Synorogenic extension in the Tethyan Himalaya documented by structural studies and the Kübler index, Lachung La area, NW India

AbstractTectonic observations in the Tethyan Himalaya reveal an important extensional event that succeeds the emplacement of SW-verging nappes. A major thrust, called the Kum Tso Thrust, has been backfolded and reactivated by normal faulting associated with this event.Measurements of the Kübler index, coupled with characterization of clay-size paragenesis show the effect of normal faulting on the regional metamorphic zonation and indicate that important extension zones, like the Sarchu-Lachung La Normal Fault Zone (SLFZ), exist within the Tethyan Himalaya. Diagenetic limestones from within the SLFZ are characterized by the occurrence of mixed-layered clay phases, kaolinite and an illite with a 001 peak >0.4 Δ°2θ. This zone is bordered by two anchizonal-to-epizonal zones, where illite peaks become narrower. Further to the NE the successive appearance of biotite, chloritoid, garnet and garnet-staurolite-kyanite assemblages testifies to an increase in metamorphic grade. The cataclastic samples from the normal faults contain kaolinite, smectite and a ‘broad’ illite, indicating that extension occurs under diagenetic conditions.

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The 4 December 2015 Mw 7.1 Normal-Faulting Antarctic Plate Earthquake and Its Seismotectonic Implications

Bulletin of the Seismological Society of America ◽

10.1785/0120190249 ◽

2020 ◽

Vol 110 (3) ◽

pp. 1090-1100

Author(s):

Ronia Andrews ◽

Kusala Rajendran ◽

N. Purnachandra Rao

Keyword(s):

Body Wave ◽

Focal Depth ◽

Normal Fault ◽

Normal Faults ◽

Oceanic Plate ◽

Normal Faulting ◽

Transform Faults ◽

Wave Inversion ◽

Spreading Ridges ◽

Southeast Indian Ridge

ABSTRACT Oceanic plate seismicity is generally dominated by normal and strike-slip faulting associated with active spreading ridges and transform faults. Fossil structural fabrics inherited from spreading ridges also host earthquakes. The Indian Oceanic plate, considered quite active seismically, has hosted earthquakes both on its active and fossil fault systems. The 4 December 2015 Mw 7.1 normal-faulting earthquake, located ∼700 km south of the southeast Indian ridge in the southern Indian Ocean, is a rarity due to its location away from the ridge, lack of association with any mapped faults and its focal depth close to the 800°C isotherm. We present results of teleseismic body-wave inversion that suggest that the earthquake occurred on a north-northwest–south-southeast-striking normal fault at a depth of 34 km. The rupture propagated at 2.7 km/s with compact slip over an area of 48×48 km2 around the hypocenter. Our analysis of the background tectonics suggests that our chosen fault plane is in the same direction as the mapped normal faults on the eastern flanks of the Kerguelen plateau. We propose that these buried normal faults, possibly the relics of the ancient rifting might have been reactivated, leading to the 2015 midplate earthquake.

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A reappraisal of active tectonics along the Fethiye-Burdur trend, southwestern Turkey

10.31223/x5zc99 ◽

2021 ◽

Author(s):

Edwin Nissen ◽

Mussaver Didem Cambaz ◽

Élyse Gaudreau ◽

Andrew Howell ◽

Ezgi Karasözen ◽

...

Keyword(s):

Active Tectonics ◽

Normal Fault ◽

Recent Change ◽

Strike Slip ◽

Gravitational Potential Energy ◽

Normal Faults ◽

Normal Faulting ◽

Arrival Times ◽

Anatolian Plateau ◽

Recent Earthquakes

We investigate active tectonics in southwestern Turkey along the trend between Fethiye, near the eastern end of the Hellenic subduction zone, and Burdur, on the Anatolian plateau. Previously, regional GPS velocity data have been used to propose either (1) a NE-trending zone of strike-slip faulting coined the Fethiye-Burdur Fault Zone, or (2) a mix of uniaxial and radial extension accommodated by normal faults with diverse orientations. We test these models against the available earthquake data, updated in light of recent earthquakes at Acıpayam (20 March 2019, Mw 5.6) and Bozkurt (8 August 2019, Mw 5.8) — the largest in this region in the last two decades — and at Arıcılar (24 November 2017, Mw 5.3). Using Sentinel-1 InSAR and seismic waveforms and arrival times, we show that the Acıpayam, Bozkurt and Arıcılar earthquakes were buried ruptures on pure normal faults with subtle or indistinct topographic expressions. By exploiting ray paths shared with these well-recorded modern events, we relocate earlier instrumental seismicity throughout southwestern Turkey. We find that the 1971 Mw 6.0 Burdur earthquake likely ruptured a NW-dipping normal fault in an area of indistinct geomorphology near Salda Lake, contradicting earlier studies that place it on well-expressed faults bounding the Burdur basin. Overall, the northern Fethiye-Burdur trend is characterized by orthogonal normal faulting, consistent with radial extension and likely responsible for the distinct physiography of Turkey's 'Lake District'. The southern Fethiye-Burdur trend is dominated by ESE-WNW trending normal faulting, even though most faults evident in the topography strike NE-SW. This hints at a recent change in regional strain, perhaps related to eastward propagation of the Gökova graben into the area or to rapid subsidence of the Rhodes basin. Overall, our results support GPS-derived tectonic models that depict a mix of uniaxial and radial extension throughout southwestern Turkey, with no evidence for major, active strike-slip faults anywhere along the Fethiye-Burdur trend. Normal faulting orientations are consistent with a stress field driven primarily by contrasts in gravitational potential energy between the elevated Anatolian plateau and the low-lying Rhodes and Antalya basins.

