Tectonic Motions Research Articles

Diverse early diagenetic processes of ferromanganese nodules from the eastern Pacific Ocean: evidence from mineralogy and in-situ geochemistry

ABSTRACT Ferromanganese nodules are a potential energy resource because of their high contents of economically interesting elements (i.e. Mn, Ni, Cu, and Zn). These are higher in diagenetic layers than in hydrogenetic layers. The study of the causes of elemental accumulation in the diagenetic layer is useful for the exploration metal-rich nodules. A diagenetic-dominant ferromanganese nodule, from the central Clarion–Clipperton Fracture Zone of the eastern Pacific Ocean was studied from core to rim. It was divided into four layers and seven sublayers, of the four typical diagenetic sublayers (L1, L2-1, L2-2, and L3-1). Differences were observed in these diagenetic sublayers. L1 presents the highest Mn/Fe ratio (54), the lowest Co content (2262 ppm), and a positive Ce anomaly. L2-1 exhibits high Co (3122 ppm) and Ba contents (4020 ppm), a positive Ce anomaly, and an obvious peak for 10 Å manganate minerals. L2-2 contains the lowest Ni+Cu contents (3.2 wt%), the highest Ba and Co contents (5110 ppm), and the strongest positive Ce anomaly. In L2-2, the δCe value can be positively correlated to the Mn/Fe ratio and a pronounced peak for 10 Å manganate minerals indicates that this layer has the highest mineral crystallinity. L3-1 shows the highest Ni+Cu contents (5.4 wt%), the lowest Ba (1247ppm), and Co (1725 ppm), a weakly positive Ce anomaly, and the poorest mineral crystallization. Diagenetic- and hydrogenetic-endmember mixing models reveal that hydrogenetic input contributes minimally to these chemical changes, whereas diagenetic input contributes greatly. The changes in diagenetic input may be caused by the changes in primary productivity brought about by movement of tectonic plates and the intense activity of the diagenetic pore fluid. The activity may provide a metal source for the diagenetic sublayer (anomalously high Co and Ce content) via the incorporation of metals released from dissolved buried nodules and micronodules under a suboxic or reducing environments.

Empire and Catastrophe: Decolonization and Environmental Disaster in North Africa and Mediterranean France Since 1954

Empire and Catastrophe: Decolonization and Environmental Disaster in North Africa and Mediterranean France Since 1954

ГЕОДИНАМИКА КАЛЕДОНСКОЙ БАЙКАЛО-ПАТОМСКОЙ СКЛАДЧАТОЙ ОБЛАСТИ И ЕЕ ВЛИЯНИЕ НА НЕФТЕГАЗОНОСНОСТЬ ПРЕДПАТОМСКОГО ПЕРИКРАТОННОГО ПРОГИБА

A three-dimensional geodynamical model of the Baikal-Patom folded region and associated Pre-Patom pericratonic trough was developed using materials obtained in recent years from deep seismic observations of the CDPM along the Vitim River, results of several field seasons, involving data on the deep structure of folded belts of the world as well as the results of physical modeling. Its main characteristics are thrust-underthrust character, numerous, to varying degrees reworked duplex pileups, the Caledonian age, a very high degree of denudation in the southern part, which destroyed the upper allochthonous thrust plates in the area of Lake Baikal and exposed narrow, deep, root zones, extensive development of metagenetic processes that formed tectonoclastic strata. Analogues of hydrocarbon deposits in the southern part of the pericratonic area, including such giants as the Kovyktinskoye gas condensate field, can be found further north in autochthonous basal terrigenous Vendian productive horizons under allochthonous plates. Lateral movements of large tectonic plates, fluid migration over a distance of over 200 km allow researchers to confirm the high oil-and-gas prospects of the auto- and allochthonous intervals of the sedimentary cover of the Pre-Patom petroleum area.

