A photographic collection of the coseismic geological effects induced by the 21 August 2017, M=4, Casamicciola earthquake (Ischia island, Italy)

Abstract

On 21 August 2017, a shallow earthquake of Md 4.0 struck the Casamicciola Terme village in the north of Ischia volcanic island (Italy). The earthquake has the typical characteristics of volcano­ tectonic events recorded at active volcanoes and occurred along the E­W normal system fault bounding the northern slope of Mt. Epomeo. The epicentral area has been repeatedly damaged in the last three centuries (1796, 1828, 1881, 1883) [Alessio et al., 1996; Carlino et al., 2011; Cubellis and Luongo, 1998]. In this work, we present a collection of pictures showing the geological effects produced on either the natural or the built environment by the Casamicciola earthquake. Most of the coseismic geologic effects were observed along the E­W piedmont belt of Mt. Epomeo, which extends for about 2 km between the village of Fango (Lacco Ameno) to the west and Bagni Square to the East (Fig. 1). Mapped effects define a belt which closely follows the trace of the Casamicciola E­W trending normal fault system, bounding the northern slope of Mt. Epomeo, previously known as a Latest Pleistocene to Holocene normal fault [Nappi et al., 2018]. The Emergeo Working Group conducted a field work, collecting data that were managed following the procedures codified after the earthquake sequences of Emilia 2012 and Amatrice­Visso­Norcia 2016­2017 [Emergeo Working Group, 2012, 2016; Pucci et al., 2017; Civico et al., 2018; Villani et al., 2018]. Photographic collections of the coseismic geological effects induced by these earthquake were also published [Emergeo Working Group, 2012; Emergeo Working Group, 2017 a, b]. Field measurements were greatly aided by the use of mobile devices equipped with a specific software employing GPS, compass and orientation sensors (Rocklogger© mobile app, www.rockgecko.com), which allowed for quick and accurate structural data collection and real­time sharing. The whole data set was stored and managed in a georeferenced database on an Environmental Systems Research Institute ArcGIS platform. Further data were acquired using remotely piloted aircraft systems (RPAS) equipped with a Sony Alpha 6000 camera and a Flir SC655 thermal camera. We collected more than 100 observations of several different coseismic effects across the epicentral area and its sourroundings. These include fractures, ruptures, and a few minor gravitational phenomena like collapses and small landslides in volcanoclastic deposits. Moreover we observed widespread effects related to shaking, such as...