North-South variation in tectonic activity along left-stepping extensional basins revealed by morphometric analysis: Gofa province, southwestern Ethiopia, East Africa

2020 ◽  
Author(s):  
Asfaw Erbello ◽  
Gerold Zeilinger ◽  
Manfred R. Strecker
Keyword(s):  
Strain Localization ◽  
Tectonic Activity ◽  
Southern Ethiopia ◽  
Climatic Data ◽  
Long Term Effects ◽  
Study Region ◽  
The North ◽  
Hypsometric Integral ◽  
Mountain Front ◽  
Channel Steepness

<p>We report on the morphotectonic characteristics in the tectonically active Southern Ethiopia Rift (SER) based on the analysis of high-resolution topographic data (12m TanDemX) and satellite imagery. The study region is a wide zone of distributed extension at the transition from the SER and the Northern Kenyan Rift and reflects the long-term effects of episodic tectonic events in the landscape.  The uplifted footwall margins of the north-south trending and left stepping ēn ēchelon basins of the SER constitute Pan-African basement rocks in the southern and central part (Chew Bahir, Mali-Dancha and part of Beto) and tectonized Miocene basalts in the north (Sawula). As such this region is an ideal location to record the tectonic characteristics of a major transition zone between two rift systems. Some of the unsolved problems in this area concern the degree of tectonic activity, spatiotemporal variations in the amount of extension, and the nature of kinematic linkage between different faults. To examine these issues, we calculated morphometric indices of river catchments along major fault-bounded blocks as proxies for tectonic activity and combined this information with structural, seismicity, and climatic data. <br>We determined basin asymmetry, hypsometric integral, mountain-front sinuosity, valley floor to valley-width-height ratio, basin shape, the range of basin form and mean slope; additionally, we calculated knickpoint distributions and channel-steepness index values from 89 sub-basins. Combined, the data suggest a significant north-south variation in extensional processes. For example, in the northern basins knickpoints are generally located in upstream areas near the channel heads. They are rare in the Mali-Dancha basin, whereas in the Chew Bahir basin a distinct distribution along the main channel is recognized from basin head to the mountain front. In the south the knickpoints are closest to the mountain front. This unique spatial arrangement of knickpoints in rivers draining the footwalls of extensional blocks in the north-south transect suggests a gradual, southward-directed shift in extensional deformation and recent tectonic activity. The normalized channel-steepness index value is generally small; however, it also exhibits a significant southward trend with higher values (i.e., tectonic activity). Additionally, the normalized channel steepness indices are higher at orthogonally interacting faults compared to neighbouring areas, suggesting strain localization. <br>Our new results suggest a northward increase in the geomorphic maturity of the analyzed sub-basins from Chew Bahir (juvenile) to Sawula (mature), which is compatible with a northward decrease in tectonic activity and a dominance of erosional processes. This is consistent with published, northward-decreasing extension rates and the degree of regional seismicity. Furthermore, strain localization at interacting faults suggests kinematic linkage of the left-stepping bounding faults of the sub-basins.</p>

scholarly journals Piedmont deposits as seismic energy dissipators, Sierras Pampeanas of Argentina

2021 ◽  
Vol 3 (12) ◽  
Author(s):  
Adolfo Antonio Gutiérrez ◽  
Ricardo Mon ◽  
Ahmad Arnous ◽  
Rodolfo Germán Aranda-Viana
Keyword(s):  
Seismic Energy ◽  
Tectonic Activity ◽  
Study Region ◽  
Sierras Pampeanas ◽  
The North ◽  
Neotectonic Deformation ◽  
Drainage Channels ◽  
Energy Dissipators ◽  
Energy Dissipated ◽  
Fault Scarps

AbstractThis study shows the neotectonic deformation occurred in the southern piedmont of the Cumbres Calchaquíes, in the Amaicha and Tafí valleys. Neotectonic deformation manifests itself through faults, folds and diversions of drainage channels. The Amaicha valley is bounded to the north by the Tafí del Valle fault and to the south by the Los Cardones fault. The Cumbres Calchaquíes ride over the Sierra de Aconquija through the Los Cardones and Carapunco faults. The Carapunco fault also has a synestral component, responsible for generating an imbricated system of contractional fractures. In the study region many earthquakes of ≥ 3 and ≥ 4 magnitude coincide with regional faults evidencing its neotectonic activity. The seismic energy dissipated through materials with less cohesion that form the fill of the valleys, generating discrete fault scarps and strongly folded conglomerate strata. The foothills deposits of the Cumbres Calchaquíes absorbed most of the seismic energy released during the reactivation of the faults. Tectonic activity is deforming 630 a BP deposits in the Cumbres Calchaquíes piedmont.

