Interactive comment on "High-resolution shear wave reflection seismics as tool to image near-surface subrosion structures - a case study in Bad Frankenhausen, Germany" Wadas et. al., 2016

2016 ◽  
Author(s):  
Janina Kammann
Keyword(s):  
High Resolution ◽  
Shear Wave ◽  
Wave Reflection ◽  
Near Surface ◽  
Reflection Seismics

scholarly journals High-resolution shear wave reflection seismics as tool to image near-surface subrosion structures – a case study in Bad Frankenhausen, Germany

2016 ◽  
Author(s):  
Sonja Wadas ◽  
Ulrich Polom ◽  
Charlotte Krawczyk
Keyword(s):  
High Resolution ◽  
Shear Wave ◽  
Wave Reflection ◽  
Horizontal Shear ◽  
Seismic Profiles ◽  
Near Surface ◽  
Reflection Seismics ◽  
Seismic Sections ◽  
The Church

Abstract. 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 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 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 environment with a horizontal resolution of less than 1m in the uppermost 10–15 m.

On the prediction of settlement from high-resolution shear-wave reflection seismic data: The Trondheim harbour case study, mid Norway

2013 ◽  
Vol 167 ◽  
pp. 72-83 ◽  
Author(s):  
J.S. L'Heureux ◽  
M. Long ◽  
M. Vanneste ◽  
G. Sauvin ◽  
L. Hansen ◽  
...  
Keyword(s):  
High Resolution ◽  
Shear Wave ◽  
Seismic Data ◽  
Wave Reflection ◽  
Reflection Seismic

Shear-wave reflection seismics as a valuable tool for near-surface urban applications

2013 ◽  
Vol 32 (3) ◽  
pp. 256-263 ◽  
Author(s):  
Charlotte M. Krawczyk ◽  
Ulrich Polom ◽  
Thies Beilecke
Keyword(s):  
Shear Wave ◽  
Wave Reflection ◽  
Near Surface ◽  
Reflection Seismics

scholarly journals High-resolution shear-wave seismic reflection as a tool to image near-surface subrosion structures – a case study in Bad Frankenhausen, Germany

Solid Earth ◽  
2016 ◽  
Vol 7 (5) ◽  
pp. 1491-1508 ◽  
Author(s):  
Sonja H. Wadas ◽  
Ulrich Polom ◽  
Charlotte M. Krawczyk
Keyword(s):  
High Resolution ◽  
Shear Wave ◽  
Urban Areas ◽  
Seismic Reflection ◽  
Seismic Velocities ◽  
Horizontal Shear ◽  
Near Surface ◽  
Seismic Sections ◽  
The Church

Abstract. 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 seismic reflection 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 to be a main pathway for water to leach the evaporite. The seismic profiles were acquired with the horizontal micro-vibrator ELVIS, developed at Leibniz Institute for Applied Geophysics (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 heavily fractured, (3) formation of depression structures in the near-surface, (4) diffractions in the unmigrated seismic sections that indicate increased scattering of the seismic waves, and (5) varying seismic velocities and low-velocity zones that are presumably caused by fractures and upward-migrating cavities. A previously undiscovered southward-dipping listric normal fault was also found, to the north of the church. It probably serves as a pathway for water to leach the Permian formations below the church and causes the tilting of the church tower. This case study shows the potential of horizontal shear-wave seismic reflection to image near-surface subrosion structures in an urban environment with a horizontal resolution of less than 1 m in the uppermost 10–15 m.

scholarly journals Shallow shear-wave reflection seismics in the tsunami struck Krueng Aceh River Basin, Sumatra

2008 ◽  
Vol 14 ◽  
pp. 135-140 ◽  
Author(s):  
U. Polom ◽  
I. Arsyad ◽  
H.-J. Kümpel
Keyword(s):  
High Resolution ◽  
Shear Wave ◽  
Site Effects ◽  
Wave Reflection ◽  
P Wave ◽  
Site Classification ◽  
Seismic Site Effects ◽  
Reflection Seismics ◽  
The City ◽  
Banda Aceh

Abstract. As part of the project "Management of Georisk" (MANGEONAD) of the Federal Institute for Geosciences and Natural Resources (BGR), Hanover, high resolution shallow shear-wave reflection seismics was applied in the Indonesian province Nanggroe Aceh Darussalam, North Sumatra in cooperation with the Government of Indonesia, local counterparts, and the Leibniz Institute for Applied Geosciences, Hanover. The investigations were expected to support classification of earthquake site effects for the reconstruction of buildings and infrastructure as well as for groundwater exploration. The study focussed on the city of Banda Aceh and the surroundings of Aceh Besar. The shear-wave seismic surveys were done parallel to standard geoengineering investigations like cone penetrometer tests to support subsequent site specific statistical calibration. They were also partly supplemented by shallow p-wave seismics for the identification of (a) elastic subsurface parameters and (b) zones with abundance of groundwater. Evaluation of seismic site effects based on shallow reflection seismics has in fact been found to be a highly useful method in Aceh province. In particular, use of a vibratory seismic source was essential for successful application of shear-wave seismics in the city of Banda Aceh and in areas with compacted ground like on farm tracks in the surroundings, presenting mostly agricultural land use areas. We thus were able to explore the mechanical stiffness of the subsurface down to 100 m depth, occasionally even deeper, with remarkably high resolution. The results were transferred into geotechnical site classification in terms of the International Building Code (IBC, 2003). The seismic images give also insights into the history of the basin sedimentation processes of the Krueng Aceh River delta, which is relevant for the exploration of new areas for construction of safe foundations of buildings and for identification of fresh water aquifers in the tsunami flooded region.

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