shallow magma plumbing system at Rabaul caldera, Papua new Guinea

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In order to investigate the magma system of this Rabaul caldera and to evaluate the recent activities of the volcanoes, an international scientific research project was performed from 2001 to 2003. During 2001-2003, Japanese team visited Rabaul three times and made cooperative observations with the Rabaul volcanological Observatory (RVO). In 2001, we clarified basic chronology for tephras from 1994 and some historical eruptions and collect rock samples for further chemical analyses. Geochemical surveys were carried out in 2002 and 2003. Fumarolic gases and hot spring water were samples on the foot of Tavurvur Volcano. C02 flux from ground surface were measured repeatedly around Simpson harbor in order to evaluate spacial distribution of the anomaly and monitor the magma activity. During our survey in 2002 and 2003, Tavurvur emitted ash with Vulcanian eruptions and small explosions that occurred frequently. Chemical analysis of water leachates of the ash was useful for remote monitoring of the volcano. Tsunami deposits caused by the 1994 eruptions were identified as sand layers or characteristic pumiceous sand layers sandwiched by tephras from both Vulcan and Tavurvur Volcanoes. The chronological studies of both tephra and tsunami deposits was done to reveal the tsunamigenic volcanic process in the 1994 eruption series.