MIDDLE-LATE QUATERNARY GEODYNAMICS OF CRETE, SOUTHERN AEGEAN, AND SEISMOTECTONIC IMPLICATIONS

In order to characterize and quantify the superficial deformation occurred during Middle-Late Quaternary in the Southern Aegean, we have systematicaly analyzed the major tectonic structures affecting Crete Island. They typically consist of 10 to 30 km-long dip-slip normal faults, separating carbonate and/or metamorphic massifs, in the footwall block, from loose to poorly consolidated alluvial and colluvial materials within the hanging-wall. All these faults show clear evidence of recent re-activation and trend parallel to two principal directions: WNW-ESE and NNE-SSW. Based on all available data for both onland and offshore structures (morphological and structural mapping, satellite imagery and airphotographs remote sensing as well as the analysis of seismic profiles and the investigation of marine terraces and Holocene raised notches along the island coasts), for each fault we estimate and constrain some of the principal seismotectonic parameters and particularly the fault kinematics, the cumulative amount of slip and the slip-rate. Summing up the contribution to crustal extension provided by the two major fault sets (ca. E-W and ca. N-S) we calculate both radial and tangential (i.e. perpendicular and parallel to the Hellenic Arc, respectively) long-term strain-rates. A comparison of these geologically-based values with those obtained from GPS measurements show a good agreement, therefore suggesting that the present-day crustal deformation is probably active since Middle Quaternary and mainly associated with the seismic activity of upper crustal normal faults characterized by frequent shallow moderate-to strong (Mmax = 7.0) seismic events seldom alternating with stronger (Mmax = 7.5) earthquakes occurring along blind low-angle thrust planes affecting deeper and more external sectors of the Hellenic Arc.

Download Full-text

Development of a Late Quaternary Marine Terraced Landscape during On-Going Tectonic Contraction, Crescent City Coastal Plain, California

Quaternary Research ◽

10.1006/qres.1999.2061 ◽

1999 ◽

Vol 52 (2) ◽

pp. 217-228 ◽

Cited By ~ 11

Author(s):

Michael Polenz ◽

Harvey M. Kelsey

Keyword(s):

Coastal Plain ◽

Late Quaternary ◽

Hanging Wall ◽

Thrust Fault ◽

Cascadia Subduction Zone ◽

Marine Terrace ◽

Crescent City ◽

The North ◽

Marine Terraces ◽

Tectonically Active

The Crescent City coastal plain is a low-lying surface of negligible relief that lies on the upper plate of the Cascadia subduction zone in northernmost California. Whereas coastal reaches to the north in southern Oregon and to the south near Cape Mendocino contain flights of deformed marine terraces from which a neotectonic history can be deduced, equivalent terraces on the Crescent City coastal plain are not as pronounced. Reexamination of the coastal plain revealed three late Pleistocene marine terraces, identified on the basis of subtle geomorphic boundaries and further delineated by differentiable degrees of soil development. The youngest marine terrace is preserved in the axial valley of a broad syncline, and the two older marine terraces face each other across the axial region. An active thrust fault, previously recognized offshore, underlies the coastal plain, and folding in the hanging wall of this thrust fault has dictated, through differential uplift, the depositional limits of each successive marine terrace unit. This study demonstrates the importance of local structures in coastal landscape evolution along tectonically active coastlines and exemplifies the utility of soil relative-age determinations to identify actively growing folds in landscapes of low relief.

Download Full-text

Quantifying the Epistemic Uncertainty in the Probabilistic Seismic Hazard from Two Major Faults in Western Nevada

Earthquake Spectra ◽

10.1193/080717eqs156m ◽

2018 ◽

Vol 34 (2) ◽

pp. 549-568 ◽

Cited By ~ 4

Author(s):

John G. Anderson

Keyword(s):

Distribution Function ◽

Lognormal Distribution ◽

Epistemic Uncertainty ◽

Hanging Wall ◽

Slip Rate ◽

Prediction Equation ◽

Exceedance Probability ◽

Normal Faults ◽

Logic Tree ◽

Tree Distribution

The probabilistic seismic hazards in the larger cities of western Nevada are dominated by the Mount Rose and Carson Range faults. These are normal faults; Reno and Carson City are on the hanging wall. This paper finds the sensitivity of the hazard posed by these faults to epistemic uncertainty of dip, slip rate, magnitude, and choice of ground motion prediction equation (GMPE) for an earthquake that ruptures the length of each fault. SA(0.01 s) with exceedance probability of 2% in 50 years was determined for each branch of a logic tree for those properties. This paper uses tools of probability theory to characterize this logic tree distribution with a lognormal distribution function, and to suggest an estimate of uncertainty in the mean hazard. In this case, which should not be considered general, on the hanging wall, the uncertainties in fault dip and the choice of the GMPE are the dominant contribution to the standard deviation of the lognormal distribution function. Elsewhere nearby, uncertainties in fault slip rate dominate, while at larger distances uncertainties in the magnitude dominate.

