙隔开，没有明显的地表破裂。同震和震后InSAR测量需要滑动到地表破裂的这个缺口以下，这意味着在古地震沟中观察到的地表偏移量不一定代表孕震深度的滑动，通常会低估古地震的震级。地表破裂沿10-20m高的累积陡坎发育，穿过晚第四纪河流-冰川沉积和基岩。2016年的帕里纳地震并没有使第四纪晚期的陡坎全长断裂，这意味着帕里纳断层在特征上不会滑动，重复地震。在帕里纳和秘鲁高原的大部分地区，正常断层最容易从最近切割第四纪晚期冰川峰顶的陡坎中辨认出来。在没有新近沉积的冰雹的地区，断层很难识别，而且缺乏量化断层滑动速率的时间限制。出于这个原因，目前的断层图可能低估了高原的地震危险性。
The 2016 Mw 6.1 Parina earthquake ruptured a shallow-crustal normal fault within the high Andes of south Peru. We use high-resolution DEMs and field mapping of the surface ruptures generated by the earthquake, in combination with co-seismic and post-seismic InSAR measurements, to investigate how different features of the geomorphology at Parina are generated by the earthquake cycle on the Parina Fault. We systematically mapped 12 km of NW-SE trending surface ruptures with up to similar to 27 cm vertical displacement and similar to 25 cm tensional opening along strike, separated by a gap with no observable surface ruptures. Co- and post-seismic InSAR measurements require slip below this gap in surface ruptures, implying that surface offsets observed in paleoseismic trenches may not necessarily be representative of slip at seismogenic depths, and will typically yield an underestimate of paleo-earthquake magnitudes. The surface ruptures developed along 10-20 m high cumulative scarps cutting through late Quaternary fluvio-glacial deposits and bedrock. The 2016 Parina earthquake did not rupture the full length of the late Quaternary scarps, implying that the Parina Fault does not slip in characteristic, repeat earthquakes. At Parina, and across most of the Peruvian Altiplano, normal faults are most-easily identified from recent scarps cutting late Quaternary moraine crests. In regions where there are no recently-deposited moraines, faults are difficult to identify and lack time constraints to quantify rates of fault slip. For this reason, current fault maps may underestimate the seismic hazard in the Altiplano.