Seismic Properties of Rocks from an Active Volcanic System: Long Valley Caldera, California

[参考译文]高分辨率地震技术的进步表明，有可能对活跃或休眠的爆炸性火山系统的管道系统进行成像。为了解释从这些研究中获得的纵波和横波速度数据，重要的是要彻底了解控制地震速度的变量（岩浆、热液蚀变、裂缝、岩石孔隙度、水和/或蒸汽饱和度、水和/或蒸汽孔隙压力升高以及岩石成分的变化）。为此，该研究项目将调查构成加州长谷火山口的岩石的物理性质。密集的地球物理实验、地质研究和热液系统的钻探提供了一个无与伦比的大型火山口系统内部的视图。包括长谷探井在内的许多火山口内钻孔的样本，提供了一个机会来检查火山口上方三公里内岩石的地震速度变化。这些钻孔穿透了这个巨大火山系统的主要裂口内成分：各种破火山口后流纹岩和玄武岩、毕晓普凝灰岩和西兰基底岩。实验室测量将对从火山口内钻孔和流出沉积物中回收的岩心进行，包括P波和S波速度作为围压、孔隙流体压力和温度的函数。对矿物学和化学成分、孔隙几何形状、孔隙体积、密度、性质和蚀变程度以及其他结构参数的配套分析将有助于量化地震速度的控制。这项研究将是第一次系统地研究在高围压、高温和孔隙压力下测量的大型爆炸性硅火山口系统成分的地震特性。

EAR-9980548: David M Fountain and Barbara E John Advances in high-resolution seismic techniques indicate that it may be possible to image plumbing systems of active or dormant explosive volcanic systems. In order to interpret P- and S- wave velocity data obtained from these studies, it is important to thoroughly understand the variables that control seismic velocities (magma, hydrothermal alteration, fractures, rock porosity, water and/or steam saturation, elevated pore pressure of water and/or steam, and variations rock composition). Toward this end, this research project will investigate the physical properties of rocks comprising the large Long Valley Caldera, California. Intensive geophysical experiments, geological studies, and drilling in the hydrothermal system provide an unparalleled view of the interior of a large caldera system. Samples from the numerous intracaldera drill-holes, including the Long Valley Exploratory Well, afford an opportunity to examine variations in seismic velocities of rocks within the upper three kilometers of the caldera. These drill-holes penetrate the main intracaldera components of this giant volcanic system: various post-caldera rhyolites and basalts, the Bishop Tuff, and Sierran basement rocks. Laboratory measurements will be conducted on core recovered from intracaldera drill-holes and outflow deposits and include P- and S- wave velocities as a function of confining pressure, pore fluid pressure, and temperature. Companion analysis of mineralogical and chemical composition, pore geometry, pore volume, density, nature and degree of alteration, and other textural parameters will allow quantification of the controls on seismic velocity. This study will be the first systematic study of the seismic properties of the constituents of large explosive silicic caldera systems measured at elevated confining pressure, high temperature, and pore pressure.