Science of Tsunami Hazards (Jan 2011)
THE TSUNAMIS OF JANUARY 3, 2009 IN INDONESIA AND OF JANUARY 15, 2009 IN SIMUSHIR AS RECORDED IN THE SOUTH KURIL ISLANDS
Abstract
Bottom pressure gauges installed by the Institute of Marine Geology & Geophysics RAS in Shikotan Island, Kitoviy Bay (Iturup Is.) and near Cape Van der Linde (Urup Is.), recorded two tsunamis during the month of January 2009. The first of the recorded tsunamis was generated by the January 3, 2009 earthquake in Indonesia and the second by the January 15, 2009 Simushir Island earthquake in the nearby seismic zone of the South Kuril Islands. The two tsunamis were additionally recorded by tide gauges at Hanasaki (Hokkaido Is.) and Malokurilskaya Bay (Shikotan Is.), but with considerable delay of the Indonesian tsunami from its estimated time of arrival. The tsunami travel time delay can be attributed to effects of energy trapping by Japan’s continental shelf. The maximum height of the Simushir tsunami (97 cm in the Kitoviy Bay) was also observed much later than the arrival of the first wave. Totally, the oscillations lasted for about 32 hours, which is very long time period for the relatively weak tsunami. The present study investigates these apparent anomalies of the long wave oscillations and whether they were caused by reflected waves from the original earthquake or from a secondary tsunami generated by a weaker aftershock.
