Quantifying seismic induced damage at ancient site Manjal located in Kachchh Mainland region of Gujarat, India

Abstract

Kachchh of western India, considered to be a Stable Continental Region (SCR), has experienced several large magnitude earthquakes in recent past, viz. 1668 CE (Mw7.0), 1819 CE (Mw7.8), 1845 CE (Mw6.3), 1956 CE (Mw6.0), and 2001 CE (Mw7.7). Our present study emphasizes on identifying archaeoseismic signatures from the ruins of an ancient city built by Lakho Punarvo of Samma Dynasty around 1000 CE found near the Manjal Town of Kachchh. Among the ruins, Punvareshwar Temple exhibits penetrative fractures within masonry blocks, recycled anomalous elements, displaced blocks and lateral shift of superstructure. Vadi Medi, a pillared structure, shown varied orientation of intact columns, displaced blocks, fallen and oriented columns. The nature of these signatures exhibits the influence of seismic phenomena which can be categorized as off-fault damage caused by strong seismic shaking. In order to quantify the ground shaking experienced by the structures, seismic hazard analysis which considers all the possible potential seismic sources within a radius of 100 km has been employed. It is identified from the analysis that the damage incurred to the structures is due to the strong ground acceleration experienced during the 1819 and 2001 earthquakes and the recurrence of similar peak ground acceleration is estimated as 700–750 and 500–600 years respectively.