Investigating the Effect of Mantle Flow and Viscosity Structure on Surface Velocities in Alaska Using 3‐D Geodynamic Models

AbstractWe utilize 3‐D finite element geodynamic models, incorporating long‐term kinematic estimates of upper plate motion, to better understand the roles that viscosity structure and mantle tractions play in generating plate motions and continental interior deformation in Alaska. Surface deformation in the Pacific‐North American plate boundary zone in Alaska and northwest Canada is strongly influenced by the complex interactions between flat‐slab subduction, gravitational collapse and mantle tractions. Predictions of long‐term tectonic block motion derived from recent Global Positioning System datasets (GPS) reveal surface motions atypical of other continental convergent plate boundary zones. Specifically, in northern and northwestern Alaska, southeastward motion is observed directed back toward the plate boundary. Geodynamic models that incorporate a southeastward directed long‐wavelength mantle traction of ∼2.5–3.8 MPa best replicate surface velocities in Alaska. These mantle tractions, in conjunction with the collision of the Yakutat microplate, appear to drive the uplift and deformation in the Mackenzie Mountains. Furthermore, the extent of the northward motion in southern and central Alaska is controlled by the location of the leading edge of the Yakutat flat slab.

Bayesian Paleomagnetic Euler Pole Inversion for Paleogeographic Reconstruction and Analysis

AbstractApparent polar wander paths (APWPs) synthesized from paleomagnetic poles provide the most direct data for reconstructing past paleogeography and plate motions for times earlier than ca. 200 Ma. In this contribution, we describe a new method for APWP synthesis that extends the paleomagnetic Euler pole analysis of Gordon et al. (1984, https://doi.org/10.1029/TC003i005p00499) by placing it within the framework of a Bayesian inverse problem. This approach incorporates uncertainties in pole positions and age that are often ignored in standard treatments. The paleomagnetic Euler poles resulting from the inversions provide estimates for full‐vector plate motion (both latitude and longitude) and associated uncertainty. The method allows for inverting for one or more Euler poles with the timing of changepoints being solved as part of the inversion. In addition, the method allows the incorporation of true polar wander rotations, thus providing an avenue for probabilistic partitioning of plate tectonic motion and true polar wander based on paleomagnetic poles. We show example inversions on synthetic data to demonstrate the method's capabilities. We illustrate application of the method to Cenozoic Australia paleomagnetic poles which can be compared to independent plate reconstructions. A two‐Euler pole inversion for the Australian record recovers northward acceleration of Australia in the Eocene with rates that are consistent with plate reconstructions. We also apply the method to constrain rapid rates of motion for cratonic North America associated with the Keweenawan Track of late Mesoproterozoic paleomagnetic poles. The application of Markov chain Monte Carlo methods to estimate paleomagnetic Euler poles can open new directions in quantitative paleogeography.

Investigating the Efficiency of Deep Learning Methods in Estimating GPS Geodetic Velocity

AbstractGeodetic velocity (GV) has many applications in tectonic motion determination and geodynamic studies. Due to the high cost of global navigation satellite system stations, deep learning methods have been investigated to estimate GV. In this research, four methods of convolutional neural networks (CNNs), deep Boltzmann machines, deep belief net and recurrent neural networks have been applied. The GV of 42 global positioning system stations is entered the deep learning methods. The outputs of the four methods have successfully passed the normality test. The results show that the CNN method has a lower goodness of fit and root mean square error (RMSE). CNN can learn different dependencies and extract features.

Assessing Height Variations in Qinghai-Tibet Plateau from Time-Varying Gravity Data and Hydrological Model

Height variations caused by mass change make an important contribution to the tectonic uplift of the Qinghai-Tibet Plateau (QTP). To study the deformation attributable to hydrological loading and real potential tectonic vertical motion, satellite gravity data from the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) with data from the Global Land Data Assimilation System (GLDAS) and Global Positioning System (GPS) are adopted to estimate height variations in QTP. Based on spherical harmonic function (SHF) and Green’s function (GF), the results show the trend of height variations is unevenly distributed in the spatial domain. The SHF indicated that the rate in the southwest of the QTP is ~1 mm/year, while the northern and eastern show a subtle decreasing trend, which indicates hydrological loading is not the main cause of the uplift observed with GRACE. The maximum annual amplitude of height variations is ~12 mm, reaching the annual maximum around February to March. The average correlation coefficients of SHF, and GF height variations with GPS heights are 0.70 and 0.82, respectively. Based on cross wavelet transform, it is concluded that there are annual signals between the height variations derived from GPS with GRACE (-FO) and GLDAS. Finally, the tectonic vertical motion in the QTP is given by removing the effect of hydrological loading, which shows most GPS stations are uplifted at a rate of 0.06 mm/year–1.97 mm/year.

