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1982和1983年夏季期间,在Long谷-Mono火山口地区完成了十条新的地震折射剖面的野外观测工作,该地区位于Sierra Nevada东部和盆地山脉省之间的构造活动带内．本文所提供的四条剖面,给出了下列地区地壳上部7-10km内结构的实例：Long谷破火山口西半部、Mono火山口环状断裂系统、以及Long谷以北和东北的“正常”地壳．这整个区域有一个主要由中生代花岗岩组成的、共同的结晶基底.在地表以下2km深处,P波速度均匀,约为5．6km/s；而在此深度以下,速度大约以0．1 km/s的梯度增加．根据穿越破火山口西部的一条剖面观测到的、清晰的续至波证实了1972年折射剖面的结果：即在附生圆丘(resurgentdome)西缘下方7-8km处有一个反射界面,这可能是一个岩浆房的顶部．对地壳上部2km内细结构的解释得到下列结论： (1)在深度小于2km的结晶基底中,P波速度从3．6变化到5．0 km/s．这种变化反映了基底上部断裂发育程度的差异(2)在Mono火山口环状断裂下方、上部7-10km以内的基底显然是均匀的,这表明：如果那里有大的岩浆房,其深度至少应有10km．(3)在Long谷破火山口西半部地区下方,下降的结晶基底稍微(5-10°)朝东北方向倾斜．这个破火山口的北边、西边和南边,沿着陡倾的破火山口边界断层,视断距为1．0-1．7km,而其北边的断距最大．(4)构成这个破火山口填充物的岩石基本上有三组P波速度：①从地表向下100-400m的速度值为1．2-1．8km/s,其物质组分相当于未固结的河相或湖相沉积、或为非常破碎的流纹岩；②再向下200-400m,速度为2．8-3．1 km/s,相应的物质是有稀疏节理的次火山口流纹岩、流纹英安岩和玄武岩流；③再向下大约1000m,速度为3．9-4．4km/s,其物质为Bishop凝灰岩沉积．
Ten field observations of the seismic refraction profile were completed in the Long Valley-Monte Volcano in the summer of 1982 and 1983, and are located in the tectonic belt between eastern Sierra Nevada and the Basin Sierra Leone. The four sections presented here provide examples of structures within 7-10 km of the upper crust of the following areas: the western half of the Long Valley caldera, the Mono crater ring fracture system, and the “normal” north and northeast of the Long Valley Crust. The whole area has a common crystalline base consisting mainly of Mesozoic granites, with a uniform P wave velocity of about 5.6 km / s below a depth of 2 km below the surface, and below this depth a velocity of about 0.1 km / s gradient increases. The clear continuation of the wave observed on a section through the western part of the caldera confirms the result of the 1972 refrac- tional profile: a reflection interface 7-8 km below the western edge of the resurgent dome It is the top of a magma chamber. The interpretation of the fine structure within 2km above the crust results in the following conclusions: (1) The P-wave velocity changes from 3.6 to 5.0 km / s in crystalline substrates less than 2 km in depth. This change reflects the difference in the extent of fracture development in the upper part of the basement. (2) Below the ring-shaped rupture of the Mono crater, the base within 7-10 km of the upper part is apparently uniform, indicating that if there is a large magma chamber, its depth is at least Should have 10km. (3) Below the western half of the Long Valley caldera, the descending crystalline basement slopes northeast slightly (5-10 °). The north, west and south of this caldera, along the steep, caldera boundary fault, are at a distance of 1.0-1.7km, with the largest offsets to the north. (4) There are basically three sets of P-wave velocities in the rocks that make up this caldera fill: (1) the velocity of 100-400 m down from the surface is 1.2-1.8 km / s, Knot river facies or lacustrine deposits, or very broken rhyolite; ② and then down 200-400m, the velocity of 2.8-3.1 km / s, the corresponding material is a sparsely-subducted sub-crater flow Rhyolite, rhyolite dacite, and basalt flow; and then down about 1000m, the velocity of 3.9-4.4km / s, its material is Bishop tuff deposition.