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Vanneste, Krıs; Verbeeck, K.; Camelbeeck, Thierry; Paulissen, Étienne; Meghraoui, Mustapha; Renardy, François; Jongmans, Denis; Frechen, Manfred

doi:10.1023/a:1011419408419

Cited by 52 publications

(5 citation statements)

References 18 publications

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“…However, active tectonism in rifts is also accompanied by simultaneous erosion and degradation of fault scarps and rift-shoulder areas, with the subsiding graben providing accommodation space for the resulting sedimentary and volcanic deposits. If volcanic activity is intense and the rates of erosion and sedimentation high, or if the rate of extension is very low, the manifestations of extensional processes can be masked by erosion of fault scarps and by draping of the sedimentary and volcanic units over the various fault generations (Kübler et al, 2018;McCalpin, 2005;Vanneste et al, 2001). Examples of the masking of long-term tectonic processes are the Rio Grande Rift, which has a very low extension rate of ∼0.12 mm yr −1 (Ricketts et al, 2014) and Iceland, which has a relatively high extension rate (∼2 cm yr −1 ), but is affected by glacial overprint.…”

mentioning

confidence: 99%

Mid‐Pleistocene to Recent Crustal Extension in the Inner Graben of the Northern Kenya Rift

Riedl

Melnick

Njue³

et al. 2022

Geochem Geophys Geosyst

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Magmatic continental rifts often constitute nascent plate boundaries, yet long‐term extension rates and transient rate changes associated with these early stages of continental breakup remain difficult to determine. Here, we derive a time‐averaged minimum extension rate for the inner graben of the Northern Kenya Rift (NKR) of the East African Rift System for the last 0.5 m.y. We use the TanDEM‐X science digital elevation model to evaluate fault‐scarp geometries and determine fault throws across the volcano‐tectonic axis of the inner graben of the NKR. Along rift‐perpendicular profiles, amounts of cumulative extension are determined, and by integrating four new 40Ar/39Ar radiometric dates for the Silali volcano into the existing geochronology of the faulted volcanic units, time‐averaged extension rates are calculated. This study reveals that in the inner graben of the NKR, the long‐term extension rate based on mid‐Pleistocene to recent brittle deformation has minimum values of 1.0–1.6 mm yr−1, locally with values up to 2.0 mm yr−1. A comparison with the decadal, geodetically determined extension rate reveals that at least 65% of the extension must be accommodated within a narrow, 20‐km‐wide zone of the inner rift. In light of virtually inactive border faults of the NKR, we show that extension is focused in the region of the active volcano‐tectonic axis in the inner graben, thus highlighting the maturing of continental rifting in the NKR.

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mentioning

confidence: 99%

Mid‐Pleistocene to Recent Crustal Extension in the Inner Graben of the Northern Kenya Rift

Riedl

Melnick

Njue³

et al. 2022

Geochem Geophys Geosyst

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“…Additionally, using historical imagery can prove very useful where urban development may hide previously visible fault scarps. Once a potentially active fault is identified, it is also important to consider a multifaceted approach to a paleoseismic investigation (e.g., Camelbeeck & Meghraoui, 1998; McCalpin et al., 2023; Sherrod et al., 2008; Vanneste et al., 2001). Paleoseismic trenching is a pivotal and essential method needed to verify the existence of Quaternary rupture on faults such as the XELF, and without the use of shallow geophysics (ERT) in conjunction with field mapping, we would have not been able to discern the dip and vertical separation of the fault.…”

Section: Discussionmentioning

confidence: 99%

“…These data are essential for fault‐source models in probabilistic seismic hazard analysis (PSHA) and probabilistic fault displacement hazard analysis (PFDHA) (e.g., Brune, 1968; Chartier et al., 2017; Coppersmith & Youngs, 2000; Youngs & Coppersmith, 1985; Youngs et al., 2003), which are used in the seismic risk models that inform building codes and disaster management. Consequently, the integration of multiple modern paleoseismic techniques (e.g., lidar‐derived high‐resolution topography, shallow geophysics, and paleoseismic trenching; Camelbeeck & Meghraoui, 1998; McCalpin et al., 2023; Sherrod et al., 2008; Vanneste et al., 2001) is necessary to characterize active structures in forearcs.…”

Section: Introductionmentioning

confidence: 99%

Discovery of an Active Forearc Fault in an Urban Region: Holocene Rupture on the XEOLXELEK‐Elk Lake Fault, Victoria, British Columbia, Canada

