A new record and geography of tsunamis, earthquakes and tropical cyclones in Bangladesh and their relevance to disaster risk reduction

摘要

Bangladesh is vulnerable to a variety of natural hazards including frequent tropical cyclones and, less commonly, earthquakes and tsunamis. The 1762 event is often cited as evidence for these latter hazard types. Remarkably, little historical data are available to help contribute to disaster risk reduction in Bangladesh. This thesis addresses this gap by documenting and analysing selected histories and geographies of tsunamis, earthquakes and tropical cyclones affecting Bangladesh. This thesis includes a detailed case study of the 1762 earthquake, coupled with deep archival research and field investigations in SE Bangladesh. I construct three new catalogues consisting of 135 tsunamis (between 38000BC and 2009), 562 earthquakes (between 810BC and 2012) and 304 tropical cyclones (between 1000 and 2009) occurring in the Bay of Bengal and Bangladesh. Statistical analysis of tsunami data suggests that the occurrence of a tsunami affecting the coast of Bangladesh and Myanmar is 1% in any given year, and 63% in a century. However, analysis of the 1762 earthquake and associated tsunami suggests that any future event may result in significant damage to homes, loss of numerous lives, and cause significant liquefaction, compaction, landslides, and co-seismic subsidence. The construction of a detailed Modified Mercalli Intensity map using the new earthquake data suggests that this will be useful for supporting risk reduction efforts in Bangladesh. An analysis of the 1970, 1991 and 2007 tropical cyclones suggests that deaths associated with tropical cyclones are declining, but economic damage and other effects are rising. In conducting this research, I discovered that the further back in time one proceeds, the greater the scarcity of data. In developing the catalogues, I identified conflicting data; I analysed discrepancies within the data and reached a predictable conclusion. I conclude that analyses of long-term data help identify new hazard exposure and develop knowledge that can be useful to formulate new disaster risk reduction policies and rectify existing ones in Bangladesh.