Broadband Seismic Studies of Dome Growth at Merapi Volcano, Indonesia

EAR-0001199 Voight，巴里1998年，在默拉皮火山（印度尼西亚爪哇）山顶部署了为期一个月的宽带地震仪，获得了与活动安山质圆顶生长相关的火山地震的显着数据集。 这些地震，传统上称为多相（MP）事件，通常以短周期台站上的3 - 4 Hz地面运动为特征。 然而，在穹顶几百米范围内收集的数据显示，叠加在MP波形上的相对高振幅、独特的、非常长周期（4秒）的水平地面运动，在许多事件中，同一台站的波形几乎相同。 在距离较远的宽带站上，观察不到甚长周期的脉冲。 水平地面运动的优势，脉冲幅度随距离衰减，站附近的熔岩穹丘，和现代宽带地震仪的字符的密切接近都表明，这些变形脉冲是由于动态的，近场倾斜所造成的熔岩挤出过程中积极增长的默拉皮圆顶。 提出了一个为期两年的项目，利用数值方法分析这些数据，计算合成位移和旋转场，并进行为期一个月的PASSCAL/RAMP部署宽带地震仪，结合高数据率倾斜测量，以收集更多的数据，在预期的持续活动在默拉皮。 这项研究的结果将有重要的影响，在解释与火山过程相关的宽带信号，并可能导致从根本上新的认识与活跃的火山穹隆增长的地震过程。

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.