Subsurface Fault and Colluvial Wedge Detection Using Resistivity, Refraction Tomography and Seismic Reflection

With this note, we show a three-dimensional reconstruction of the basal surface of a large-scale and deep-seated rock-slide located in Northern Apennines (Northern Italy), obtained by integrating direct observations from boreholes and data from multi-methods geophysics. This type of landslides is so intrinsically complex and extended, that borehole investigations alone are generally insufficient to fully characterize the inner structures. To overcame such limitations, geophysical surveys are employed extensively (Bogoslovsky and Ogilvy 1977; Bruno and Marillier 2000; Bichler et al. 2004; Jongmans and Garambois 2007). In this study, we integrated multi-parameter data derived from 400 m of DC electrical resistivity tomography (ERT), 466 m of P-wave seismic refraction tomography (SRT), 420 meters of P-wave seismic reflection profile (SRF) together with 156 HVSR seismic noise recordings processed with spectral ratio methodology (Nakamura 1989). To constrain the inversion of the HVSR and migrate to the spatial domain the SRF, the P-wave velocity domains from SRT profiles were used after comparison with stratigraphic data. Moreover, the ERT profile fitted the geometrical features depicted by SRF profile. By means of all these data, we managed to map the surface exhibiting the highest acoustic impedance and the most relevant spatial continuity, which, according to the stratigraphic data, is to be ascribed to the basal interface between the fractured flysch rock masses involved in deep-seated sliding and the underlying undamaged bedrock. Comparison with inclinometer data also showed, presently, the active sliding surfaces match the mapped interface only in some locations, whereas in other they are shallower.&#160; This indicates that the mapped basal surface can be considered the envelope of the maximum volume involved, in the past, by the mass movement, and that part of such volume is nowadays no longer moving. The integration of multi-geophysical surveys, in this case, proved to be a valuable way to spatialize evidences collected by boreholes, providing the basis for a three-dimensional geological model of the slope that can later on be used for modelling purposes.ReferencesBichler, A., P. Bobrowsky, M. Best, M. Douma, J. Hunter, T. Calvert, and R. Burns. 2004. &#8220;Three-Dimensional Mapping of a Landslide Using a Multi-Geophysical Approach: The Quesnel Forks Landslide.&#8221; Landslides 1 (1): 29&#8211;40. https://doi.org/10.1007/s10346-003-0008-7.Bogoslovsky, V A, and A A Ogilvy. 1977. &#8220;GEOPHYSICAL METHODS FOR THE INVESTIGATION OF LANDSLIDES.&#8221; GEOPHYSICS 42 (3): 562&#8211;71. https://doi.org/10.1190/1.1440727.Bruno, F., and F. Marillier. 2000. &#8220;Test of High-Resolution Seismic Reflection and Other Geophysical Techniques on the Boup Lanslide in the Swiss Alps.&#8221; Surveys in Geophysics 21 (4): 333&#8211;48.Jongmans, Denis, and St&#233;phane Garambois. 2007. &#8220;Geophysical Investigation of Landslides: A Review.&#8221; Bulletin de La Societe Geologique de France 178 (2): 101&#8211;12. https://doi.org/10.2113/gssgfbull.178.2.101.Nakamura, Y. 1989. &#8220;Method for Dynamic Characteristics of Subsurface Using Microtremor on the Ground Surface.&#8221; Proc. 20th JSCE Earthquake Eng. Symposium.

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Analysis of Antarctic glaciations by seismic reflection and refraction tomography

Marine Geology ◽

10.1016/j.margeo.2005.02.008 ◽

2005 ◽

Vol 216 (3) ◽

pp. 145-154 ◽

Cited By ~ 8

Author(s):

Flavio Accaino ◽

Gualtiero Böhm ◽

Giuliano Brancolini

Keyword(s):

Seismic Reflection ◽

Reflection And Refraction ◽

Refraction Tomography

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Neotectonic Activity in the Low-Strain Broken Foreland (Santa Bárbara System) of the North-Western Argentinean Andes (26°S)

Lithosphere ◽

10.2113/2020/8888588 ◽

2020 ◽

Vol 2020 (1) ◽

pp. 1-25

Author(s):

Ahmad Arnous ◽

Martin Zeckra ◽

Agostina Venerdini ◽

Patricia Alvarado ◽

Ramón Arrowsmith ◽

...