scholarly journals Earthquake hazard potential along the Panjal Thrust and the Zanskar Thrust, NW Himalaya

2020 ◽  
Author(s):  
Bikram Singh Bali ◽  
Ahsan Afzal Wani
Keyword(s):  
Tectonic Activity ◽  
Asymmetry Factor ◽  
Kashmir Valley ◽  
Nw Himalaya ◽  
Geomorphic Indices ◽  
The North ◽  
Hypsometric Integral ◽  
Moderate Earthquake ◽  
Kashmir Basin ◽  
Extreme North

Abstract Kashmir basin is considered to be tectonically active where damaging earthquakes (historical and instrumental) and landslides have occurred. These geologic catastrophes make Kashmir valley prone to hazards. The fault bound Kashmir basin is marked by two mountain fronts: MF1 associated with the Panjal Thrust (PT) and Balapor Fault (BF) and MF2 associated with the Zanskar Thrust. These two structural units make Kashmir valley very susceptible to earthquakes. With this in view the whole basin was divided into 22 sub-basins. However only nine extreme north and south sub basins (five extreme southern and four northern extreme north) were studied to carry out relative tectonic activity of these two tectonic units. With the help of K-mean clustering of eight basin-related geomorphic indices (Hypsometric integral (Hi), Asymmetry factor (Af), Mountain front sinuosity (Smf), Basin shape (Circularity ratio (KA) and Elongation ratio (Eb)), Form factor (Ff), Bifurcation ratio (Rb) and Sinuosity index (Si) were calculated. The results of the geomorphic indices were correlated with the structural and seismic data after that they were grouped into low three (Class1), moderate (class2) and high (class3) relative tectonic activity zones based on the quantified geomorphic indices, earthquake data, structural data and field observations. The overall results infer the tectonic activity dies out towards the north of the Kashmir Valley. It was observed that the highest tectonic activity mostly corresponds to the sub basins in vicinity of the PT and BF stretching 100 Km from Shopian to Baramulla. The least tectonic activity was found to be associated with the ZT lying to the north and northeast part of the Kashmir Valley. The seismic frequency and the overall data analysis infer that the south and Southwestern side of the Kashmir has potential of moderate earthquake in future.

scholarly journals Variable Thrust Rates of the Eastern Qilianshan Mountain Front, Northeastern Margin of the Tibet Plateau and Its Implication to the Topography of the Yongchangnan Shan

2021 ◽  
Vol 9 ◽  
Author(s):  
Lei Jinghao ◽  
Li Youli ◽  
Ren Zhikun ◽  
Hu Xiu ◽  
Xiong Jianguo ◽  
...  
Keyword(s):  
Slip Rate ◽  
Strike Slip ◽  
Tibet Plateau ◽  
The Tibetan Plateau ◽  
The West ◽  
Slip Rates ◽  
Study Region ◽  
The North ◽  
Mountain Front ◽  
The Tibet Plateau

It is commonly assumed a thrust has a constant slip and uplifting rate along strike, however, this simplified model cannot always be consistent with field observations. The along strike slip patterns with variable offsets and rates contain plenty of information about the characteristics of the faulting behavior and its relationship with adjacent faults. The east Qilian Shan, located at the northeastern margin of the Tibetan Plateau, provides us an excellent opportunity to study the faulting behavior in a thrust-bounded range area. Besides the previously reported slip rates of the N-W trending tectonics across the region, we augmented the data by surveying the Fengle fault (FF), one of the north bounding thrusts of the Yongchangnan Shan. Another north bounding fault is the Kangningqiao Fault (KNF), east of the FF. Based on the vertical offsets and rates along the fault, we constructed the slip pattern along strike. The results show the vertical slip rate of the FF ranges from 0.7 ± 0.1 mm/a to 2.8 ± 1.3 mm/a across three surveyed sites. The slip rate decreases from the east to the west. The FF and KNF might be inferred as two segments of a single segmented thrust controlling the uplift of the Yongchangnan Shan. By comparing the uplift onsets in the study region, we discuss the northeastward propagated deformation along the northeastern margin of the Tibet plateau.

