scholarly journals Satellite imaging of the 2015 M7.2 earthquake in the Central Pamir, Tajikistan, elucidates a sequence of shallow strike-slip ruptures of the Sarez-Karakul fault

2020 ◽  
Vol 221 (3) ◽  
pp. 1696-1718 ◽  
Author(s):  
A Elliott ◽  
J Elliott ◽  
J Hollingsworth ◽  
G Kulikova ◽  
B Parsons ◽  
...  
Keyword(s):  
High Resolution ◽  
Structural Control ◽  
Strike Slip ◽  
Fault System ◽  
Landsat 8 ◽  
Satellite Imaging ◽  
Geomorphic Mapping ◽  
High Resolution Imagery ◽  
History Of ◽  
Causative Structure

SUMMARY On 7 December 2015, a shallow Mw 7.2 strike-slip earthquake struck the Murghab River Valley in the Central Pamirs of Tajikistan. Seismologically this event was similar to a large seismic event in 1911 whose causative fault has never been identified. We measure the displacement field of the 2015 event from satellite observations using Sentinel-1 radar interferometry, Landsat-8 optical pixel-tracking, and surface rupture mapping from high resolution SPOT-6/7 imagery to characterize the role this earthquake rupture plays in the accommodation of strain on its causative structure, the Sarez-Karakul fault. We present geomorphic mapping and interpretations of other Quaternary-active reaches of this fault system, which highlight variable rupture history of the different sections. These sections appear to be separated by inherited bedrock structural boundaries. Significantly, the reaches of the fault northeast and southwest of the 2015 rupture exhibit the freshest morphology prior to 2015, indicative of a more recent rupture than elsewhere. Using new high resolution imagery we map fresh scarps at the northern and southern ends of the Sarez-Karakul fault which may represent this 1911 rupture. To test which of these reaches could have been the source of the elusive 1911 event, we compare synthetic seismograms from three plausible fault sources determined from geomorphology, with observed seismic traces from 1911 at early recording stations throughout Europe. We find that the best fitting fault source is in fact southwest of the 2015 rupture, meaning that we have a record of three distinct recent events on the Sarez-Karakul fault system—two of them instrumentally recorded. Our mapping of these separate events reveals a correlation between their boundaries and the active and inherited thrust and suture systems that intersect the northeast striking left-lateral fault, suggesting structural control over the extents of individual ruptures on the active strike-slip fault.

Role of Basement Structural Inheritance and Strike-Slip Fault Dynamics in the Formation of the Pataz Gold Vein System, Eastern Andean Cordillera, Northern Peru

2021 ◽  
Author(s):  
Daniel Wiemer ◽  
Steffen G. Hagemann ◽  
Nicolas Thébaud ◽  
Carlos Villanes
Keyword(s):  
Structural Control ◽  
Structural Model ◽  
Gold Mineralization ◽  
Strike Slip ◽  
Fault System ◽  
Normal Faults ◽  
Vein System ◽  
Structural Inheritance ◽  
Andean Cordillera ◽  
Northern Peru

Abstract New regional- to vein-scale geologic mapping and structural analysis of the Carboniferous Pataz gold vein system (~10 Moz Au) reveal critical insights into the structural control on gold mineralization along the Eastern Andean Cordillera of northern Peru. The Pataz basement comprises continental volcanic arc and marginal to marine sedimentary rocks, which experienced intensive D2 deformation associated with Late Famatinian northeast to southwest compressive fold-and-thrust belt development. The D2 event produced an E-NE–dipping structural grain, including (1) tilted and F2 folded S1 foliations, (2) local F2 axial planar S2 foliations, and (3) subparallel D2 thrust faults. Intrusions, constituting the ca. 342 to 332 Ma (Mississippian) Pataz batholith, were emplaced along strike of the prominent Río Marañón fault and inherited the D2 basement structures, as evident in the orientation of suprasolidus magmatic flow zones and intrusive contacts within the batholith. Progressive horst-and-graben development affecting the volcanic carapace of the Pataz batholith records late syn- to postmagmatic uplift and transition into a NW-SE–extensional regime. We show that the E-NE–dipping, batholith-hosted gold vein system formed through synchronous activation of two geometric fault-fill vein types, following (1) the moderately E-NE–dipping D2 basement-inherited competency contrasts within the batholith and (2) shallow NE-dipping Andersonian footwall thrusts, during NE-directed shortening (D3a). Both geometric vein types display an early paragenetic stage (I) of quartz-pyrite, progressing texturally from hydraulic breccia into crack-seal laminated shear veins. A second (II), undeformed quartz-pyrite-sphalerite-galena paragenetic stage is observed to fill previously established dilational sites adjacent to newly formed D3b normal faults, which likely formed during regional NW-SE–extensional horst-graben development. Kinematics and relative timing indicate that, upon batholith solidification, D3a transpressional dextral strike-slip ruptures along the Río Marañón fault superimposed a lower-order Riedel-type fault system. Fluid-assisted fault activation preferentially impinged on the D2 basement-inherited competency contrasts within the batholith. Subsequent transition into a transtensional regime led to the D3b normal faulting, providing a feeder system for stage II fluid influx. The tectonic switch may be explained either by increasing tensile strain accommodation upon progressive strike-slip movement within a regional dilational jog or by larger-scale crustal relaxation of the late Gondwana margin upon final Pangea assembly. Our new structural model for the Pataz vein system evolution highlights the importance of basement structural inheritance in controlling the localization of gold mineralization along polycyclic supercontinent margins. We provide valuable insights for exploration targeting of complex vein arrays within rheologically heterogeneous host rocks.