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Potentially active normal faulting zone identified in the eastern margin of Palu City, Central Sulawesi, Indonesia

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/873/1/012071 ◽

2021 ◽

Vol 873 (1) ◽

pp. 012071

Author(s):

Anggraini Rizkita Puji ◽

Mudrik Rahmawan Daryono ◽

Danny Hilman Natawidjaja

Keyword(s):

Active Faults ◽

Digital Terrain Model ◽

Slip Rate ◽

Normal Fault ◽

Provincial Government ◽

Economic Losses ◽

Normal Faults ◽

Normal Faulting ◽

Eastern Margin ◽

Central Sulawesi

Abstract The 2018 Mw 7.5 earthquake in Palu, Central Sulawesi, resulting in ~2,000 fatalities and estimated economic losses of ~22.8 trillion Indonesian Rupiah, according to the report of BAPPENAS and Central Sulawesi Provincial-Government. Therefore, it is necessary to prevent similar disaster in the future by further detailed studies of any other potential sources that are capable of generating such hazards. Palu City is in the vast depression valley bordered by mountains in its eastern and western margins. The 2018 earthquake source is the Palukoro Fault, which runs through the western margin of onshore Palu Valley then continued under the bay. Along the eastern margin of the valley, we also identified a wide zone of many potentially active faults strands orienting N-S and NW-SE, showing predominantly normal faulting. These faults are observed from their normal fault scarps as inspected from Light Detection and Ranging Digital Terrain Model (LiDAR DTM) data with 90-cm resolution and field ground checks. The faults deformed the old terrace sediments (Late Pleistocene, ~125 kya), but it is unclear whether they also cut the Holocene young alluvial like the ruptured fault of 2018 event. Further paleoseismology investigation is then necessary to obtain further information about these potentially-active normal faults, including their slip-rate and the past ruptures.

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Seismic depth imaging of normal faulting in the southern Death Valley Basin

Geophysics ◽

10.1190/1.1444316 ◽

1998 ◽

Vol 63 (1) ◽

pp. 223-230 ◽

Cited By ~ 7

Author(s):

Sergio Chávez‐Pérez ◽

John N. Louie ◽

Sathish K. Pullammanappallil

Keyword(s):

Normal Fault ◽

Velocity Model ◽

Death Valley ◽

Normal Faults ◽

Normal Faulting ◽

Lateral Velocity ◽

Western Basin ◽

Depth Imaging ◽

Arrival Times ◽

Velocity Variations

Motivated by the need to image faults to test Cenozoic extension models for the Death Valley region of the western basin and range province, an area of strong lateral velocity variations, we examine the geometry of normal faulting in southern Death Valley by seismic depth imaging. We analyze COCORP Death Valley Line 9 to attain an enhanced image of shallow fault structure to 2.5 km depth. Previous work used standard seismic processing to infer normal faults from bed truncations, displacement of horizontal reflectors, and diffractions. We obtain a detailed velocity model by nonlinear optimization of first‐ arrival times picked from shot gathers, examine the unprocessed data for fault reflections, and use a Kirchhoff prestack depth imaging procedure to handle lateral velocity variations and arbitrary dips properly. Fault‐plane reflections reveal the listric true‐depth geometry of the normal fault at the Black Mountains range front in southern Death Valley. This is consistent with the concept of low‐angle extension in this region and strengthens its association with crustal‐scale magmatic plumbing.

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Structural studies of retroviruses: characterization of oligomeric complexes of murine and feline leukemia virus envelope and core components formed upon cross-linking.