Keyword(s):

Electrical Resistivity ◽

Seismic Reflection ◽

Seismic Refraction ◽

Sedimentary Basins ◽

Santa Barbara ◽

Seismic Reflection Data ◽

Near Surface ◽

South Central ◽

Refraction Tomography ◽

Fault Scarps

Abstract Uplift in the broken Andean foreland of the Argentine Santa Bárbara System (SBS) is associated with the contractional reactivation of basement anisotropies, similar to those reported from the thick-skinned Cretaceous-Eocene Laramide province of North America. Fault scarps, deformed Quaternary deposits and landforms, disrupted drainage patterns, and medium-sized earthquakes within the SBS suggest that movement along these structures may be a recurring phenomenon, with yet to be defined repeat intervals and rupture lengths. In contrast to the Subandes thrust belt farther north, where eastward-migrating deformation has generated a well-defined thrust front, the SBS records spatiotemporally disparate deformation along structures that are only known to the first order. We present herein the results of geomorphic desktop analyses, structural field observations, and 2D electrical resistivity tomography and seismic-refraction tomography surveys and an interpretation of seismic reflection profiles across suspected fault scarps in the sedimentary basins adjacent to the Candelaria Range (CR) basement uplift, in the south-central part of the SBS. Our analysis in the CR piedmont areas reveals consistency between the results of near-surface electrical resistivity and seismic-refraction tomography surveys, the locations of prominent fault scarps, and structural geometries at greater depth imaged by seismic reflection data. We suggest that this deformation is driven by deep-seated blind thrusting beneath the CR and associated regional warping, while shortening involving Mesozoic and Cenozoic sedimentary strata in the adjacent basins was accommodated by layer-parallel folding and flexural-slip faults that cut through Quaternary landforms and deposits at the surface.

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Subsurface space investigation jointly using seismic reflection and refraction tomography in urban area: a case study of Hangzhou, China

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/660/1/012007 ◽

2021 ◽

Vol 660 (1) ◽

pp. 012007

Author(s):

Ziyan Fang ◽

Zhanjie Shi ◽

Jie Liu

Keyword(s):

Urban Area ◽

Seismic Reflection ◽

Reflection And Refraction ◽

Refraction Tomography

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Integration of Multi-geophysical Approaches to Identify Potential Pathways of Heavy Metals Contamination - A Case Study in Zeida, Morocco

Journal of Environmental and Engineering Geophysics ◽

10.32389/jeeg9-067 ◽

2020 ◽

Vol 25 (3) ◽

pp. 415-423

Author(s):

Ahmed Lachhab ◽

El Mehdi Benyassine ◽

Mohamed Rouai ◽

Abdelilah Dekayir ◽

Jean C. Parisot ◽

...

Keyword(s):

Heavy Metals ◽

Seismic Velocity ◽

Seismic Refraction ◽

Geophysical Methods ◽

Low Frequency ◽

Electrical Current ◽

P Wave ◽

Low Resistivity ◽

Refraction Tomography ◽

Geophysical Surveys

The tailings of Zeida's abandoned mine are found near the city of Midelt, in the middle of the high Moulouya watershed between the Middle and the High Atlas of Morocco. The tailings occupy an area of about 100 ha and are stored either in large mining pit lakes with clay-marl substratum or directly on a heavily fractured granite bedrock. The high contents of lead and arsenic in these tailings have transformed them into sources of pollution that disperse by wind, runoff, and seepage to the aquifer through faults and fractures. In this work, the main goal is to identify the pathways of contaminated water with heavy metals and arsenic to the local aquifers, water ponds, and Moulouya River. For this reason, geophysical surveys including electrical resistivity tomography (ERT), seismic refraction tomography (SRT) and very low-frequency electromagnetic (VLF-EM) methods were carried out over the tailings, and directly on the substratum outside the tailings. The result obtained from combining these methods has shown that pollutants were funneled through fractures, faults, and subsurface paleochannels and contaminated the hydrological system connecting groundwater, ponds, and the river. The ERT profiles have successfully shown the location of fractures, some of which extend throughout the upper formation to depths reaching the granite. The ERT was not successful in identifying fractures directly beneath the tailings due to their low resistivity which inhibits electrical current from propagating deeper. The seismic refraction surveys have provided valuable details on the local geology, and clearly identified the thickness of the tailings and explicitly marked the boundary between the Triassic formation and the granite. It also aided in the identification of paleochannels. The tailings materials were easily identified by both their low resistivity and low P-wave velocity values. Also, both resistivity and seismic velocity values rapidly increased beneath the tailings due to the compaction of the material and lack of moisture and have proven to be effective in identifying the upper limit of the granite. Faults were found to lie along the bottom of paleochannels, which suggest that the locations of these channels were caused by these same faults. The VLF-EM surveys have shown tilt angle anomalies over fractured areas which were also evinced by low resistivity area in ERT profiles. Finally, this study showed that the three geophysical methods were complementary and in good agreement in revealing the pathways of contamination from the tailings to the local aquifer, nearby ponds and Moulouya River.

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