Determination of tectonic and nontectonic vertical motion rates of the North China Craton using dense GPS and GRACE data

• The elastic (un-)loading response to mass changes is calculated using GRACE data. • The average estimated tectonic uplift rate in the mountain areas is 1.37 ± 0.6 mm/yr. • The maximum land subsidence rate in the North China Plain is 72.0 ± 1.2 mm/yr. • A high-resolution water mass variation model is needed. Previous geodetic vertical observations show that both uplift and subsidence occur in the North China Craton. While significant land subsidence occurs in the North China Plain, uplift is observed in the surrounding mountain areas. However, previous studies neither separate the tectonic and nontectonic vertical motions nor correct for elastic response to near surface mass changes. Here, we reply on the more GPS data from 1999 to 2020 and GRACE data from 2002 to 2020 to estimate the vertical motion rates. After removing the elastic (un-)loading deformation due to near surface mass variations, we obtain the tectonic uplift rates at GPS stations built on bedrock in the mountain areas like the Shanxi Plateau and land subsidence rates mainly in the North China Plain. The tectonic rock uplift mainly occurs in the Shanxi Plateau, Yanshan Montains, Shandong Peninsula and Dabie orogen, with an average uplift rate of 1.37 ± 0.6 mm/yr, which is larger than the long-term geological uplift rate. The land subsidence mainly concentrates in the North China Plain, Shanxi Graben, and Jiangsu province with the maximum subsidence rate of 72 ± 1.2 mm/yr. The mismatch between the geodetic and geological uplift rates suggests that a high-resolution water mass loss in the North China Plain is needed.

Comparative Study on Seismic Behavior of High–Rise Steel Building with and Without Friction Damper and Fluid Viscous Damper: A Review

Abstract: Seismic forces are induced on the structure present in earthquake prone areas. These are induced due to the movement of tectonic plates. Multi-storey buildings are those that have more than two stories, hence undergo large amount of deflection due to their slender structure. Due to the deflection caused by the ground accelerations during earthquakes, the structure is unstable and the structure undergoes damage which is not safe. Passive energy dissipation devices are gaining significance in design of earthquake resistant structures because of their effective performance in controlling seismic effects on structures during earthquake. Friction dampers and fluid viscous damper are passive energy dissipating devices which are used widely as seismic control devices. The present study was conducted analytically on a 15-storey steel frame with regular and irregular configuration and performance of structure against non-linear time history ground movement with and without friction damper and fluid viscous damper. Time history ground acceleration data of Bhuj earthquake (2001) were applied on the structure and the response of friction damper and fluid viscous damper was analyzed and compared. The analysis of the structure for the non-linear dynamic ground acceleration was conducted using ETABS software. The results show that when a friction damper is used instead of a fluid viscus damper, storey displacement is greatly reduced by 25.52%. whereas results shows that storey shear, storey drift, and storey acceleration are greatly reduced by 27.75%, 30.39% and 15.27%, when fluid viscous damper is used instead of a friction damper.

Reworking of ancient tectonic amalgamation belt beneath the central north of North China Craton revealed by dense seismic observations

The North China Craton (NCC) is one of the oldest cratons in the world, and its internal tectonic belt is often used to investigate the earth’s tectonic evolution events. During the late Mesozoic and Cenozoic, the western Pacific subduction zone caused the restructuring of NCC by damaging the craton beneath eastern NCC, resulting in the distinct lateral differences between western and eastern NCC, which ultimately formed the current NCC. Furthermore, the subsequent tectonic events activated the ancient tectonic weak zones, and their traces are imprinted in the deep earth. Here, we investigated the crust structures with a high-density seismic array beneath the splice position of the eastern margin of the Khondalite Belt and the northern part of the central orogenic belt in NCC. The array included 140 short-period seismographs spaced at 2–3 km intervals, which recorded teleseismic three-component waveforms over a one-month period. P-wave receiver functions calculated from 25 teleseismic events provided an image of the crustal structure. The weak Moho and Moho offset under the study area are visible in the migration image of receiver functions. The geological investigations and the rock outcrops were combined to establish the strong coupling relationship between the present surface fault-depression system and deep structures. The deep material circulation, which governs the surface extension of the basin-range structure, is controlled by the deep material circulation which is ultimately derived from the continuous subduction of the western Pacific. The study’s findings indicate that the ancient amalgamative belt might have transformed into a weak zone easily susceptible to modification by plate tectonic movements.

