Postglacial faulting near Crater Lake, Oregon, and its possible association with the Mazama caldera-forming eruption

2019 ◽  
Vol 131 (9-10) ◽  
pp. 1440-1458
Author(s):  
Charles R. Bacon ◽  
Joel E. Robinson
Keyword(s):  
Crater Lake ◽  
Active Faults ◽  
Large Earthquake ◽  
Normal Displacement ◽  
Normal Faults ◽  
Caldera Collapse ◽  
Normal Extension ◽  
Slip Rates ◽  
Crater Lake National Park ◽  
Lateral Offset

Abstract Volcanoes of subduction-related magmatic arcs occur in a variety of crustal tectonic regimes, including where active faults indicate arc-normal extension. The Cascades arc volcano Mount Mazama overlaps on its west an ∼10-km-wide zone of ∼north-south–trending normal faults. A lidar (light detection and ranging) survey of Crater Lake National Park, reveals several previously unrecognized faults west of the caldera. Postglacial vertical separations measured from profiles across scarps range from ∼2 m to as much as 12 m. Scarp profiles commonly suggest two or more postglacial surface-rupturing events. Ignimbrite of the ca. 7.6 ka climactic eruption of Mount Mazama, during which Crater Lake caldera formed, appears to bury fault strands where they project into thick, valley-filling ignimbrite. Lack of lateral offset of linear features suggests principally normal displacement, although predominant left stepping of scarp strands implies a component of dextral slip. West-northwest–east-southeast and north-northwest–south-southeast linear topographic elements, such as low scarps or ridges, shallow troughs, and straight reaches of streams, suggest that erosion was influenced by distributed shear, consistent with GPS vectors and clockwise rotation of the Oregon forearc block. Surface rupture lengths (SRL) of faults suggest earthquakes of (moment magnitude) Mw6.5 from empirical scaling relationships. If several faults slipped in one event, a combined SRL of 44 km suggests an earthquake of Mw7.0. Postglacial scarps as high as 12 m imply maximum vertical slip rates of 1.5 mm/yr for the zone west of Crater Lake, considerably higher than the ∼0.3 mm/yr long-term rate for the nearby West Klamath Lake fault zone. An unanswered question is the timing of surface-rupturing earthquakes relative to the Mazama climactic eruption. The eruption may have been preceded by a large earthquake. Alternatively, large surface-rupturing earthquakes may have occurred during the eruption, a result of decrease in east-west compressive stress during ejection of ∼50 km3 of magma and concurrent caldera collapse.

Estimating the slip rates of normal faults in the Great Basin, USA

2000 ◽  
Vol 12 (3-4) ◽  
pp. 227-240 ◽  
Author(s):  
C. M. dePolo ◽  
J. G. Anderson
Keyword(s):  
Great Basin ◽  
Normal Faults ◽  
Slip Rates

Slip rates along active faults estimated with cosmic-ray–exposure dates: Application to the Bogd fault, Gobi-Altaï, Mongolia

Geology ◽  
1995 ◽  
Vol 23 (11) ◽  
pp. 1019 ◽  
Author(s):  
J. F. Ritz ◽  
E. T. Brown ◽  
D. L. Bourlès ◽  
H. Philip ◽  
A. Schlupp ◽  
...  
Keyword(s):  
Active Faults ◽  
Cosmic Ray ◽  
Slip Rates

scholarly journals Active Fault Systems in the Inner Northwest Apennines, Italy: A Reappraisal One Century after the 1920 Mw ~6.5 Fivizzano Earthquake

Geosciences ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 139
Author(s):  
Giancarlo Molli ◽  
Isabelle Manighetti ◽  
Rick Bennett ◽  
Jacques Malavieille ◽  
Enrico Serpelloni ◽  
...  
Keyword(s):  
Large Scale ◽  
Active Fault ◽  
Active Faults ◽  
Dense Network ◽  
Earthquake Fault ◽  
Slip Rates ◽  
Fault Systems ◽  
Seismological Data ◽  
Seismogenic Faults

Based on the review of the available stratigraphic, tectonic, morphological, geodetic, and seismological data, along with new structural observations, we present a reappraisal of the potential seismogenic faults and fault systems in the inner northwest Apennines, Italy, which was the site, one century ago, of the devastating Mw ~6.5, 1920 Fivizzano earthquake. Our updated fault catalog provides the fault locations, as well as the description of their architecture, large-scale segmentation, cumulative displacements, evidence for recent to present activity, and long-term slip rates. Our work documents that a dense network of active faults, and thus potential earthquake fault sources, exists in the region. We discuss the seismogenic potential of these faults, and propose a general tectonic scenario that might account for their development.

scholarly journals A Long-Term Watershed-Scale Partnership to Restore Bull Trout Across Federal, State, Private, and Historic Tribal Land Near Crater Lake National Park, Oregon

