Advances for Tsunami Measurement Technologies and Its Applications

Abstract

After the Indian Ocean tsunami from the Sumatra earthquake on 26 December 2004 (Mw > 9.0), we have realized the importance of the early tsunami warning system and its necessity for mitigating the tsunami disaster. This catastrophic event was a cue for construction of the Indian Ocean early tsunami warning system, and first of all, a global tsunami forecast system was established together with the Pacific Ocean tsunami warning system operated by U.S. and Japan. The Indian Ocean tsunami motivated the international scieity to construct global tsunami warning systems, which include seismic and sea level monitoring measurements. National Centre of Geosciences in Germany, for example, would challenge to detect relative initial tsunami height distribution by GPS arrays and the seismic stations on land, and deploy GPS buoys along the Sumatra trench for establishment of an early tsunami warning system in Indonesia. And finally the German-Indonesian Tsunami Early Warning System (GITEWS) become into operation in 2010 (e.g., Rudloff et al., 2009; Munch et al., 2011). Before the Indian Ocean tsunami in 2004, only tide gauge records are available data in the most countries surrounding the Indian Ocean (e.g., Merrifield et al., 2005; Matsumoto et al., 2009). Moreover, some of them were not transfered in real-time but were recorded and avaliable only inside the tide gauge stations. Instrumentally observed tsunami data acquired in real-time is qualitatively used for tsunami warning issue followed by its modification and cancellation. If characteristics of forthcoming tsunami would be understood in advance, it must be helpful and useful for tsunami related disaster mitigation. Tsunami height and arrival time are the most important information after the tsunamigenic earthquake occurrence, and they are often used as tsunami observation information. Tsunami observation is traditionally carried out by tide gauges at the coast. Recently, technological development has been promoted to estimate tsunami features as early as possible. This chapter reviews tsunami measurement technologies and instruments, in particularly developed in Japan and introduces an actual tsunami observation in the source area, which became possible after the offshore tsunami observation in the last decade. In the end, potential use for early tsunami detection is discussed by applying to the presumed megathrust earthquake in the Nankai trough, SW Japan.