The Portland Hills Fault: uncovering a hidden fault in Portland, Oregon using high-resolution geophysical methods

Liberty, Lee M.; Hemphill‐Haley, Mark; Madin, Ian P.

doi:10.1016/s0040-1951(03)00152-5

Cited by 35 publications

(22 citation statements)

References 16 publications

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“…In a wider context, the multidisciplinary and scale‐based investigation strategy used in this study can be effective to detect properly young and/or slow‐slipping active normal faults, in regions where geological and environmental conditions are unfavorable to the preservation of short‐term tectonic indicators (Rhine Graben [ Megharoui et al , 2000], Andean Precordillera of Western Argentina [ Fazzito et al , 2009], Central Andes [ Cabrera and Sebrier , 1998; Schoenbohm and Strecker , 2009], Thessaly in Greece [ Caputo , 1995]), as well as in urbanized areas [ Dolan and Pratt , 1997; Liberty et al , 2003]. …”

Section: Discussionmentioning

confidence: 99%

“…In such a context, a geological approach based on traditional geomorphic and structural observations is often insufficient for the characterization of active faults (see Pantosti and Valensise [1990] for a discussion). On the contrary, multidisciplinary strategies integrating field studies, paleoseismological investigations and shallow geophysical imaging are required for the definition of a proper framework of active faults [ Meghraoui et al , 2000; Liberty et al , 2003]. …”

Section: Introductionmentioning

confidence: 99%

“…The white dashed circles denote the Sannio-Irpinia boundary (SIB) and the Val d'Agri (VA) region, corresponding to major seismic gaps in the instrumental catalogs [Castello et al, 2006]. required for the definition of a proper framework of active faults [Meghraoui et al, 2000;Liberty et al, 2003].…”

Section: Introductionmentioning

confidence: 99%

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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%

Section: Introductionmentioning

confidence: 99%

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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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show abstract

“…High-resolution ground-penetrating radar (GPR) surveying provides a means to image shallow complex structures not evident at the surface (e.g. Smith and Jol, 1995;Yetton and Nobes, 1998;Green et al, 2003;Liberty et al, 2003;Gross et al, 2004;Tronicke et al, 2006;McClymont et al, 2008aMcClymont et al, , 2008b.…”

Section: Introductionmentioning

confidence: 99%

Shallow fault segmentation of the Alpine fault zone, New Zealand revealed from 2- and 3-D GPR surveying

McClymont

Green

Kaiser

et al. 2010

Journal of Applied Geophysics

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“…Second, the data acquired with these methods are relatively easy to process and interpret if the geology is not too complex (e.g., isotropic and homogeneous layers, simple fault geometry). High resolution seismic reflection is also used when moderate to deep information is required (e.g., Shields et al, 1997;Arsdale et al, 1998;Liberty et al, 2003), since the first tens of meter, which are crucial to locate trenches for paleoseismological study, are usually poorly resolved due to the high attenuation induced by shallow sedimentary layers or by weathering (Feroci et al, 2000;Musil et al, 2002). 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.…”

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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The Portland Hills Fault: uncovering a hidden fault in Portland, Oregon using high-resolution geophysical methods

Cited by 35 publications

References 16 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

Shallow fault segmentation of the Alpine fault zone, New Zealand revealed from 2- and 3-D GPR surveying

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

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