Preliminary detrital zircon U-Pb Geochronology of the Wasatch Formation, Powder River Basin, Wyoming

2019 ◽  
Vol 56 (3) ◽  
pp. 247-266
Author(s):  
Ian Anderson ◽  
David H. Malone ◽  
John Craddock
Keyword(s):  
River Basin ◽  
Detrital Zircon ◽  
Middle Part ◽  
Detrital Zircons ◽  
Powder River Basin ◽  
Zircon Age ◽  
Lower Eocene ◽  
The North ◽  
Mountain Front ◽  
Fluvial Sandstone

The lower Eocene Wasatch Formation is more than 1500 m thick in the Powder River Basin of Wyoming. The Wasatch is a Laramide synorgenic deposit that consists of paludal and lacustrine mudstone, fluvial sandstone, and coal. U-Pb geochronologic data on detrital zircons were gathered for a sandstone unit in the middle part of the succession. The Wasatch was collected along Interstate 90 just west of the Powder River, which is about 50 km east of the Bighorn Mountain front. The sandstone is lenticular in geometry and consists of arkosic arenite and wacke. The detrital zircon age spectrum ranged (n=99) from 1433-2957 Ma in age, and consisted of more than 95% Archean age grains, with an age peak of about 2900 Ma. Three populations of Archean ages are evident: 2886.6±10 Ma (24%), 2906.6±8.4 Ma (56%) and 2934.1±6.6 Ma (20%; all results 2 sigma). These ages are consistent with the age of Archean rocks exposed in the northern part of the range. The sparse Proterozoic grains were likely derived from the recycling of Cambrian and Carboniferous strata. These sands were transported to the Powder River Basin through the alluvial fans adjacent to the Piney Creek thrust. Drainage continued to the north through the basin and eventually into the Ancestral Missouri River and Gulf of Mexico. The provenance of the Wasatch is distinct from coeval Tatman and Willwood strata in the Bighorn and Absaroka basins, which were derived from distal source (>500 km) areas in the Sevier Highlands of Idaho and the Laramide Beartooth and Tobacco Root uplifts. Why the Bighorn Mountains shed abundant Eocene strata only to the east and not to the west remains enigmatic, and merits further study.

scholarly journals Assessing the Sensitivity of Main Crop Yields to Climate Change Impacts in China

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 172
Author(s):  
Yuan Xu ◽  
Jieming Chou ◽  
Fan Yang ◽  
Mingyang Sun ◽  
Weixing Zhao ◽  
...  
Keyword(s):  
Climate Change ◽  
Crop Yield ◽  
Food Production ◽  
Crop Yields ◽  
Climatic Factors ◽  
Climatic Data ◽  
The South ◽  
The North ◽  
Output Elasticity ◽  
The Impact

Quantitatively assessing the spatial divergence of the sensitivity of crop yield to climate change is of great significance for reducing the climate change risk to food production. We use socio-economic and climatic data from 1981 to 2015 to examine how climate variability led to variation in yield, as simulated by an economy–climate model (C-D-C). The sensitivity of crop yield to the impact of climate change refers to the change in yield caused by changing climatic factors under the condition of constant non-climatic factors. An ‘output elasticity of comprehensive climate factor (CCF)’ approach determines the sensitivity, using the yields per hectare for grain, rice, wheat and maize in China’s main grain-producing areas as a case study. The results show that the CCF has a negative trend at a rate of −0.84/(10a) in the North region, while a positive trend of 0.79/(10a) is observed for the South region. Climate change promotes the ensemble increase in yields, and the contribution of agricultural labor force and total mechanical power to yields are greater, indicating that the yield in major grain-producing areas mainly depends on labor resources and the level of mechanization. However, the sensitivities to climate change of different crop yields to climate change present obvious regional differences: the sensitivity to climate change of the yield per hectare for maize in the North region was stronger than that in the South region. Therefore, the increase in the yield per hectare for maize in the North region due to the positive impacts of climate change was greater than that in the South region. In contrast, the sensitivity to climate change of the yield per hectare for rice in the South region was stronger than that in the North region. Furthermore, the sensitivity to climate change of maize per hectare yield was stronger than that of rice and wheat in the North region, and that of rice was the highest of the three crop yields in the South region. Finally, the economy–climate sensitivity zones of different crops were determined by the output elasticity of the CCF to help adapt to climate change and prevent food production risks.

