Bignami Christian, Valerio Emanuela, Carminati Eugenio, Doglioni Carlo, Tizzani Pietro, Lanari Riccardo
Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy.
Dipartimento di Scienze della Terra, Sapienza University, Rome, Italy.
Sci Rep. 2019 Mar 12;9(1):4250. doi: 10.1038/s41598-019-40958-z.
We analyse the M 6.5, 2016 Amatrice-Norcia (Central Italy) seismic sequence by means of InSAR, GPS, seismological and geologic data. The >1000 km area affected by deformation is involving a volume of about 6000 km and the relocated seismicity is widely distributed in the hangingwall of the master fault system and the conjugate antithetic faults. Noteworthy, the coseismically subsided hangingwall volume is about 0.12 km, whereas the uplifted adjacent volumes uplifted only 0.016 km. Therefore, the subsided volume was about 7.5 times larger than the uplifted one. The coseismic motion requires equivalent volume at depth absorbing the hangingwall downward movement. This unbalance regularly occurs in normal fault-related earthquakes and can be inferred as a significant contribution to coseismic strain accomodated by a stress-drop driven collapse of precursory dilatancy. The vertical coseismic displacement is in fact larger than the horizontal component, consistent with the vertical orientation of the maximum lithostatic stress tensor.
我们借助合成孔径雷达干涉测量（InSAR）、全球定位系统（GPS）、地震学和地质数据，对2016年意大利中部阿马特里切-诺尔恰6.5级地震序列进行了分析。受变形影响的区域超过1000公里，涉及的体积约为6000立方公里，重新定位的地震活动广泛分布在主断层系统的上盘和共轭反向断层中。值得注意的是，同震下沉的上盘体积约为0.12立方公里，而相邻隆起的体积仅隆起了0.016立方公里。因此，下沉体积大约是隆起体积的7.5倍。同震运动需要在深度上有等量的体积来吸收上盘的向下运动。这种不平衡在与正断层相关的地震中经常出现，可以推断这是由前兆扩容的应力降驱动坍塌所导致的同震应变调节的一个重要因素。事实上，垂直同震位移大于水平分量，这与最大岩石静压力张量的垂直方向一致。