Fisheries ◽  
2018 ◽  
Vol 43 (4) ◽  
pp. 183-193 ◽  
Author(s):  
M. W. Buktenica ◽  
D. K. Hering ◽  
N. Scott ◽  
C. Lambert ◽  
J. McKee ◽  
...  
Keyword(s):  
National Park ◽  
Crater Lake ◽  
Federal State ◽  
Bull Trout ◽  
Watershed Scale ◽  
Crater Lake National Park ◽  
Tribal Land

scholarly journals Tectonic Geomorphology and Paleoseismology of the Sharkhai fault: a new source of seismic hazard for Ulaanbaatar (Mongolia)

2021 ◽  
Author(s):  
Abeer Al-Ashkar ◽  
Antoine Schlupp ◽  
Matthieu Ferry ◽  
Ulziibat Munkhuu
Keyword(s):  
Seismic Hazard ◽  
Scaling Laws ◽  
Active Faults ◽  
Seismic Hazard Assessment ◽  
Capital City ◽  
Tectonic Geomorphology ◽  
Time Interval ◽  
Coseismic Slip ◽  
Slip Rates ◽  
Large Earthquakes

Abstract. We present new constraints from tectonic geomorphology and paleoseismology along the newly discovered Sharkhai fault near the capital city of Mongolia. Detailed observations from high resolution Pleiades satellite images and field investigations allowed us to map the fault in detail, describe its geometry and segmentation, characterize its kinematics, and document its recent activity and seismic behavior (cumulative displacements and paleoseismicity). The Sharkhai fault displays a surface length of ~40 km with a slightly arcuate geometry, and a strike ranging from N42° E to N72° E. It affects numerous drainages that show left-lateral cumulative displacements reaching 57 m. Paleoseismic investigations document the faulting and deposition record for the last ~3000 yr and reveal that the penultimate earthquake (PE) occurred between 1515 ± 90 BC and 945 ± 110 BC and the most recent event (MRE) occurred after 860 ± 85 AD. The resulting time interval of 2080 ± 470 years is the first constraint on the Sharkhai fault for large earthquakes. On the basis of our mapping of the surface rupture and the resulting segmentation analysis, we propose two possible scenarios for large earthquakes with likely magnitudes between 6.4 ± 0.2 and 7.1 ± 0.2. Furthermore, we apply scaling laws to infer coseismic slip values and derive preliminary estimates of long-term slip rates between 0.2 ± 0.2 and 1.0 ± 0.5 mm/y. Finally, we propose that these original observations and results from a newly discovered fault should be taken into account for the seismic hazard assessment for the city of Ulaanbaatar and help build a comprehensive model of active faults in that region.

scholarly journals The active tectonic landscape of Lake Ohrid (FYR of Macedonia/Albania)

2014 ◽  
Vol 56 (6) ◽  
Author(s):  
Nadine Hoffmann
Keyword(s):  
Active Faults ◽  
Fault Scarp ◽  
Mass Wasting ◽  
Lake Ohrid ◽  
Slip Rates ◽  
Active Tectonic ◽  
Western Border ◽  
Wine Glass ◽  
Yugoslavian Republic ◽  
Fault Scarps

<p><span style="font-family: CMR10; font-size: medium;">The study area at the Lake Ohrid Basin is located on 693 m a.s.l. at the south-western border of the Former Yugoslavian Republic of Macedonia with Albania. It is a suitable location for neotectonic studies. It exhibits a large variety of morphological expressions associated with the seismic activity of the region. Linear bedrock fault scarps give the relief on both sides of the lake a staircase-like appearance; other features are wine-glass shaped valleys and triangular facets. These often short living features are used to identify active faults and to parameterise palaeoearthquakes (slip rates, subsidence and erosion). According to the results of fault scarp profiling a halfgraben shape of the basin is proposed with the west coast being dominated by mass wasting processes most likely triggered by seismic events.</span></p>

scholarly journals IDENTIFYING FAULT ACTIVITY IN THE CENTRAL EVOIKOS GULF (GREECE)

2018 ◽  
Vol 40 (1) ◽  
pp. 439 ◽  
Author(s):  
Th. Rondoyanni ◽  
D. Galanakis ◽  
Ch. Georgiou ◽  
I. Baskoutas
Keyword(s):  
Late Quaternary ◽  
Active Faults ◽  
Point Of View ◽  
Geological Mapping ◽  
Normal Faults ◽  
Geophysical Research ◽  
Alluvial Deposits ◽  
Moderate Seismicity ◽  
Limestone Bedrock ◽  
Topographic Relief

Geological mapping on a 1:5.000 scale and a tectonic analysis in the wider Chalkida region of the Island of Evia and the adjacent Drossia area of Central Greece, have allowed the identification of a number of active and potentially active normal faults. These faults have been formed or reactivated during the Late Quaternary, since they affect Pleistocene brackish and terrestrial deposits. Some of the faults affect the contact of the limestone bedrock with the Quaternary formations, presenting characteristic polished surfaces. The faults, in places covered by the alluvial deposits of the Chalkida plain, are also detected by geophysical research. Among the identified faults, the most important are considered the Aghios Minas- Chalkida, the Avlida and the Lefkadi active faults. The first one extends from Drossia to the Chalkida area, crossing the sea straights, and has an ENE-WSW direction and a south dip. The other two, are parallel antithetic faults oriented WNW-ESE, and bound the South Evoikos Gulf on the Greek mainland and the Evia Island respectively. The mapping and evaluation of active faults in this region of moderate seismicity, with low topographic relief and consequent absence of morphotectonic features, is especially important from a seismic hazard point of view.