scholarly journals Increasing benthic vent formation: a threat to Japan’s ancient lake

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Michio Kumagai ◽  
Richard D. Robarts ◽  
Yasuaki Aota
Keyword(s):  
Lake Biwa ◽  
Autonomous Underwater Vehicle ◽  
Tohoku Earthquake ◽  
Water Source ◽  
Tectonic Activity ◽  
Drinking Water Source ◽  
Sudden Increase ◽  
The North ◽  
Slow Earthquakes ◽  
Near Future

AbstractAn autonomous underwater vehicle (AUV) was deployed in Lake Biwa from 2000 to 2012. In December 2009, ebullition of turbid water was first found in the deepest area (> 90 m) of the North Basin. Follow-up investigations in April and December 2010 and January 2012 confirmed the existence of benthic vents similar to the vents observed in other deep lakes. Importantly, vent numbers per unit travel distance in Lake Biwa dramatically increased from only two vents (0.37 vents km−1) in December 2009 to 54 vents (5.28 vents km−1) in January 2012, which could be related to recent tectonic activity in Japan, e.g., the M9.1 Tohoku earthquake in March 2011 and slow earthquakes along the Nankai Trough from 2006 to 2018. Continuous back-up investigations from 2014 to 2019 revealed additional benthic vents in the same area. The sudden increase in benthic vent activity (liquid and gaseous ebullitions) have significant potential to alter lake biogeochemistry and, ultimately, degrade Japan’s major drinking water source and may be a harbinger of major crustal change in the near future.

scholarly journals Anomalous azimuthal variations with 360° periodicity of Rayleigh phase velocities observed in Scandinavia

2020 ◽  
Vol 224 (3) ◽  
pp. 1684-1704
Author(s):  
Alexandra Mauerberger ◽  
Valérie Maupin ◽  
Ólafur Gudmundsson ◽  
Frederik Tilmann
Keyword(s):  
Seismic Anisotropy ◽  
Broad Band ◽  
Shear Velocity ◽  
Velocity Variation ◽  
The South ◽  
Study Region ◽  
Lithospheric Thickness ◽  
Phase Velocities ◽  
The North ◽  
Southern Norway

SUMMARY We use the recently deployed ScanArray network of broad-band stations covering most of Norway and Sweden as well as parts of Finland to analyse the propagation of Rayleigh waves in Scandinavia. Applying an array beamforming technique to teleseismic records from ScanArray and permanent stations in the study region, in total 159 stations with a typical station distance of about 70 km, we obtain phase velocities for three subregions, which collectively cover most of Scandinavia (excluding southern Norway). The average phase dispersion curves are similar for all three subregions. They resemble the dispersion previously observed for the South Baltic craton and are about 1 per cent slower than the North Baltic shield phase velocities for periods between 40 and 80 s. However, a remarkable sin(1θ) phase velocity variation with azimuth is observed for periods >35 s with a 5 per cent deviation between the maximum and minimum velocities, more than the overall lateral variation in average velocity. Such a variation, which is incompatible with seismic anisotropy, occurs in northern Scandinavia and southern Norway/Sweden but not in the central study area. The maximum and minimum velocities were measured for backazimuths of 120° and 300°, respectively. These directions are perpendicular to a step in the lithosphere–asthenosphere boundary (LAB) inferred by previous studies in southern Norway/Sweden, suggesting a relation to large lithospheric heterogeneity. In order to test this hypothesis, we carried out 2-D full-waveform modeling of Rayleigh wave propagation in synthetic models which incorporate a steep gradient in the LAB in combination with a pronounced reduction in the shear velocity below the LAB. This setup reproduces the observations qualitatively, and results in higher phase velocities for propagation in the direction of shallowing LAB, and lower ones for propagation in the direction of deepening LAB, probably due to the interference of forward scattered and reflected surface wave energy with the fundamental mode. Therefore, the reduction in lithospheric thickness towards southern Norway in the south, and towards the Atlantic ocean in the north provide a plausible explanation for the observed azimuthal variations.