Download Full-text

Seismic reflection imaging of the low-angle Panamint Valley normal fault system, eastern California, USA

10.5194/egusphere-egu2020-5625 ◽

2020 ◽

Author(s):

Ryan Gold ◽

William Stephenson ◽

Richard Briggs ◽

Christopher DuRoss ◽

Eric Kirby ◽

...

Keyword(s):

Seismic Reflection ◽

Late Quaternary ◽

Hazard Analysis ◽

Hanging Wall ◽

Normal Fault ◽

Alluvial Fan ◽

P Wave ◽

Fault System ◽

Normal Faults ◽

High Angle

<p>A fundamental question in seismic hazard analysis is whether <30&#186;-dipping low-angle normal faults (LANFs) slip seismogenically. In comparison to more steeply dipping (45-60&#186;) normal faults, LANFs have the potential to produce stronger shaking given increased potential rupture area in the seismogenic crust and increased proximity to manmade structures built on the hanging wall. While inactive LANFs have been documented globally, examples of seismogenically active LANFs are limited. The western margin of the Panamint Range in eastern California is defined by an archetype LANF that dips west beneath Panamint Valley and has evidence of Quaternary motion. In addition, high-angle dextral-oblique normal faults displace mid-to-late Quaternary alluvial fans near the range front. To image shallow (<1 km depth), crosscutting relationships between the low- and high-angle faults along the range front, we acquired two high-resolution P-wave seismic reflection profiles. The northern ~4.7-km profile crosses the 2-km-wide Wildrose Graben and the southern ~1.1-km profile extends onto the Panamint Valley playa, ~7.5 km S of Ballarat, CA. The profile across the Wildrose Graben reveals a robust, low-angle reflector that likely represents the LANF separating Plio-Pleistocene alluvial fanglomerate and pre-Cambrian meta-sedimentary deposits. High-angle faults interpreted in the seismic profile correspond to fault scarps on Quaternary alluvial fan surfaces. Interpretation of the reflection data suggests that the high-angle faults vertically displace the LANF up to 70 m within the Wildrose Graben. Similarly, the profile south of Ballarat reveals a low-angle reflector, which appears both rotated and displaced up to 260 m by high-angle faults. These results suggest that near the Panamint range front, the high-angle faults are the dominant late Quaternary structures. We conclude that, at least at shallow (<1 km) depths, the LANF we imaged is not seismogenically active today.</p>

Download Full-text

Patterns of incision and deformation on the southern flank of the Yellowstone hotspot from terraces and topography

Geological Society of America Bulletin ◽

10.1130/b35923.1 ◽

2021 ◽

Author(s):

Daphnee Tuzlak ◽

Joel Pederson ◽

Aaron Bufe ◽

Tammy Rittenour

Keyword(s):

Late Quaternary ◽

Slip Rate ◽

Snake River Plain ◽

Fault System ◽

Snake River ◽

Normal Faults ◽

Localized Deformation ◽

Fluvial Terraces ◽

Yellowstone Hotspot ◽

River Plain

Understanding the dynamics of the greater Yellowstone region requires constraints on deformation spanning million year to decadal timescales, but intermediate-scale (Quaternary) records of erosion and deformation are lacking. The Upper Snake River drainage crosses from the uplifting region that encompasses the Yellowstone Plateau into the subsiding Snake River Plain and provides an opportunity to investigate a transect across the trailing margin of the hotspot. Here, we present a new chronostratigraphy of fluvial terraces along the lower Hoback and Upper Snake Rivers and measure drainage characteristics through Alpine Canyon interpreted in the context of bedrock erodibility. We attempt to evaluate whether incision is driven by uplift of the Yellowstone system, subsidence of the Snake River Plain, or individual faults along the river’s path. The Upper Snake River in our study area is incising at roughly 0.3 m/k.y. (300 m/m.y.), which is similar to estimates from drainages at the leading eastern margin of the Yellowstone system. The pattern of terrace incision, however, is not consistent with widely hypothesized headwater uplift from the hotspot but instead is consistent with downstream baselevel fall as well as localized deformation along normal faults. Both the Astoria and Hoback faults are documented as active in the late Quaternary, and an offset terrace indicates a slip rate of 0.25−0.5 m/k.y. (250−500 m/m.y.) for the Hoback fault. Although tributary channel steepness corresponds with bedrock strength, patterns of χ across divides support baselevel fall to the west. Subsidence of the Snake River Plain may be a source of this baselevel fall, but we suggest that the closer Grand Valley fault system could be more active than previously thought.