Journal of Virology ◽

10.1128/jvi.30.1.157-165.1979 ◽

1979 ◽

Vol 30 (1) ◽

pp. 157-165 ◽

Cited By ~ 35

Author(s):

A Pinter ◽

E Fleissner

Keyword(s):

Leukemia Virus ◽

Feline Leukemia Virus ◽

Cross Linking ◽

Structural Studies ◽

Virus Envelope ◽

Core Components

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Seismicity, focal mechanism, and stress tensor analysis of the Simav region, western Turkey

Open Geosciences ◽

10.1515/geo-2020-0010 ◽

2020 ◽

Vol 12 (1) ◽

pp. 479-490

Author(s):

Ahu Kömeç Mutlu

Keyword(s):

Moment Tensor ◽

Aftershock Sequence ◽

Movement Direction ◽

Normal Faults ◽

Normal Faulting ◽

Stress Inversion ◽

Western Turkey ◽

Stress Orientations ◽

Extension Direction ◽

Inversion Analysis

AbstractThis study focuses on the seismicity and stress inversion analysis of the Simav region in western Turkey. The latest moderate-size earthquake was recorded on May 19, 2011 (Mw 5.9), with a dense aftershock sequence of more than 5,000 earthquakes in 6 months. Between 2004 and 2018, data from earthquake events with magnitudes greater than 0.7 were compiled from 86 seismic stations. The source mechanism of 54 earthquakes with moment magnitudes greater than 3.5 was derived by using a moment tensor inversion. Normal faults with oblique-slip motions are dominant being compatible with the NE-SW extension direction of western Turkey. The regional stress field is assessed from focal mechanisms. Vertically oriented maximum compressional stress (σ1) is consistent with the extensional regime in the region. The σ1 and σ3 stress axes suggest the WNW-ESE compression and the NNE-SSW dilatation. The principal stress orientations support the movement direction of the NE-SW extension consistent with the mainly observed normal faulting motions.

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Global Mapping and Analysis of the Structural Features in the Northern Smooth Plains of Mercury

10.5194/epsc2021-743 ◽

2021 ◽

Author(s):

marco cardinale ◽

Gaetano Di Achille ◽

David A.Vaz

Keyword(s):

Imaging System ◽

Structural Features ◽

Planetary Science ◽

Altimeter Data ◽

Normal Faults ◽

Laser Altimeter ◽

Volcanic Material ◽

Geological Map ◽

Dual Imaging

Orbital data from the Messenger spacecraft (1) reveal that part of the Mercury surface is covered by smooth plains, which are interpreted to be flood volcanic material across the planetary surface (2). In this work, we present a detailed geo-structural map of the northern smooth plains between&#160; latitudes 29&#176;N and 65&#176;N. Our 1:100.000-scale map is obtained semi-automatically, using an algorithm to map all scarps from a DEM (3,4) followed by visual inspection and classification in ArcGIS. We created a DEM&#160; using the raw MLA (Mercury Laser Altimeter) data (1) ,with 500 m/pix, and we used the Mercury Messenger MDIS (Mercury Dual Imaging System) (1,2) base map with 166m per pixel for the classification stage. With this approach, we mapped and characterized 51664 features on Mercury, creating a database with several morphometric attributes (e.g. length, azimuth, scarp height) which we will use to study the tectonic evolution of the smooth plains.&#160; In this way, we classified wrinkle ridges&#8217;s scarps, ghost craters, rim craters and central peaks. The morphometric parameters of the wrinkle ridges will&#160; be quantitatively analyzed, in order to characterizer the possible tectonic process that could have formed them. This map can be considered an enhancement for the north pole of the global geological map of Mercury (1, 5). &#160; References <ul> <li>Hawkins, S. E., III, et al. (2007), The Mercury Dual Imaging System on the MESSENGER spacecraft, Space Sci. Rev., 131, 247&#8211;338..&#160;</li> <li>Denevi, B. W., et al. (2013), The distribution and origin of smooth plains on Mercury, J. Geophys. Res. Planets, 118, 891&#8211;907, doi:10.1002/jgre.20075.</li> <li>Alegre Vaz, D. (2011). Analysis of a Thaumasia Planum rift through automatic mapping and strain characterization of normal faults. Planetary and Space Science, 59(11-12), 1210&#8211;1221. doi:10.1016/j.pss.2010.07.008&#160;.</li> <li>Vaz, D. A., Spagnuolo, M. G., & Silvestro, S. (2014). Morphometric and geometric characterization of normal faults on Mars. Earth and Planetary Science Letters, 401, 83&#8211;94. doi:10.1016/j.epsl.2014.05.022.</li> <li>Kinczyk, M. J., Prockter, L., Byrne, P., Denevi, B., Buczkowski, D., Ostrach, L., & Miller, E. (2019, September). The First Global Geological Map of Mercury. In EPSC-DPS Joint Meeting 2019 (Vol. 2019, pp. EPSC-DPS2019).</li> </ul>

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