scholarly journals Methodology for Earthquake Rupture Rate estimates of fault networks: example for the Western Corinth Rift, Greece

2017 ◽  
Author(s):  
Thomas Chartier ◽  
Oona Scotti ◽  
Hélène Lyon-Caen ◽  
Aurélien Boiselet
Keyword(s):  
Active Faults ◽  
Slip Rate ◽  
Seismic Hazard Assessment ◽  
System Level ◽  
Fault System ◽  
Normal Faults ◽  
Accurate Estimation ◽  
Probabilistic Seismic Hazard Assessment ◽  
Earthquake Rupture ◽  
Multiple Faults

Abstract. Modelling the seismic potential of active faults is a fundamental step of probabilistic seismic hazard assessment (PSHA). An accurate estimation of the rate of earthquakes on the faults is necessary in order to obtain the probability of exceedance of a given ground motion. Most PSHA studies consider faults as independent structures and neglect the possibility of multiple faults or fault segments rupturing simultaneously (Fault to Fault -FtF- ruptures). The latest Californian model (UCERF-3) takes into account this possibility by considering a system level approach rather than an individual fault level approach using the geological , seismological and geodetical information to invert the earthquake rates. In many places of the world seismological and geodetical information long fault networks are often not well constrained. There is therefore a need to propose a methodology relying only on geological information to compute earthquake rate of the faults in the network. In this methodology, similarly to UCERF-3, a simple distance criteria is used to define FtF ruptures and consider single faults or FtF ruptures as an aleatory uncertainty. Rates of earthquakes on faults are then computed following two constraints: the magnitude frequency distribution (MFD) of earthquakes in the fault system as a whole must follow an imposed shape and the rate of earthquakes on each fault is determined by the specific slip-rate of each segment depending on the possible FtF ruptures. The modelled earthquake rates are then confronted to the available independent data (geodetical, seismological and paleoseismological data) in order to weigh different hypothesis explored in a logic tree. The methodology is tested on the Western Corinth Rift, Greece (WCR) where recent advancements have been made in the understanding of the geological slip rates of the complex network of normal faults which are accommodating the ~15 mm/yr North-South extension. Modelling results show that geological, seismological extension rates and paleoseismological rates of earthquakes cannot be reconciled with only single fault rupture scenarios and require hypothesising a large spectrum of possible FtF rupture sets. Furthermore, in order to fit the imposed regional Gutenberg-Richter MFD target, some of the slip along certain faults needs to be accommodated either with interseismic creep or as post-seismic processes. Furthermore, individual fault’s MFDs differ depending on the position of each fault in the system and the possible FtF ruptures associated with the fault. Finally, a comparison of modelled earthquake rupture rates with those deduced from the regional and local earthquake catalogue statistics and local paleosismological data indicates a better fit with the FtF rupture set constructed with a distance criteria based on a 5 km rather than 3 km, suggesting, a high connectivity of faults in the WCR fault system.

scholarly journals Assessing the impact of sedimentation on fault spacing at the Andaman Sea spreading center

Geology ◽  
2020 ◽  
Author(s):  
Clément de Sagazan ◽  
Jean-Arthur Olive
Keyword(s):  
Active Faults ◽  
Spreading Rate ◽  
Andaman Sea ◽  
Spreading Center ◽  
Normal Faults ◽  
Mid Ocean Ridge ◽  
Plate Separation ◽  
Slow Spreading ◽  
Ocean Ridge ◽  
The Impact

The stabilizing effect of surface processes on strain localization, albeit predicted by several decades of geodynamic modeling, remains difficult to document in real tectonic settings. Here we assess whether intense sedimentation can explain the longevity of the normal faults bounding the Andaman Sea spreading center (ASSC). The structure of the ASSC is analogous to a slow-spreading mid-ocean ridge (MOR), with symmetric, evenly spaced axis-facing faults. The average spacing of faults with throws ≥100 m (8.8 km) is however large compared to unsedimented MORs of commensurate spreading rate, suggesting that sedimentation helps focus tectonic strain onto a smaller number of longer-lived faults. We test this idea by simulating a MOR with a specified fraction of magmatic plate separation (M), subjected to a sedimentation rate (s) ranging from 0 to 1 mm/yr. We find that for a given M ≥ 0.7, increasing s increases fault lifespan by ~50%, and the effect plateaus for s &gt; 0.5 mm/yr. Sedimentation prolongs slip on active faults by leveling seafloor relief and raising the threshold for breaking new faults. The effect is more pronounced for faults with a slower throw rate, which is favored by a greater M. These results suggest that sedimentation-enhanced fault lifespan is a viable explanation for the large spacing of ASSC faults if magmatic input is sufficiently robust. By contrast, longer-lived faults that form under low M are not strongly influenced by sedimentation.

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