Download Full-text

Discovery of a Jurassic Porphyry Copper Belt, Pangui Area, Southern Ecuador

SEG Discovery ◽

10.5382/segnews.2000-43.fea ◽

2000 ◽

pp. 1-15

Author(s):

IAN R. GENDALL ◽

LUIS A. QUEVEDO ◽

RICHARD H. SILLITOE ◽

RICHARD M. SPENCER ◽

CARLOS O. PUENTE ◽

...

Keyword(s):

Porphyry Copper ◽

Hanging Wall ◽

Foreland Basin ◽

Sulfide Mineral ◽

The Philippines ◽

Normal Faults ◽

Geologic Mapping ◽

Copper Mineralization ◽

Argillic Alteration ◽

Infill Drilling

ABSTRACT Grassroots exploration has led to discovery of 10 porphyry copper prospects in the previously unexplored Jurassic arc of southeastern Ecuador. The prospects are located in steep, wet, jungle-covered terrain in the Pangui area, part of the Cordillera del Cóndor. The exploration program, initially mounted in search of gold in the Oriente foreland basin, employed panned-concentrate drainage sampling. Follow-up of the resulting anomalies utilized soil sampling combined with rock-chip sampling and geologic mapping of the restricted creek outcrops. Scout and infill drilling of two of the prospects, San Carlos and Panantza, has shown hypogene mineralization averaging 0.5 to 0.7 percent Cu overlain by thin (averaging <30 m) zones of chalcocite enrichment or oxidized copper mineralization. The prospects are centered on small, composite granocliorite to monzogranite porphyry stocks that cut the Zamora batholith or, in one case, a satellite pluton. The batholith is emplaced into Jurassic volcanosedimentary formations, which concealed Triassic extensional half-grabens before being incorporated into the Subandean fold-thrust belt along the western margin of the Oriente basin. North- and northwest-striking normal faults in the hanging wall of a major north-striking fault zone controlled the locations of most of the porphyry centers. K silicate and variably overprinted intermediate argillic alteration, containing chalcopyrite as the principal sulfide mineral, characterize the central parts of most of the porphyry prospects and grade outward to pyrite-dominated propylitic halos. Overprinted sericitic alteration is generally less widely developed, although apparently shallower erosion at the Warintza and Wawame prospects resulted in preservation of extensive pyrite-rich sericitic zones. All the prospects contain appreciable (60–250 ppm) molybdenum, but gold tenors are low except at Panantza and Wawame (~0.15 and 0.2 g/t, respectively). Supergene oxidation and chalcocite enrichment zones are immature because of inhibition by the rapid erosion prevalent in the Pangui area. Supergene profiles attain their maximum development on ridge crests but are essentially absent along major creeks. Discovery of the Pangui belt, along with other recently defined porphyry copper systems in northern Perú, Indonesia, and the Philippines, underscores yet again the efficacy of drainage geochemistry as an exploration technique in tropical and subtropical arc terranes as well as the outstanding potential for additional exposed deposits in poorly explored parts of the circum-Pacific region.

Download Full-text

Late Pleistocene extension and strike-slip in the Dead Sea Basin

Geological Magazine ◽

10.1017/s001675680400963x ◽

2004 ◽

Vol 141 (5) ◽

pp. 565-572 ◽

Cited By ~ 25

Author(s):

YUVAL BARTOV ◽

AMIR SAGY

Keyword(s):

Internal Structure ◽

Slip Rate ◽

Dead Sea ◽

Strike Slip ◽

Normal Faults ◽

Small Scale ◽

Dead Sea Basin ◽

Pull Apart Basin ◽

Western Border ◽

The Dead

A newly discovered active small-scale pull-apart (Mor structure), located in the western part of the Dead Sea Basin, shows recent basin-parallel extension and strike-slip faulting, and offers a rare view of pull-apart internal structure. The Mor structure is bounded by N–S-trending strike-slip faults, and cross-cut by low-angle, E–W-trending normal faults. The geometry of this pull-apart suggests that displacement between the two stepped N–S strike-slip faults of the Mor structure is transferred by the extension associated with the normal faults. The continuing deformation in this structure is evident by the observation of at least three deformation episodes between 50 ka and present. The calculated sinistral slip-rate is 3.5 mm/yr over the last 30 000 years. This slip rate indicates that the Mor structure overlies the currently most active strike-slip fault within the western border of the Dead Sea pull-apart. The Mor structure is an example of a small pull-apart basin developed within a larger pull-apart. This type of hierarchy in pull-apart structures is an indication for their ongoing evolution.

