2-D seismic trenching of colluvial wedges and faults

Sheley, David; Crosby, T.; Zhou, Min; Giacoma, Jamie; Yu, Jianhua; He, Ruiqing; Schuster, Gerard T.

doi:10.1016/s0040-1951(03)00150-1

Cited by 27 publications

(17 citation statements)

References 13 publications

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“…These results have wide potential implications since our integration of ERT with seismic tomography is innovative, while the combination of ERT and seismic reflection imaging is rare in the existing literature [ Wise et al , 2003; Ahmad et al , 2009]. Of particular relevance, VHR seismic and electrical resistivity tomography defined buried colluvial packages, which are considered diagnostic of repeated episodes of coseismic surface faulting, a trait documented so far in a very few instances in the Basin and Range Province Mercur Fault [ Morey and Schuster , 1999; Mattson , 2004], Oquirrh Fault [ Sheley et al , 2003]).…”

Section: Discussionmentioning

confidence: 99%

Detecting young, slow‐slipping active faults by geologic and multidisciplinary high‐resolution geophysical investigations: A case study from the Apennine seismic belt, Italy

Improta¹,

Ferranti²,

Martini³

et al. 2010

J. Geophys. Res.

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[1] The Southern Apennines range of Italy presents significant challenges for active fault detection due to the complex structural setting inherited from previous contractional tectonics, coupled to very recent (Middle Pleistocene) onset and slow slip rates of active normal faults. As shown by the Irpinia Fault, source of a M6.9 earthquake in 1980, major faults might have small cumulative deformation and subtle geomorphic expression. A multidisciplinary study including morphological-tectonic, paleoseismological, and geophysical investigations has been carried out across the extensional Monte Aquila Fault, a poorly known structure that, similarly to the Irpinia Fault, runs across a ridge and is weakly expressed at the surface by small scarps/warps. The joint application of shallow reflection profiling, seismic and electrical resistivity tomography, and physical logging of cored sediments has proved crucial for proper fault detection because performance of each technique was markedly different and very dependent on local geologic conditions. Geophysical data clearly (1) image a fault zone beneath suspected warps, (2) constrain the cumulative vertical slip to only 25-30 m, (3) delineate colluvial packages suggesting coseismic surface faulting episodes. Paleoseismological investigations document at least three deformation events during the very Late Pleistocene (<20 ka) and Holocene. The clue to surface-rupturing episodes, together with the fault dimension inferred by geological mapping and microseismicity distribution, suggest a seismogenic potential of M6.3. Our study provides the second documentation of a major active fault in southern Italy that, as the Irpinia Fault, does not bound a large intermontane basin, but it is nested within the mountain range, weakly modifying the landscape. This demonstrates that standard geomorphological approaches are insufficient to define a proper framework of active faults in this region. More in general, our applications have wide methodological implications for shallow imaging in complex terrains because they clearly illustrate the benefits of combining electrical resistivity and seismic techniques. The proposed multidisciplinary methodology can be effective in regions characterized by young and/or slow slipping active faults.Citation: Improta, L., et al. (2010), Detecting young, slow-slipping active faults by geologic and multidisciplinary highresolution geophysical investigations: A case study from the Apennine seismic belt, Italy,

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Section: Discussionmentioning

confidence: 99%

Detecting young, slow‐slipping active faults by geologic and multidisciplinary high‐resolution geophysical investigations: A case study from the Apennine seismic belt, Italy

Improta¹,

Ferranti²,

Martini³

et al. 2010

J. Geophys. Res.

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“…Ultra shallow seismic reflection profiles can, however, be gathered in favourable cases (Steeples et al, 1997;Hunsdale et al, 1998;Baker et al, 1999) but are rarely used in active fault survey since they need relatively more time and efforts, both during the acquisition and processing. Seismic refraction tomography can be applied to detect deformations related to faulting (e.g., Sheley et al, 2003) but generally tend to produce a smooth image of the subsurface, due to the limited azimuthal coverage of the rays. Other methods, such as magnetic or gravimetric (Benson and Mustoe, 1995) are also used in fault surveys but generally focus on large-scale anomaly.…”

