Seismic Attenuation in the Vicinity of the Geothermal Anomaly at Urach Obtained from Near-Vertical Reflection PROFILES1
Seismic Attenuation in the Vicinity of the Geothermal Anomaly at Urach Obtained from Near-Vertical Reflection PROFILES1
复制标题
从近垂直反射剖面获得的乌拉赫地热异常附近的地震衰减
DOI：
10.1111/j.1365-2478.1988.tb02157.x
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
H. Trappe
中科院分区：
文献类型：
--
作者：
H. Trappe
通过两个近垂直反射剖面确定了乌拉赫地热异常附近的衰减。沉积物和地壳上层（3-4公里深）的衰减是通过对第一波（折射）到达的解释来估计的。为了计算衰减，使用相对于距离的振幅衰减。根据旅行时曲线推导出了扩展因子的校正，即几何振幅发散。在异常之下，观测到的衰减值（Q−1 <$0.008）高于未扰动地壳（Q−1 <$0.002）。这种效应可能是由于结晶基底上部的裂缝和裂隙。
中地壳和下地壳的衰减是利用该深度段的近垂直反射确定的。使用频谱比方法导致热流异常下方的有效衰减Q− 1 eff值高于“正常”地壳。这个高Q− 1 eff区与热流异常下方的低速体相一致。这两种效应，即较高的衰减和较低的速度，可能是由地壳中的高温、裂缝和裂缝造成的。
The attenuation in the vicinity of the geothermal anomaly at Urach was determined by means of two near-vertical reflection profiles. The attenuation in the sediments and in the upper crust (3-4 km depth) was estimated by interpretation of the first (refracted) arrivals. For calculating the attenuation, the amplitude decay with respect to distance was used. Corrections for the spread factor, i.e. the geometric amplitude divergence was deduced from the traveltime curves. Below the anomaly, higher attenuation values (Q−1∼ 0.008) were observed compared with those in the undisturbed crust (Q−1∼ 0.002). This effect is probably due to the cracks and fissures in the upper part of the crystalline basement.
The attenuation in the middle and lower crust was determined using near-vertical reflections from this depth interval. The use of the spectral ratio method leads to higher values of the effective attenuation Q−1eff below the heat flow anomaly compared to those of the‘ normal’crust. This zone of high Q−1eff coincides with the low velocity body below the heat flow anomaly. Both effects, the higher attenuation and the lower velocities, could be caused by high temperatures, cracks and fissures in the crust.