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Swiss Re insures primary insurance companies throughout the world against earthquake losses that exceed the capacity of the primary carriers. The USGS, a federal science agency that assesses the impact of natural hazards and resources on society, has developed new tools to gauge the likelihood of future earthquakes. This Cooperative R&D Agreement launches an international collaboration to develop a comprehensive description and understanding of earthquake occurrence in greater Tokyo. The tendency of earthquakes to interact will be explicitly built into the model through elastic and viscous stress transfer, the first time this has been attempted in such a complex faulting environment. Our objective is a model capable of explaining the salient features of the historical earthquake occurrence and deformation. The model will therefore be rigorously tested against the 400-year-long record of large earthquakes in and around Tokyo; the distribution and rate of contemporary microseismicity; and GPS displacements at the earth’s surface. We will then use the model to develop time-dependent probabilistic forecasts for earthquake occurrence during the next years to decades. This work will be fully vetted by scientists in Japan, the U.S., and by our collaborators at Swiss Re. The results will be published expeditiously in the scientific literature and will be accessible on the web in English and Japanese. The Agreement permits the USGS and the AFRC to focus on a site of outstanding scientific and societal importance, accelerate the pace of research, and see its work put in use by a key practitioner. Swiss Re is afforded a potentially more accurate assessment of earthquake hazard, essential to its business and that of its clients.

Relentless population growth of Japan’s capital during the past century has intruded upon Tokyo Bay. The blue area was reclaimed before 1900, purple in 1900-1955, orange in 1956-1975, yellow after 1976. From National Geographic Magazine (2002).

TOKYO and its outlying cities are home to almost one-quarter of Japan’s 127 million people. Tokyo dominates Japan’s politics, arts, finance, trade, and communications, and accounts for a third of its wealth. Eighty years ago, the region suffered one of the world’s most destructive earthquakes, killing 143,000 people, destroying two-thirds of Tokyo, and all of Yokohama. The earthquake left $68 billion in property damage, ten times that wrought by the 1995 M=6.9 Kobe earthquake. Today, the population of greater Tokyo is six times larger than it was in 1923. To accommodate this growth, about 385 square kilometers of land rimming Tokyo Bay, or about a quarter of the bay, has been reclaimed for urban and industrial use. A repeat of the 1923 M=7.9 Kanto earthquake is estimated to cause 30-60,000 deaths 80-100,000 hospitalized injuries, and total economic losses of $2.1-3.3 trillion, comprised equally of property and business-interruption losses. Insured losses were estimated to be $31-36 billion.

But how likely is a repeat of the Kanto earthquake, or are other types and locations of destructive earthquakes more probable today? Answering this question is the goal of our proposed Cooperative Research & Development project, a focused international collaboration between the Cat Perils and Retro Section, Chief Underwriting Office, Property & Casualty of Swiss Reinsurance Company (Swiss Re) in Zurich, and scientists at the U.S. Geological Survey, the Geological Survey of Japan, Japan’s National Research Institute for Earth Science and Disaster Prevention, and the Geographical Survey Institute of Japan.

Swiss Re announced its sponsorship of a new scientific study, to be conducted by a joint team of US and Japanese scientists. The study aims for an improved understanding of the probability of earthquake occurrence in the Greater Tokyo area.