Regional Tectonics & Structural Framework of Offshore Aceh's Andaman Sub-Basin, Northern Sumatra, Indonesia

2021 ◽  
Author(s):  
S. Clark
Keyword(s):  
High Resolution ◽  
Late Eocene ◽  
Strike Slip ◽  
Hydrocarbon Exploration ◽  
Fault System ◽  
Earth Model ◽  
The West ◽  
Structural Framework ◽  
Geochemical Models ◽  
Regional Tectonics

The three-way collision of the Indo-Australian, Eurasian and Pacific plates have resulted in Southeast Asia being the most tectonically complex region on Earth. This is particularly true for Offshore Aceh’s Andaman Sub-Basin, which has undergone complex late Eocene-Recent evolution. Despite a long history of hydrocarbon exploration and production, data scarcity in the offshore means that the Sub-Basin’s regional tectonics and structural framework have been poorly understood. Pre-1996 2D seismic data were low-fold and low-offset, however the 2019 PGS (NSMC3D) regional 3D survey imaged the entire Cenozoic sequence, enabling the delineation of a high-resolution tectonic framework for the first time. Integration of interpretations drawn from geophysical datasets with a 2019 biostratigraphy study has refined the ages of critical sequence boundaries and advanced the understanding of major structural elements. GEM™, the Geognostics Earth Model, has been used to place these interpretations in a regional tectonic and kinematic context using a series of high resolution plate animations. Andaman Sub-Basin formation initiated in response to the northward motion of India and collision with Eurasia, suturing the West Burma and Sibumasu Terranes through the middle-late Eocene. Continued northward motion of the Indo-Australian Plate resulted in further subduction along the Sunda Trench with associated oblique back-arc extension in present-day onshore and offshore Java and Sumatra. Concurrent rotation of Sundaland, with sinistral strike-slip motion along the Ranong and Khlong Mauri fault zones, resulted in the two rifting phases within the late Eocene (~40Ma) to early Oligocene in the Andaman Sub-Basin. Significant inversion events at 30Ma and 23Ma formed in response to dextral transpression associated with rotational extrusion of Indochina and Sundaland. Rapid subsidence followed the 30Ma inversion, resulting in a switch to post-rift sag and bathyal conditions during which turbidites infilled seabed topography. The onset of dextral strike slip between the West Burma Terrane along the Saigang fault system occurred at ~26Ma, causing transtension in the Andaman Sub-basin that terminated at 23Ma. At approximately 5Ma inversion and toe thrusts developed along the Sub-Basin’s southern margin due to uplift within the Barisan mountains. Refinement of the tectonic model, integrated with updated biostratigraphic and geochemical models, resulted in a revised tectono-stratigraphy for the Andaman Sub-Basin, which provides a predictive depositional model in which paleogeography and structural reactivation can be understood in a regional context.

scholarly journals Supraglacial lake bathymetry automatically derived from ICESat-2 constraining lake depth estimates from multi-source satellite imagery