Download Full-text

The cryptic seismic potential of blind faults revealed by off-fault geomorphology, Pichilemu, Chile.

10.21203/rs.3.rs-86121/v1 ◽

2020 ◽

Author(s):

Julius Jara-Muñoz ◽

Daniel Melnick ◽

Anne Socquet ◽

Joaquin Cortés-Aranda ◽

Dominik Brill ◽

...

Keyword(s):

Slip Rate ◽

Active Regions ◽

Seismic Hazards ◽

Recurrence Time ◽

Diagnostic Features ◽

Seismic Potential ◽

Megathrust Earthquakes ◽

Marine Terraces ◽

Stress Changes ◽

Geomorphic Features

Abstract In seismically-active regions, mapping capable faults and estimating their recurrence time is the first step to assess seismic hazards. Fault maps are commonly based on geologic and geomorphic features evident at the surface; however, mapping blind faults and estimating their seismic potential is challenging because on-fault diagnostic features are absent. Here, we study the Pichilemu Fault in coastal Chile, unknown until it generated a M7.0 earthquake in 2010. The lack of evident surface faulting suggests a partly-hidden blind fault. Using off-fault deformed marine terraces, we estimate a slip-rate of 0.42 ± 0.04 m/ka, which when integrated with deformation estimated from satellite geodesy during the 2010 earthquake suggests a 2.5 ± 0.25 ka recurrence time for M6.6-6.9 extensional earthquakes. We propose that extension is associated with stress changes during megathrust earthquakes and accommodated by sporadic slip during upper-plate earthquakes. Our results have implications for assessing the seismic potential of cryptic faults along seismically-active coasts.

Download Full-text

IDENTIFYING FAULT ACTIVITY IN THE CENTRAL EVOIKOS GULF (GREECE)

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.16639 ◽

2018 ◽

Vol 40 (1) ◽

pp. 439 ◽

Cited By ~ 5

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.

Download Full-text

New constraints on the exhumation history of the western Tauern Window (European Alps) from thermochronology, thermokinematic modeling, and topographic analysis

International Journal of Earth Sciences ◽

10.1007/s00531-021-02094-w ◽

2021 ◽

Author(s):

Reinhard Wolff ◽

Ralf Hetzel ◽

István Dunkl ◽

Aneta A. Anczkiewicz

Keyword(s):

Hanging Wall ◽

Thermal Relaxation ◽

Slip Rate ◽

Normal Fault ◽

European Alps ◽

Valley Bottom ◽

Topographic Analysis ◽

Tauern Window ◽

History Of ◽

Exhumation History

AbstractThe Brenner normal fault bounds the Tauern Window to the west and accommodated a significant portion of the orogen-parallel extension in the Eastern Alps. Here, we use zircon (U–Th)/He, apatite fission track, and apatite (U–Th)/He dating, thermokinematic modeling, and a topographic analysis to constrain the exhumation history of the western Tauern Window in the footwall of the Brenner fault. ZHe ages from an E–W profile (parallel to the slip direction of the fault) decrease westwards from ~ 11 to ~ 8 Ma and suggest a fault-slip rate of 3.9 ± 0.9 km/Myr, whereas AFT and AHe ages show no spatial trends. ZHe and AFT ages from an elevation profile indicate apparent exhumation rates of 1.1 ± 0.7 and 1.0 ± 1.3 km/Myr, respectively, whereas the AHe ages are again spatially invariant. Most of the thermochronological ages are well predicted by a thermokinematic model with a normal fault that slips at a rate of 4.2 km/Myr between ~ 19 and ~ 9 Ma and produces 35 ± 10 km of extension. The modeling reveals that the spatially invariant AHe ages are caused by heat advection due to faulting and posttectonic thermal relaxation. The enigmatic increase of K–Ar phengite and biotite ages towards the Brenner fault is caused by heat conduction from the hot footwall to the cooler hanging wall. Topographic profiles across an N–S valley in the fault footwall indicate 1000 ± 300 m of erosion after faulting ceased, which agrees with the results of our thermokinematic model. Valley incision explains why the Brenner fault is located on the western valley shoulder and not at the valley bottom. We conclude that the ability of thermokinematic models to quantify heat transfer by rock advection and conduction is crucial for interpreting cooling ages from extensional fault systems.

Download Full-text