Section: Introductionmentioning

confidence: 99%

“…Engineering-scale investigations, using multiple or a single geophysical technique(s), were successful for imaging active faults in both normal faulting contexts (e.g., Demanet et al, 2001;Sheley et al, 2003;Wise et al, 2003) and reverse faulting domains (e.g., Williams et al, 1995;Anderson et al, 2003). However, identification of seismogenic faults in regions characterized by slow deformation rates (b 1 mm/yr) is still a difficult task, as geomorphic markers of tectonic activity may not be preserved (Peulvast et al, 1999;Meghraoui, 2001).…”

Section: Introductionmentioning

confidence: 99%

Subsurface electrical imaging of anisotropic formations affected by a slow active reverse fault, Provence, France

Nguyen

Garambois

Chardon

et al. 2007

Journal of Applied Geophysics

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“…Seismic tomography has been used successfully at sites on the Wasatch fault (Sheley et al, 2003;Buddensiek et al, 2008); the Northern Oquirrh Mountains fault (Morey and Schuster, 1999), the Mercur fault (Mattson, 2004), and the Washington fault (this report). The field experiments involved 2D and 3D surveys and the production of seismic-reflection images and tomographic images.…”

Section: Discussionmentioning

confidence: 99%

“…Colluvial wedges are often characterized by 10%-20% slower velocities than the surrounding stratified deposits, making them attractive targets for seismic velocity tomography (Morey and Schuster, 1999;Sheley et al, 2003;Mattson, 2004;Buddensiek et al, 2008). On the other hand, high-resolution seismic reflection techniques are better suited for imaging details of wellstratified deposits that lie adjacent to the colluvial wedges (Morey and Schuster, 1999).…”

Section: Seismic Imaging In Paleoseismologymentioning

confidence: 99%

Outcrops and well logs as a practicum for calibrating the accuracy of traveltime tomograms

et al. 2015

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We have developed two case studies demonstrating the use of high-resolution seismic tomography and reflection imaging in the field of paleoseismology. The first study, of the Washington fault in southern Utah, USA, evaluated the subsurface deposits in the hanging wall of the normal fault. The second study, of the Mercur fault in the eastern Great Basin of Utah, USA, helped to establish borehole locations for sampling subsurface colluvial deposits buried deeper than those previously trenched along the fault zone. We evaluated the seismic data interpretations by comparison with data obtained by trenching and logging deposits across the Washington fault, and by drill-core sampling and video logging of boreholes penetrating imaged deposits along the Mercur fault. The seismic tomograms provided critical information on colluvial wedges and faults but lacked sufficient detail to resolve individual paleoearthquakes. IntroductionTime-space patterns of earthquake recurrence and magnitude reflect the pulse of the earthquake engine and are the primary parameters required for seismic hazard analysis of faulting (McCalpin, 2009). The pulse period indicates the recurrence interval of large earthquakes, and the pulse strength is the earthquake's magnitude. Knowing these two parameters is important for establishing earthquake risk in an inhabited region.Geologic mapping and regional geophysical surveys provide information on the locations and lengths of faults, but establishing the earthquake history requires excavating and logging unconsolidated deposits that are several hundred thousand years or fewer in age. High-resolution seismic surveys are useful in site characterization, especially prior to excavation. However, the results are commonly limited by resolution and complex stratigraphy adjacent to the faults, where vertically stacked colluvial wedges contain crucial information concerning the number and magnitudes of earthquake events represented in the subsurface deposits (e.g., Stephenson et al., 1993;Morey and Schuster, 1999;McCalpin, 2009).We present two case studies of normal faulting, in which seismic methods image faulted deposits prior to excavation. In both cases, the subsurface deposits were subsequently logged, and the results compared with the seismic interpretations. This "postmortem" cri-

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2-D seismic trenching of colluvial wedges and faults

Cited by 27 publications

References 13 publications

Detecting young, slow‐slipping active faults by geologic and multidisciplinary high‐resolution geophysical investigations: A case study from the Apennine seismic belt, Italy

Detecting young, slow‐slipping active faults by geologic and multidisciplinary high‐resolution geophysical investigations: A case study from the Apennine seismic belt, Italy

Subsurface electrical imaging of anisotropic formations affected by a slow active reverse fault, Provence, France

Outcrops and well logs as a practicum for calibrating the accuracy of traveltime tomograms

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