2021 ◽  
Vol 15 (11) ◽  
pp. 5115-5132
Author(s):  
Rajashree Tri Datta ◽  
Bert Wouters
Keyword(s):  
High Resolution ◽  
Satellite Imagery ◽  
Landsat 8 ◽  
Lake Depth ◽  
Laser Altimeter ◽  
Spatial And Temporal Scales ◽  
Ice Cloud ◽  
Empirical Estimates ◽  
High Resolution Imagery ◽  
Surface Ice

Abstract. We introduce an algorithm (Watta) which automatically calculates supraglacial lake bathymetry and detects potential ice layers along tracks of the ICESat-2 (Ice, Cloud, and Land Elevation Satellite) laser altimeter. Watta uses photon heights estimated by the ICESat-2 ATL03 product and extracts supraglacial lake surface, bottom, and depth corrected for refraction and (sub-)surface ice cover in addition to producing surface heights at the native resolution of the ATL03 photon cloud. These measurements are used to constrain empirical estimates of lake depth from satellite imagery, which were thus far dependent on sparse sets of in situ measurements for calibration. Imagery sources include Landsat 8 Operational Land Imager (OLI), Sentinel-2, and high-resolution Planet Labs PlanetScope and SkySat data, used here for the first time to calculate supraglacial lake depths. The Watta algorithm was developed and tested using a set of 46 lakes near Sermeq Kujalleq (Jakobshavn) glacier in western Greenland, and we use multiple imagery sources (available for 45 of these lakes) to assess the use of the red vs. green band to extrapolate depths along a profile to full lake volumes. We use Watta-derived estimates in conjunction with high-resolution imagery from both satellite-based sources (tasked over the season) and nearly simultaneous Operation IceBridge CAMBOT (Continuous Airborne Mapping By Optical Translator) imagery (on a single airborne flight) for a focused study of the drainage of a single lake over the 2019 melt season. Our results suggest that the use of multiple imagery sources (both publicly available and commercial), in combination with altimetry-based depths, can move towards capturing the evolution of supraglacial hydrology at improved spatial and temporal scales.

Preliminary results on the slip history of the Pazarcik Segment of the East Anatolian Fault (Turkey): Insights from the integrated analyses of ASTER T-1 and Landsat 8 OLI multi-spectral imagery-based lithological mapping

2021 ◽  
Author(s):  
Erdem Kırkan ◽  
Gülsen Uçarkuş ◽  
Cengiz Zabcı
Keyword(s):  
Shear Zone ◽  
Fault System ◽  
Joint Analysis ◽  
Landsat 8 ◽  
Landsat 8 Oli ◽  
Band Ratio ◽  
Eastern Boundary ◽  
History Of ◽  
Basin Geometry ◽  
East Anatolian Fault

<p>Multi-spectral satellite imagery becomes a powerful tool in analyses of the earth’s surface in various aspects, including tectonic studies. There are many worldwide samples of such studies, documenting the distribution of faulting or deformation of lithological units especially in arid, semi-arid regions. The East Anatolian Shear Zone and its most prominent member, the East Anatolian Fault (EAF), is part of such a region, where the modern techniques of remote sensing can provide information on the history of this transform fault system. The EASZ and the EAF, together form the eastern boundary of the Anatolian Block, which in this study, we compare the efficiency of Advanced Space Borne Thermal Emission and Reflection Radiometer (ASTER) and Landsat-8 Operational Land Imager (OLI) images in the discrimination of lithological formations and the Pazarcik Segment of the EAF. First, we used the band combinations of 2/5/1 and 7/3/1, then 4/3-6/2-7/4 and 1/3-1/9-3/9 band ratios were independently selected in order to make an additional evaluation of the lithological discrimination for Landsat 8 OLI and ASTER T1 images, respectively. In the last stage, we used Principal Component Analysis (PCA), which provided a richer colour spectrum than the Band Combination and Band Ratio methods. The preliminary joint-analysis of these three methods allowed us to better understand the basin geometry along this part of the Pazarcik Segment. Accordingly the northern part of the Golbasi basin which hosts the Golbasi Lake, presents a rhomboidal geometry whereas the southern part is divided from the north with a wedge-shaped basin geometry. Towards southwest of the Pazarcik Segment, the Kisik River is left-laterally offset about ~4.8 km which is detectable on the band ratio images. Most critically, the image analysis highlight a geological offset along the Pazarcik Fault Segment at the Golbasi Lake side of the Hoya Formation. A left-lateral cumulative offset of ~11 km is measured along the displaced Hoya formation favouring the hypotheses of either a diachronic origin for the northern and eastern tectonic boundaries of Anatolia, among which the northern one highly exceeds the eastern boundary in terms of total slip, hence the age, or a wider shear zone where the total strain has been shared among parallel/sub-parallel segments.</p>

scholarly journals Active fault segments along the North Anatolian Fault system in the Sea of Marmara: implication for seismic hazard

