Imaging the magmatic system of Newberry Volcano using joint active source and teleseismic tomography
Imaging the magmatic system of Newberry Volcano using joint active source and teleseismic tomography
复制标题
使用联合主动源和远震层析成像对纽伯里火山的岩浆系统进行成像
DOI：
10.1002/2015gc006129
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发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
M. Bezada
中科院分区：
文献类型：
--
作者：
B. Heath;E. Hooft;D. Toomey;M. Bezada
本文利用联合收割机主动和被动P波地震资料对喀斯喀特弧以东的纽贝里火山下的岩浆系统进行层析成像。利用近距离地震仪（300-800 m）记录的局部活动震源的走时和近震的延迟时间，我们显著地提高了上地壳（<10 km深度）速度结构的恢复。层析成像模型揭示了位于破火山口下方3至5公里深度之间的低速特征，与岩浆体一致。与早期的层析成像研究相反，在早期的层析成像研究中，升高的温度足以解释恢复的低速度，我们的联合层析成像模型中的较大幅度的低速度异常需要低程度的部分熔化（10%），最小熔化体积为2.5立方千米。此外，合成测试表明，需要更大幅度的低速异常，以及推断更大体积的岩浆（高达8立方公里）来解释观测到的波形变化。推测的岩浆体的横向范围和形状表明，纽贝里的伸展构造体制影响了岩浆侵入体的定位。我们的研究表明，联合反演主动源和被动源地震数据，提高了火山系统的地壳浅层地震结构的层析成像，主动源实验将受益于更长的部署时间，也记录火山源。
In this paper, we combine active and passive source P wave seismic data to tomographically image the magmatic system beneath Newberry Volcano, located east of the Cascade arc. By using both travel times from local active sources and delay times from teleseismic earthquakes recorded on closely spaced seismometers (300–800 m), we significantly improve recovery of upper crustal velocity structure (<10 km depth). The tomographic model reveals a low‐velocity feature between 3 and 5 km depth that lies beneath the caldera, consistent with a magma body. In contrast to earlier tomographic studies, where elevated temperatures were sufficient to explain the recovered low velocities, the larger amplitude low‐velocity anomalies in our joint tomography model require low degrees of partial melt (∼10%), and a minimum melt volume of ∼2.5 km3. Furthermore, synthetic tests suggest that even greater magnitude low‐velocity anomalies, and by inference larger volumes of magma (up to 8 km3), are needed to explain the observed waveform variability. The lateral extent and shape of the inferred magma body indicates that the extensional tectonic regime at Newberry influences the emplacement of magmatic intrusions. Our study shows that jointly inverting active source and passive source seismic data improves tomographic imaging of the shallow crustal seismic structure of volcanic systems and that active source experiments would benefit from longer deployment times to also record teleseismic sources.