Damage Patterns

This chapter provides an overview of the macroseismic effects of the Bhuj earthquake. Such information is useful for several reasons. First, direct information about the vulnerability of structures to strong ground motion is useful for assessing, and perhaps mitigating, the hazard posed to similar structures by future large earthquakes. Secondly, given the paucity of instrumental recordings of the Bhuj earthquake, macroseismic data can provide useful information about the spatial variation of ground motions. Finally, detailed damage assessments for this earthquake can be compared to available accounts of historic earthquakes in India and other similar tectonic regimes around the world. These comparisons will provide additional insight into the magnitude of important earthquakes for which there are few or no instrumental recordings. The Bhuj earthquake is of particular interest because of the possibility that it represents an analog for the principal New Madrid (central United States) earthquakes of 1811-1812. The Bhuj earthquake occurred much closer to an active plate boundary than did the New Madrid events, and the Bhuj earthquake might therefore be considered a plate boundary-related event. However, in both cases, the regions primarily affected by the earthquake are stable continental interiors with low attenuation. A quantification of damage patterns, such as that presented in this chapter, can provide useful insight into the attenuation and frequency content of ground motions, which may in turn be useful in resolving whether the Bhuj earthquake should be considered interplate or intraplate for the purpose of data classification. This chapter combines two different approaches to quantify macroseismic effects of the Bhuj earthquake. First, a large-scale map of intensities was compiled based on media accounts. Second, ground-level surveys of damage in towns and villages across the epicentral area by the India-U.S. Geotechnical Earthquake Engineering Reconnaissance Team were synthesized. This approach provides both coarse- and fine-scale overviews of damage, as well as an opportunity to compare detailed ground-based intensity results to a "broad brush" intensity value determined from one or a small handful of media accounts for any one location