2021 ◽  
Author(s):  
Luca Gasperini ◽  
Massimiliano Stucchi ◽  
Vincenzo Cedro ◽  
Mustapha Meghraoui ◽  
Gulsen Ucarkus ◽  
...  
Keyword(s):  
High Resolution ◽  
Seismic Hazard ◽  
Seismic Reflection ◽  
Strike Slip ◽  
North Anatolian Fault ◽  
Sediment Supply ◽  
Fault System ◽  
Sea Of Marmara ◽  
Seismic Reflection Data ◽  
The North

AbstractA new analysis of high-resolution multibeam and seismic reflection data, collected during several oceanographic expeditions starting from 1999, allowed us to compile an updated morphotectonic map of the North Anatolian Fault below the Sea of Marmara. We reconstructed kinematics and geometries of individual fault segments, active at the time scale of 10 ka, an interval which includes several earthquake cycles, taking as stratigraphic marker the base of the latest marine transgression. Given the high deformation rates relative to sediment supply, most active tectonic structures have a morphological expression at the seafloor, even in presence of composite fault geometries and/or overprinting due to mass-wasting or turbidite deposits. In the frame of the right-lateral strike-slip domain characterizing the North Anatolian fault system, three types of deformation are observed: almost pure strike-slip faults, oriented mainly E–W; NE/SW-aligned axes of transpressive structures; NW/SE-oriented trans-tensional depressions. Fault segmentation occurs at different scales, but main segments develop along three major right-lateral oversteps, which delimit main fault branches, from east to west: (i) the transtensive Cinarcik segment; (ii) the Central (East and West) segments; and (iii) the westernmost Tekirdag segment. A quantitative morphometric analysis of the shallow deformation patterns observed by seafloor morphology maps and high-resolution seismic reflection profiles along the entire basin allowed to determine nature and cumulative lengths of individual fault segments. These data were used as inputs for empirical relationships, to estimate maximum expected Moment Magnitudes, obtaining values in the range of 6.8–7.4 for the Central, and 6.9–7.1 for the Cinarcik and Tekirdag segments, respectively. We discuss these findings considering analyses of historical catalogues and available paleoseismological studies for the Sea of Marmara region to formulate reliable seismic hazard scenarios.

scholarly journals Clasificación de imágenes Landsat-8 en la Demarcación Hidrográfica del Segura

2019 ◽  
pp. 33
Author(s):  
M. I. Rodríguez-Valero ◽  
F. Alonso-Sarria
Keyword(s):  
Maximum Likelihood ◽  
High Resolution ◽  
Random Forest ◽  
Cross Validation ◽  
Landsat 8 ◽  
Land Uses ◽  
High Resolution Imagery ◽  
The One

<p>This work presents a cartography of land uses in the Segura Hydrographic Demarcation obtained by classifying 2017 Landsat 8 images. The classification was carried out using two classifiers: Maximum Likelihood (ML) and Random Forest (RF). Training areas were obtained from historical high resolution imagery until 2016. Prior to classification, a cross validation analysis of the training areas was carried out to determine which of them may have undergone a change of use between 2016 and 2017. The results obtained with ML and RF, both with the original set of training areas and with the one obtained eliminating the problem, are compared to determine the best option. In the case of ML, the results improve after eliminating the changing training areas, from 77.7% to 81.4%; however, with RF this improvement is not so important, going from 84.1% to 85.1%. Therefore, it can be concluded that, with both methods, the classification is more exact when the modified training areas are used and, although the results obtained are quite acceptable for both ML and RF, the latter performs a more accurate classification.</p>

scholarly journals Detecting and Quantifying a Massive Invasion of Floating Aquatic Plants in the Río de la Plata Turbid Waters Using High Spatial Resolution Ocean Color Imagery

