shallow magma plumbing system at Rabaul caldera, Papua new Guinea

为了调查拉包尔火山口的岩浆系统并评估火山的近期活动，2001年至2003年进行了一项国际科学研究项目。2001-2003年期间，日本小组三次访问拉包尔，并与拉包尔火山观测站进行了合作观测。2001年，我们澄清了1994年以来火山岩和一些历史喷发的基本年代学，并收集了岩石样品进行进一步的化学分析。2002年和2003年进行了地球化学调查。在塔武尔火山脚下采集了富马酸气体和温泉水样本。在辛普森港附近对地表CO2通量进行了多次测量，以评价异常的空间分布，监测岩浆活动。在我们2002年和2003年的调查期间，塔武尔火山喷发出火山灰，经常发生小爆炸。对火山灰的水浸出物进行化学分析有助于对火山进行远程监测。由1994年火山爆发引起的海啸沉积物被确定为砂层或特征浮岩砂层夹在火山灰和Tavurvur火山。通过火山碎屑和海啸沉积物的年代学研究，揭示了1994年火山喷发系列中的海啸成因火山作用。

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.