High-resolution shear wave reflection seismics as tool to image near-surface subrosion structures n a case study in Bad Frankenhausen, Germany
High-resolution shear wave reflection seismics as tool to image near-surface subrosion structures n a case study in Bad Frankenhausen, Germany
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德国巴特弗兰肯豪森案例研究中高分辨率剪切波反射地震作为近地表腐蚀结构成像工具
DOI：
10.5194/se-2016-91
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
C. Krawczyk
中科院分区：
文献类型：
--
作者：
S. Wadas;U. Polom;C. Krawczyk
浸蚀是可溶性岩石的地下浸出，导致凹陷和塌陷结构的形成。这种全球现象是城市地区的地质灾害。为了研究近地表腐蚀结构，共绘制了 4 条剪切波反射地震剖面，总长度约为 4 条。围绕德国图林根州北部著名的巴特弗兰肯豪森倾斜教堂塔楼进行了 332 m 的测试，该塔楼与垂直方向的倾斜度为 4.93°。图林根州大部分地下地质特征是可溶性二叠纪沉积物，Kyffhäuser-Southern-Margin 断层被认为 5 是水浸出蒸发岩的主要通道。地震剖面是通过 LIAG 开发的水平微振动器 ELVIS 和配备 72 个水平地震检波器的 72 m 长陆地拖缆采集的。高分辨率地震剖面显示了深度约 100 米的潜蚀诱发结构。 100 m，揭示了与二叠纪沉积物淋滤相关的五个特征：（1）由强烈异质地层引起的横向和垂直变化的反射模式，（2）不连续的反射体、小偏移和断层，这表明地下强烈断裂，（3）近地表中形成凹陷结构，（4）未迁移的地震剖面中的衍射表明地震波的散射增加，（5）变化的地震速度和低速区这可能是由裂缝和向上迁移的空洞引起的。还发现了一个先前未被发现的向南倾斜的列表正断层，位于教堂的北面。它可能是水渗滤教堂下方 Zechstein 地层的通道，导致塔楼倾斜。该案例研究展示了水平剪切波反射地震在城市环境中近地表侵蚀结构成像中的潜力，在最上部 10-15 m 的水平分辨率小于 1 m。
Subrosion is the subsurface leaching of soluble rocks that results in the formation of depression and collapse structures. This global phenomenon is a geohazard in urban areas. To study near-surface subrosion structures four shear-wave reflection seismic profiles with a total length of ca. 332 m were carried out around the famous leaning church tower of Bad Frankenhausen in northern Thuringia, Germany, which shows an inclination of 4.93° from the vertical. Most of the geological underground of Thuringia is characterized by soluble Permian deposits, and the Kyffhäuser-Southern-Margin Fault is assumed 5 to be a main pathway for water to leach the evaporite. The seismic profiles were acquired with the horizontal micro-vibrator ELVIS developed at LIAG and a 72 m long landstreamer equipped with 72 horizontal geophones. The high-resolution seismic sections show subrosion-induced structures to a depth of ca. 100 m and reveal five features associated with the leaching of Permian deposits: (1) lateral and vertical varying reflection patterns caused by strongly heterogeneous strata, (2) discontinuous reflectors, small offsets and faults, which show the underground is strongly fractured, (3) formation of depression structures in 10 the near-surface, (4) diffractions in the unmigrated seismic sections that indicate an increased scattering of the seismic waves, (5) varying seismic velocities and low-velocity zones that were presumably caused by fractures and upward-migrating cavities. A previously undiscovered southward-dipping, listric normal fault was also found, located northward of the church. It probably serves as a pathway for water to leach the Zechstein formations below the church and causes the tilting of the tower. This case study shows the potential of horizontal shear-wave reflection seismics in imaging near-surface subrosion structures in an urban 15 environment with a horizontal resolution of less than 1 m in the uppermost 10–15 m.