2018 ◽  
Vol 10 (7) ◽  
pp. 1140 ◽  
Author(s):  
Ana Dogliotti ◽  
Juan Gossn ◽  
Quinten Vanhellemont ◽  
Kevin Ruddick
Keyword(s):  
High Resolution ◽  
Aquatic Plants ◽  
Color Space ◽  
Landsat 8 ◽  
Rio De La Plata ◽  
Río De La Plata ◽  
La Plata ◽  
Turbid Waters ◽  
High Resolution Imagery ◽  
Floating Vegetation

The massive development of floating plants in floodplain lakes and wetlands in the upper Middle Paraná river in the La Plata basin is environmentally and socioeconomically important. Every year aquatic plant detachments drift downstream arriving in small amounts to the Río de la Plata, but huge temporary invasions have been observed every 10 or 15 years associated to massive floods. From late December 2015, heavy rains driven by a strong El Niño increased river levels, provoking a large temporary invasion of aquatic plants from January to May 2016. This event caused significant disruption of human activities via clogging of drinking water intakes in the estuary, blocking of ports and marinas and introducing dangerous animals from faraway wetlands into the city. In this study, we developed a scheme to map floating vegetation in turbid waters using high-resolution imagery, like Sentinel-2/SMI (MultiSpectral Imager), Landsat-8/OLI (Operational Land Imager), and Aqua/MODIS (MODerate resolution Imager Spectroradiometer)-250 m. A combination of the Floating Algal Index (that make use of the strong signal in the NIR part of the spectrum), plus conditions set on the RED band (to avoid misclassifying highly turbid waters) and on the CIE La*b* color space coordinates (to confirm the visually “green” pixels as floating vegetation) were used. A time-series of multisensor high resolution imagery was analyzed to study the temporal variability, covered area and distribution of the unusual floating macroalgae invasion that started in January 2016 in the Río de la Plata estuary.

Analysis of surface rupture complexity sheds light on coseismic slip during the last earthquakes along the Bulnay-Tsetserleg fault zone (Mongolia)

2020 ◽  
Author(s):  
Yacine Benjelloun ◽  
Yann Klinger ◽  
Solène Antoine ◽  
Ganbold Baatarsuren ◽  
Laurent Bollinger ◽  
...  
Keyword(s):  
High Resolution ◽  
Satellite Imagery ◽  
Measurement Data ◽  
Fracture Network ◽  
Climatic Conditions ◽  
Strike Slip ◽  
Fault System ◽  
Northwestern Part ◽  
Coseismic Slip ◽  
Fracture Development

&lt;p&gt;In 1905, two M ~ 8 continental strike-slip earthquakes occurred along the Bulnay fault system, in the northwestern part of Mongolia. After a first earthquake that ruptured the Tsetserleg oblique fault strand, the second event ruptured the main Bulnay fault 14 days later. With a total rupture of 676 km, these two earthquakes constitute the largest continental strike-slip earthquake sequence ever documented. Hence, the Mongolian earthquake ruptures offer a unique opportunity to document large-magnitude earthquake continental ruptures. Indeed, due to dry climatic conditions, limited erosion and anthropization, the surface ruptures have been preserved almost unaltered. This allows for accurate documentation of the rupture trace and coseismic slip distribution along the Bulnay fault, based on field observation and satellite imagery.&lt;/p&gt;&lt;p&gt;Along the Tsetserleg rupture, the available coseismic offset measurement data coming from high-resolution satellite imagery show a significant variability, ranging between 1.5 and 4 m for the horizontal component. It is presently difficult to assess the most representative value for the 1905 slip, which in turn impacts the magnitude estimation for this event. Another factor to take into account is the possibility of a vertical slip component, which is only poorly constrained.&lt;/p&gt;&lt;p&gt;In order to have a better estimate of the 3D coseismic slip, drone images were acquired on selected sites along the Bulnay 1905 rupture, near the junction with Tsetserleg fault, and along the Tsetserleg rupture. We favored sites showing structural complexities and significant surface fracture development (succession of cracks and ridges, stepovers, branching zones&amp;#8230;).&lt;/p&gt;&lt;p&gt;High-resolution DEMs and orthophotomosaics were produced using the MicMac software. The geometrical characteristics of the complexities and their fracture network were then measured in order to compute the volumetric changes associated to the 1905 earthquake. These data were finally converted to 3D surface slip estimates. On certain sites, we also discussed the presence of features inherited from previous ruptures, overprinted by the 1905 earthquake.&lt;/p&gt;

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