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在本文中,我们用近震台网记录得很好的天然地震资料,研究黄石国家公园地区的V_p/V_s和泊松比(σ)的变化。我们发现,在具有地热活动性的黄石破火山口内地区的V_p/V_s平均值比破火山口外地区的大约低7％。而在破火山口本身、具有水热活动的一些区域,V_p/V+s值可能又降低2-7％,这些区域包括:Norris间歇喷泉盆地(Norris Geyser Basin),上、下间歇喷泉盆地(Upper and Lower Geyser Basins),黄石湖和泥火山(Mud Volcano)。在考虑了可能引起Vp/Vs变化的各种原因(如:地质和构造的差异、热效应、部分熔融和水热活动性)之后,我们得出结论:观测到的Vp/Vs减小的似乎最合理的解释,是在破火山口地热储集层中、存在着温度和孔隙压力接近水—蒸汽相变条件下的热水。
In this paper, we study the changes of V_p / V_s and Poisson’s ratio (σ) in the Yellowstone National Park by using well-recorded natural seismic data from near-nematic seismic stations. We find that the V_p / V_s average in the geothermally active Yellowstone Caldera is about 7% lower than in the area outside the Caldera. In some areas with hydrothermal activity on the Caldera itself, V_p / V + s may be reduced by another 2-7%. These areas include the Norris Geyser Basin, the Upper and Lower Geyser Basin Upper and Lower Geyser Basins, Yellowstone Lake and Mud Volcano. After considering various reasons that may cause changes in Vp / Vs (eg, differences in geology and tectonics, thermal effects, partial melting, and hydrothermal activity), we conclude that the observed decrease in Vp / Vs seems most A reasonable explanation is that in the geothermal reservoirs of the Caldera, there is hot water with temperature and pore pressure near the water-vapor phase transition.