Broadband Seismic Studies of Dome Growth at Merapi Volcano, Indonesia

1998年在印度尼西亚爪哇的默拉皮火山顶端部署了长达一个月的宽带地震仪，产生了与活跃的安山期穹顶生长有关的火山地震的显著数据集。这些地震，传统上被称为多相(MP)事件，通常以短周期台站上3-4赫兹的地面运动为特征。然而，在圆顶几百米范围内收集的数据显示，相对较高的振幅、独特的、极长周期(4秒)的水平地面运动叠加在MP波形上，在许多事件中，同一观测站的波形几乎相同。在距离较远的宽带站上观察不到超长周期脉冲。水平地面运动的优势、脉冲幅度随距离的衰减、熔岩穹顶附近台站的接近以及现代宽带地震仪的特征都表明，这些形变脉冲是由于活跃增长的默拉皮穹顶熔岩挤压过程造成的动态近场倾斜所致。提出了一个为期两年的项目，用数值方法分析这些数据，计算合成位移和旋转场，两个项目进行为期一个月的宽带地震仪PASSCAL/RAMP部署，结合高数据率倾斜测量，以在Merapi预期的持续活动期间收集更多数据。这项研究的结果将对解释与火山过程有关的宽带信号具有重要意义，并可能从根本上导致对与活跃的火山穹隆生长有关的地震过程的新理解。

EAR-0001199Voight, Barry A month-long deployment of broadband seismographs at the summit of Merapi volcano (Java, Indonesia) in 1998 has yield a remarkable data set of volcanic earthquakes associated with active andesitic dome growth. These earthquakes, traditionally termed multiphase (MP) events, are usually characterized by 3-4 Hz ground motions on short-period stations. However, data collected within a few hundred meters of the dome showed relatively high-amplitude, distinctive, very-long-period (4 sec) horizontal ground motions superposed on the MP waveforms, with nearly identical waveforms at the same stations over many events. Very-long-period pulses are not observed at broadband stations at greater distance. Dominance of horizontal ground motions, pulse amplitude decay with distance, the close proximity of stations near lava dome, and character of modern broadband seismographs all suggest that these deformational pulses are due to dynamic, near-field tilts caused by lava extrusion processes at the actively growing Merapi dome. A two year-project is proposed to analyze these data using numerical methods to compute synthetic displacement and rotation fields and two conduct a one-month long PASSCAL/RAMP deployment of broadband seismographs, in conjunction with high-data-rate tiltmetry, to collect more data during expected sustained actiity at Merapi. The results of this study will have important implications in interpreting broadband signals associated with volcanic processes, and may lead to fundamentally new understanding of seismic processes associated with active volcanic dome growth.