Historical Constraints on Previous Seismic Activity and Morphologic Changes near the Source Zone of the 1819 Rann of Kachchh Earthquake: Further Light on the Penultimate Event

Abstract

The Kachchh (also spelled Kutch and Cutch) province in the northwestern part of India continues to be remarkably active seismically, the 2001 Bhuj ( Mw 7.7) earthquake being the most recent example of the region's seismogenic potential (Figure 1). Among past events, the 1819 earthquake ( M > 7.5) is well known and is quoted in the early geologic literature for the dramatic coseismic topographic changes associated with it, including the formation of the elevated tract of land called the Allah Bund (Lyell, 1857). Occurrence of two large earthquakes during a short span of 180 years gives an exceptional status to this seismic zone, considered to be part of the stable peninsular shield of India (Johnston, 1989). In addition to these, several moderate events are reported to have occurred in this region. These earthquakes are suggestive of the existence of multiple seismogenic faults in this region, but very little is known about their past histories, adding more uncertainty to the regional hazard assessment. Our search in the epicentral area of the 1819 earthquake led to the identification of another event between 800 and 1,000 years B.P. (Rajendran and Rajendran, 2001a). Based on the relative size and frequency of older sandblows, we interpreted that the earlier earthquake may have also originated from the same source. However, we recognize that isolating earthquake sources using paleoliquefaction features is not an easy task, particularly where large areas of high liquefaction susceptibility are affected by each event. The problem is more complex in regions where multiple sources exist. For example, until the occurrence of the 2001 earthquake, the Allah Bund region was the only known source of large earthquakes in the Kachchh region (Figure 2). Rajendran et al. , (2001) reported large sandblow craters formed by the Bhuj earthquake close to the 1819 source. If distant …