High pressure-temperature phase equilibrium studies on Martian basalts: Implications for the failure of plate tectonics on Mars

Mars lacks ongoing tectonic activities such as volcanism and mountain-building processes. Modern plate tectonic movements on the Earth's surface are driven primarily by the descent of subducted slabs into the mantle. Slab crust made of dense eclogite metamorphosed from the Mid-Ocean Ridge Basalt provides an important driving force for slab subduction. Thus, mantle convection inside Mars can be hindered if the density contrast between Martian slab crust and the ambient Martian mantle is sufficiently smaller than that of Earth. To evaluate this hypothesis, we carried out high pressure-temperature phase equilibrium experiments on three different Martian basalts: Yamato 980459, NWA 8159, and GUSEV basalt (Humphrey). The GUSEV basalt and NWA 8159 undergo partial or complete melting along the Martian areotherm due to their high Fe content, suggesting that both compositions are geochemically evolved. Yamato 980459, the nearly primitive Martian basalt, on the other hand, would transform to a low-density eclogite at a depth of ∼250 km. The density contrast between a Martian crustal slab made of Yamato 980459, and the ambient Martian mantle is much smaller than that for Earth's mantle. Calculated slab sinking torques and velocities further suggest that sustained buoyancy-driven subduction of thin slabs was unlikely early in Martian history. Additional experiments exploring wider composition and pressure-temperature ranges are needed to fully understand the consequences of Martian mantle compositions and cooling history for the tectonic history of Mars.

Importance of continuous monitoring GPS permanent station at Multi-Parametric Geophysical Observatory (MPGO), IMPHAL, Manipur (India)

GPS measurements are precise enough to allow a determination of tectonic motion within a few years. This can be made using a network of permanent stations, dynamically defined, using an inertial reference frame that moves with the geo-center. Comparing the position of these points over time, it’s possible to compute the velocity and direction of the plate motion. The goal of this work is to describe the hypothetical tectonic motion using a network of GPS permanent stations located approximately in the center of Imphal Valley. We report data processing results of GPS measurements of crustal deformation at Imphal, Manipur. The results suggest that the site of Imphal valley is not located on the Indian plate. The site is actually located on the Burma plate. Keywords: GPS, Crustal deformation, Imphal Valley, MPGO.

Interseismic Masking of Fault Slip Deficit Rates by Earthquake Cycle Processes and Local Block Rotations

Abstract Interseismic geodetic observations at active boundaries contain information about tectonic motions and earthquake cycle processes. The combined effects of these two processes may serve to mask tectonic signals near active faults. Motivated by the observation of coseismic rotational motion during the 2016 Mw 7.8 Kaikōura New Zealand earthquake we develop idealized models for the masking of tectonic motions near blocks with local rotation poles. We show that differential interseismic velocities may reach local, rather than far field, maxima contributing to suppression of apparent slip deficit rates. This effect is most pronounced for small (<100 km) tectonic blocks with deep (>10 km) effective locking depths.

Intelligent solutions for earthquake data analysis and prediction for future smart cities

The analysis and prediction of the Earthquake for smart cities are of greatest significance because all the critical infrastructure like drinking water resources, mobile networks, healthcare, power grid, and transportation, may affect the social-economic balance of the place which is tampered with such natural disasters. An earthquake has some effect on the environment due to the sudden movement of tectonic plates known as Earthquake Environmental Effects (EEE). These changes can be divided into 2 categories namely primary (e.g. subsidence, surface faulting) and secondary effects (displaced rocks, tsunami, landslides). In this paper, the major contribution revolves around earthquakes and their analysis. Earthquakes occur due to the shifting of tectonic plates on the lithosphere. These movements occur due to the Frictional stress between gliding plate borders builds up and leads to fault line failure. This sudden shaking of the plates releases a certain kind of energy in the Lithosphere which creates seismic waves. Earthquakes are also categorized into different classes ranging from minor to great, depending on their magnitude.