scholarly journals Assessment of Resource and Forecast Modeling of Wind Speed through An Evolutionary Programming Approach for the North of Tehuantepec Isthmus (Cuauhtemotzin, Mexico)

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3197 ◽  
Author(s):  
Luis López-Manrique ◽  
E. Macias-Melo ◽  
O. May Tzuc ◽  
A. Bassam ◽  
K. Aguilar-Castro ◽  
...  
Keyword(s):  
Wind Speed ◽  
Computation Time ◽  
Ground Level ◽  
Bimodal Distribution ◽  
Programming Approach ◽  
Climatic Data ◽  
Wind Speeds ◽  
Availability Analysis ◽  
The North ◽  
Wind Resource

This work studies the characteristics of the wind resource for a location in the north zone of Tehuantepec isthmus. The study was conducted using climatic data from Cuauhtemotzin, Mexico, measured at different altitudes above the ground level. The measured data allowed establishing the profile of wind speeds as well as the analysis of its availability. Analysis results conclude that the behavior of the wind speed presents a bimodal distribution with dominant northeast wind direction (wind flow of sea–land). In addition, the area was identified as feasible for the use of low speed power wind turbines. On the other hand, the application of a new approach for very short-term wind speed forecast (10 min) applying multi-gene genetic programming and global sensitivity analysis is also presented. Using a computational methodology, an exogenous time series with fast computation time and good accuracy was developed for the forecast of the wind speed. The results presented in this work complement the panorama for the evaluation of the resource in an area recognized worldwide for its vast potential for wind power.

scholarly journals Mass mortality of Northern Map Turtles (Graptemys geographica)

2015 ◽  
Vol 129 (1) ◽  
pp. 80 ◽  
Author(s):  
Jordan Catrysse ◽  
Emily Slavik ◽  
Jonathan Choquette ◽  
Ashley E. Leifso ◽  
Christina M. Davy
Keyword(s):  
Lake Erie ◽  
Mass Mortality ◽  
Species At Risk ◽  
Long Term Effects ◽  
North Shore ◽  
The North ◽  
The Poor ◽  
Map Turtles ◽  
Graptemys Geographica

We report a mass mortality of Northern Map Turtles (Graptemys geographica [LeSueur, 1817]) on the north shore of Lake Erie, Ontario, Canada. Thirty-five dead adult females were recovered from a nesting area over a period of four weeks. Predation and boat strikes were both excluded as potential cause of death, but the actual cause could not be determined because of the poor condition of the carcasses. Other possible explanations for the mortality include poisoning, drowning, and infection with an unidentified pathogen. Mass mortality in long-lived species, such as turtles, can have long-term effects on population growth and is a cause for concern in a species at risk.

scholarly journals Geological region by multi-signal method of gravity anomaly data in central Vietnam area

2021 ◽  
Vol 62 (5) ◽  
pp. 43-54
Author(s):  
Hong Thi Phan ◽  
Petrov Aleksey Vladimirovich ◽  
Phuong Minh Do ◽  
Luu Truong Nguyen ◽  
Keyword(s):  
Central Area ◽  
Tectonic Activity ◽  
Horizontal Gradient ◽  
Spectral Correlation ◽  
Sliding Windows ◽  
The North ◽  
Central Vietnam ◽  
Two Dimensional Filtering ◽  
Calculation Results ◽  
Signal Method

This paper presents the research results of applying the combined method of probabilistic statistical approaches, energy density spectral correlation, two-dimensional filtering in dynamic sliding windows, full horizontal gradient and heterogeneous axis tracking method to process and interpret the Bughe gravitational anomaly field in central area Vietnam. The calculation results have shown the superiority of the twodimensional filter in dynamic sliding windows compared to the filters in fixed windows in GEOSOFT software, GMT software. According to the physical characteristics of the field, the study area was divided into 13 homogeneous classes, this result is consistent with the geological-tectonic data in the area. In the north and northeast, the stabilized rock layers are characterized by homogeneous layers that extend in the northwestsoutheast direction. In the south and southwest, there is complex tectonic activity characterized by high density rock layers overlain by low density rock layers in each fault band with different directions of development. This suggests that there may be deeply buried mineral deposits of magmatic origin in central area Vietnam.

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