Comparison of Earthquake Environmental Effects and ESI intensities for recent seismic events in different tectonic settings: Sichuan (SW China) and Central Apennines (Italy)

Abstract

Abstract In the framework of a bilateral cooperation project between the geological surveys of China and Italy, the geological effects of six strong to moderate earthquakes occurred in Sichuan, China (2008, 2013, 2017) and in Central Apennines, Italy (2009, 24 Aug. and 30 Oct 2016) were compared. The main aim was to test the applicability and effectiveness of the ESI intensity scale in areas characterized by different tectonic settings (compressive and strike-slip vs. extensional), and also by different local conditions (e.g., geomorphologic, lithologic and climatic) that can influence the occurrence and size of individual EEEs at a specific site. In general, for all these earthquakes the distribution and size of geological effects resulted proportional to the earthquake severity. However, notably, the earthquakes of moderate magnitude (i.e., between 6 and 7) showed i) well evident surface faulting only in the extensional domain of the Central Apennines, while poor or no evidence was found for reverse and strike-slip events (Sichuan); ii) a strong influence on the occurrence of secondary effects from site conditions (e.g., lithology, elevation, slope angle, soil cover, climate), those that typically control for example the susceptibility to landsliding. Based on the ESI intensity scale, epicentral and local intensities were estimated by means of the surface faulting extent and of the total area of secondary effects, mainly landslides. The comparison with the damage or PGA-based intensities has confirmed the efficacy of the ESI scale to improve the portrait of the earthquake and to pinpoint areas of enhanced hazard, especially those related to slope failures and liquefaction. This work is also a substantial contribution to the future revision of the ESI scale, in particular for reverse faulting earthquakes.