Relationship between coseismic ground deformation and geological structures associated with the 2016 Mw 6.5 central Italy earthquake

Abstract

<p>In the last three decades, remote sensing techniques, such as Differential Synthetic Aperture Radar Interferometry (DInSAR), have been exploited for investigating, with high accuracy, ground displacement phenomena. Large seismic events can trigger deformations at the surface, which are controlled by the active faults and the intercepted lithologies.<br />In 2016-2017, a long earthquake sequence struck the Apennines in central Italy, producing impressive surface ruptures attributed to the 24 August Mw 6.0 and 30 October Mw 6.5 mainshocks. These ruptures were investigated and mapped by field geologists soon after the earthquakes, and during the following years also by remote sensing data.</p> <p>We present detailed maps of the surface deformation pattern produced by the M. Vettore Fault System (VFS) during the October 2016 earthquakes. The DInSAR analysis has been retrieved from ALOS-2 SAR data, via the Parallel Small BAseline Subsets (P-SBAS) algorithm. At the local scale, we identify a large number of surface ruptures, most of which already observed in the field. At the large scale, we trace a set of five geological cross-sections to inspect a possible link between the coseismic vertical displacement, the lithology distribution and the tectonic structures of the area (i.e., thrusts, normal faults). On these sections, we also project the seismicity distribution recorded during October 2016.</p> <p>The integration of such datasets allows the recognition of an important geological control in the overall distribution of the deformation, which shows maximum values in correspondence of the carbonatic multilayer and minimum values within the clastic succession. The distribution of seismicity allows also us to distinguish seismogenic by aseismic slip associated with fault ruptures.</p> <p>Along the sections, we observe a typical long-wavelength convex curvature of the subsiding block, not directly recognizable in the field.  In the area of maximum subsidence, this curvature is interrupted by an anthitetic fault at which is not associated with any seismicity. In addition, we observe that further deformation is localized at the footwall of the VFS, corresponding to the hangingwall block of an important thrust fault, where shallow seismicity was also recorded. Here, we observe that the coseismic deformation tends to decrease toward the outcropping thrust. In the south sector, instead, we do not observe a control of regional thrusts acting as a barrier to the deformation.</p> <p>The results of this work demonstrate that the integration of surface geology, remote sensing data and seismicity, can lead to a better understanding of the influence of geological structures on the distribution of the surface deformation associated with earthquakes.</p>