Investigating the Possible Role of Magmatically-Derived Fluids in Faulting in the Long Valley Caldera

研究岩浆源流体在长谷破火山口断层作用中的可能作用斯坦福大学地球物理学系这项研究的目的是通过研究加州东部长谷破火山口的地震活动，提高我们对火山和构造过程相互作用的认识。具体地说，我们正在研究岩浆衍生流体在火山口及其附近的断裂力学中的作用。众所周知，高流体压力可通过减小断层间的正应力而引发地震。虽然科学家们怀疑，由于地下水的加热和岩浆中流体的溶解，岩浆室上方的流体压力很高，但岩浆衍生的流体和触发的地震活动之间的明确联系仍然难以捉摸。通过绘制应力场图和量化长谷破火山口与断裂有关的火山影响孔隙压力，我们希望更好地约束深部构造与火山活动之间的关系。流体已被证明能影响各种断裂过程。虽然在诱发地震活动的情况下已经观察到与孔隙流体迁移相关的地震触发，并且已经假设发生在圣安德烈亚斯断层沿线，但还不可能详细量化或绘制相对孔隙压力变化。精确绘制与地震时空传播系统相关的相对孔隙压力图，将有助于我们了解流体压力如何随时间变化，并通过基岩扩散，从而触发这些事件。本项目详细研究了这些过程。

EAR0087494 (PH #37x)INVESTIGATING THE POSSIBLE ROLE OF MAGMATICALLY-DERIVED FLUIDS IN FAULTING IN THE LONG VALLEY CALDERAMark D. ZobackDepartment of GeophysicsStanford UniversityThe goal of this study is to improve our understanding of the interaction of volcanic and tectonic processes by investigating seismic activity in the Long Valley caldera, Eastern California. Specifically, we are studying the role of magmatically derived fluids in the mechanics of faulting in and near the caldera. It is well known that high fluid pressures may trigger earthquakes by decreasing the normal stress across faults. While scientists suspect that fluid pressures are high above magma chambers due to heating of ground water and exsolution of fluids from magma, a clear link between magmatically derived fluids and triggered seismicity remains elusive. By mapping the stress field and quantifying volcanically influenced pore pressures associated with faulting in the Long Valley caldera we hope to better constrain the relationship between tectonic and volcanic activities at depth.Fluids have been shown to influence a variety of faulting processes. Although earthquake triggering associated with pore fluid migration has been observed in cases of induced seismicity and has been hypothesized to occur along the San Andreas Fault, it has not been possible to quantify or map relative pore pressure changes in detail. Precise mapping of relative pore pressures associated with a spatially and temporally propagating system of earthquakes would help us understand how fluid pressures might be changing with time and diffusing through bedrock to trigger these events. This project is studying these processes in detail.