Harrichhausen,

Finley,

Morell

et al. 2023

Tectonics

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Subduction forearcs are subject to seismic hazard from upper plate faults that are often invisible to instrumental monitoring networks. Identifying active faults in forearcs therefore requires integration of geomorphic, geologic, and paleoseismic data. We demonstrate the utility of a combined approach in a densely populated region of Vancouver Island, Canada, by combining remote sensing, historical imagery, field investigations, and shallow geophysical surveys to identify a previously unrecognized active fault, the XEOLXELEK‐Elk Lake fault, in the northern Cascadia forearc, ∼10 km north of the city of Victoria. Lidar‐derived digital terrain models and historical air photos show a ∼2.5‐m‐high scarp along the surface of a Quaternary drumlinoid ridge. Paleoseismic trenching and electrical resistivity tomography surveys across the scarp reveal a single reverse‐slip earthquake produced a fault‐propagation fold above a blind southwest‐dipping fault. Five geologically plausible chronological models of radiocarbon dated charcoal constrain the likely earthquake age to between 4.7 and 2.3 ka. Fault‐propagation fold modeling indicates ∼3.2 m of reverse slip on a blind, 50° southwest‐dipping fault can reproduce the observed deformation. Fault scaling relations suggest a M 6.1–7.6 earthquake with a 13 to 73‐km‐long surface rupture and 2.3–3.2 m of dip slip may be responsible for the deformation observed in the paleoseismic trench. An earthquake near this magnitude in Greater Victoria could result in major damage, and our results highlight the importance of augmenting instrumental monitoring networks with remote sensing and field studies to identify and characterize active faults in similarily challenging environments.

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“…The scarp was already recognized by Briquet (1907) as the morphological expression at the topographic surface of tectonic activity along the NeF. Somewhat confusingly, this scarp is now known as the Bree fault scarp (Camelbeeck & Meghraoui, 1998;Vanneste et al, 2001;Vanneste et al, 2002) even though it is not related at all to the BrF as defined by Demyttenaere ten years earlier (Demyttenaere, 1989). Furthermore contrary to the vision expressed by Dusar et al (2001), the BoF does not line up with the ZuF (Dusar et al, 2001) and further to the southeast with the ElF (Stainier, 1911).…”

Section: Local Geological Structure (Fig 1a)mentioning

confidence: 95%

Reinterpretation of the Neogene sediments of the Bree Uplift, NE Belgium

Houthuys¹,

Matthijs

2020

Geol. Belg.

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The present geological map of the Flemish Region shows a small lens-shaped isolated outcrop of the Miocene Bolderberg, Diest and Kasterlee Formations, surrounded by younger formations, in an area that coincides with the tectonic Bree Uplift segment, on the southwestern border of the Roer Valley Graben in NE Limburg. The fault, bordering the segment at its SW side, had been interpreted to be tectonically active throughout the Neogene. Now, it is argued that an erroneous lithostratigraphic interpretation of the outcropping strata supported that view. Field observations of some of the outcrops and sampled drill holes show that the sediments do not belong to an Opitter member of the Bolderberg Formation, a Gruitrode Mill member of the Diest Formation and a Dorperberg member of the Kasterlee Formation, but most probably to the lower, latest Miocene or early Pliocene part of the Mol Formation and an unknown Pliocene marginal marine deposit not unlike and at about the stratigraphic position of the Poederlee Formation. That glauconiferous sand deposit, which has always been interpreted as consisting of two successive sedimentary cycles, is now accommodated in a single cycle, using the sedimentary model of deposition in a confined, backbarrier tidal basin subject to marine sand input and local stages of flow constriction and intraformational incision. Like already proposed by Rossa (1986) and Demyttenaere (1989), reprocessed seismic sections show only minor movements along the southwestern fault of the Bree Uplift since the Paleocene, and no inverse tectonic movements at all since the Middle Miocene.

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Cited by 52 publications

References 18 publications

Mid‐Pleistocene to Recent Crustal Extension in the Inner Graben of the Northern Kenya Rift

Mid‐Pleistocene to Recent Crustal Extension in the Inner Graben of the Northern Kenya Rift

Discovery of an Active Forearc Fault in an Urban Region: Holocene Rupture on the XEOLXELEK‐Elk Lake Fault, Victoria, British Columbia, Canada

Reinterpretation of the Neogene sediments of the Bree Uplift, NE Belgium

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