Investigating source directivity of moderate earthquakes by multiple approach: the 2013 Matese (southern Italy)Mw = 5 event

Abstract

Preferential direction in rupture propagation of earthquakes is known to have strong consequences on the azimuthal distribution of the ground motion. While source directivity effects are well established for large seismic events, their observation for moderate and small earthquakes are still restricted to a few cases. This is mainly due to intrinsic difficulties in recognizing source directivity unambiguously for less energetic/shorter ruptures. Therefore, we propose the use of multiapproach analysis for revealing the possible directivity for small-to-moderate earthquakes, taking advantage of the different sensitivity of each approach to various source and propagation characteristics. Here, we demonstrate that the application of six diverse and independent methods converges in giving consistent information on the rupture kinematics of the 2013 December 29, Mw = 5.0 earthquake. The results indicate a distinct rupture propagation direction toward S-SW, which correlates with observed asymmetry of damage and felt area. Overall, we conclude that the use of a single technique cannot provide a univocal solution, whereas the application of distinct analyses helps to strongly constrain source kinematics and should be preferred, in particular when dealing with small-to-moderate earthquakes.