Map of the seismicity of the region from 1985 to today: in blue the epicenters from 1985 to July 2016, in yellow the epicenters from 24 August to 25 October 2016, in red those from 26 October to 3 November 2016. The stars are the magnitude events equal to or greater than 5.0.
The report describes: the analysis of seismological data, with maps and vertical sections through the epicentral area; the fault models based on seismometric and accelerometric data, on geodetic data (GPS and SAR - satellite radar interferometry) with the first indications of the distribution of the detailed movement of the various faults; the impact of the earthquake on the territory, "seen" by seismic data and estimated on the basis of shake maps and field analyses; faulting, observed on the surface throughout the area affected by the strongest earthquakes from August 24 to October 30; and, finally, an estimate of the probability of occurrence of future aftershocks.
Map of GPS co-seismic displacements – horizontal (red arrows) and vertical (blue arrows) – obtained from the combination of three independent geodetic solutions for the October 30, 2016 event. The white squares show the position of the permanent GPS stations and the colored ones magenta of the RING-INGV stations (doi:10.13127/RING). The orange squares show the permanent GPS stations managed by DPC and ISPRA. The green and blue squares show the stations of the CaGeoNet network and the IGM network, respectively, re-occupied after August 24th.
From the analysis of all the data analyzed so far, interesting results are emerging on the fault system that crosses the region and which has been activated in this seismic sequence which, we recall, is still ongoing. In fact, there are still several hundred replicas that are located every day by the INGV National Seismic Network.
The analysis of the geological, geodetic and seismological data are consistent in the identification of the faults and their kinematics, although some elements have been observed which are being investigated and which are the symptom of the complexity of the system.
However, it is now clear that the faults responsible for the earthquakes are those known in the literature as the Monte Vettore-Bove fault, normal faults (ie extensional faults) oriented in the NNW-SSE direction and dipping towards the west. The faults were activated along the entire thickness of the seismogenic layer, from a depth of about 10 km to the surface, producing clearly visible breaks on the outcrop, with "disputations" (ie steps) reaching two meters in some points.
Co-seismic rupture of 30 October 2016: dislocation along the rock fault plane.
These ruptures observed on the surface represent the continuation of the deep movement on the fault plane, which originated around 8-10 km (the hypocenter) and propagated laterally and upwards. Both the accelerometric and geodetic data are consistent in identifying the zones of maximum displacement of the 30 October fault, which is located between the previous ruptures of 24 August in the south and 26 October in the north, mainly affecting the central sector of the faults and its most superficial part, where displacements exceeding 2.5 meters on the fault plane are identified. It is in fact evident that the displacement along the various fault segments active in recent months has not occurred in a homogeneous manner, but has had strong heterogeneity: displacements from a few decimeters to 1-2 meters on the plane of the same fault. This could explain the complexity of the sequence, with the successive activation of fault segments of different sizes and with very different displacements of the two edges of the fault. Also visible are other "minor" faults that moved during the sequence.
Preliminary model of the seismic source of the October 30 earthquake obtained from InSAR data.
More refined models are being developed to identify the details of this geometry and kinematics by jointly comparing and analyzing all available data.
The analysis of the accelerometric data from the earthquake of 30 October in Amatrice, where a temporary seismic network had been installed to carry out preparatory investigations for seismic micro-zoning activities, highlighted strong variations in ground accelerations at very short distances, with amplifications up to a factor of 5 compared to rock sites, mainly due to the geological surface structure.
Z component of the accelerations recorded in the town of Amatrice – San Cipriano during the Mw 6.5 earthquake of 30 October 2016; for each station the vertical PGA values are also indicated.
The analyzes continue to closely follow the trend of the replicas (the number of which has now exceeded 26000), for a detailed mapping of the surface effects, to create fault models that are able to take into account all the elements observed on the ground and from the satellite.
The complete report is available at the following link "SUMMARY REPORT ON THE EARTHQUAKE IN CENTRAL ITALY MW 6.5 OF OCTOBER 30, 2016" by the INGV Working Group on the earthquake in central Italy (2016).
Cite as: INGV Working Group on the earthquake in central Italy (2016). Summary report on the earthquake in central Italy Mw 6.5 of 30 October 2016, doi: 10.5281/zenodo.166019