Transient hydrology-induced elastic deformation and land subsidence in Australia constrained by contemporary geodetic measurements

Earth's lithospheric deformation in response to geophysical and climatic processes manifests as a wide range of spatio-temporal elastic/viscoelastic deformation, including seismic and tectonic motion, mantle flow, and climate-induced hydrologic-cyrospheric-atmospheric mass transports. We use increasingly accurate contemporary geodetic measurements, including those from GPS, Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GFO) missions, to quantify the competing processes of the hydrological cycle and geodynamics within the Australian continental lithosphere over the last two decades, 2002 to 2020. Observed precipitation and temperature anomalies reveal that anthropogenic climate change may have exerted significant impact on the terrestrial water storage (TWS) evolution in Australia, as evidenced by anomalous fluctuation during the 2010-2012 El Niño Southern Oscillation (ENSO) events. In particular, enhanced TWS inferred from the geodetic observations is shown to be highly correlated with increased precipitation during the 2010-2012 La Niña event. The GPS observed vertical land motion cannot be completely explained by the elastic deformation induced by surface water storage variations across Australia, nor by the Glacial Isostatic Adjustment (GIA) geophysical process. We suggest that the geodetic-observed land subsidence of Australia at high spatial scales could be related to anthropogenic aquifer groundwater depletion, while the long wavelength signals may be associated with reference frame error and then tectonic deformation.

Alluvium and Empire: The Archaeology of Colonial Resettlement and Indigenous Persistence on Peru's North Coast

Alluvium and Empire: The Archaeology of Colonial Resettlement and Indigenous Persistence on Peru's North Coast

Transforming between WGS84 Realizations

The World Geodetic System 1984 (WGS84) has been consistent with the International Terrestrial Reference Frame (ITRF) since 1994. After the original release of WGS84 in 1987 by the Defense Mapping Agency (since superseded by the National Geospatial-Intelligence Agency, NGA), there have been six subsequent realizations of the frame, designated WGS84 (G730), WGS84 (G873), WGS84 (G1150), WGS84 (G1674), WGS84 (G1762), and WGS84 (G2139). Users of WGS84 often fail to document metadata indicating the realization and epoch related to their data collections. As a result, when transforming between realizations or between other reference frames, the transformation can lead to incorrect results. We aim to bring awareness to the nature of WGS84 and the ambiguity in how it is defined. An internally consistent set of transformation parameters is derived that allows for transformation between the WGS84 realizations and other global reference frames while accounting for nuances and inconsistencies in the published literature. The derivations are based on existing (though not easily discoverable) information. Transformation accuracy is evaluated through comparison to other software and NGA-published GPS tracking station coordinates. After accounting for plate tectonic motion, the estimated uncertainties average ±0.03 m horizontally and ±0.08 m vertically for transformations involving all realizations other than the original WGS84. Uncertainties are at the meter level for transformations that include the original WGS84. If plate motion is ignored, the horizontal uncertainties can increase by several decimeters, depending on location within a plate.

Making PGA hazard curve in big cities of bengkulu by using USGS PSHA modified

The tectonic plate movement that limits the Indonesian territory causes frequent earthquakes because the plates have dynamic rocks properties with varying strengths. The collision of the plates causes fault zones, such as in Bengkulu, a region traversed by the Sumatran fault with a record of many earthquakes. The rapid growth and development of technology could support increased infrastructure development by considering earthquakes a major global hazard. Therefore, this study aimed to create a PGA hazard curve useful in improving infrastructure development in Bengkulu's big cities. Data were sourced from the Book of Indonesian Earthquake Hazard and Source 2017. The United States Geological States Probabilistic Seismic Hazard Analysis (USGS PSHA) software was modified regarding the Ground Motion Prediction Equation (GMPE) database. The GMPE used in this study are (1) BC Hydro (2012) updated for subduction source; (2) Campbel Bozorgnia (2014), Boore Atkinson (2014) and Chiou Young (2014) for shallow crustal source, and (3) Zhao et al. (2006) and Abrahamson et al. (2018) for intraslab, with 500, 1,000, 2,500, 5,000, and 10,000 years return periods. The results obtained using the new GMPE showed a change in the maximum acceleration. The Hazard Curve (HC) and PGA map showed that the Kepahiang and Lebong Districts have the highest PGA values of 1.8070 and 1.8433 g, respectively, for the 10,000 year return period. The lowest value was 0.297g recorded in Rejang Lebong for 500 year return period.

Current stress field and its relationship to tectonism in a coal mining district, central China, for underground coal energy exploration

Adopting 47 sets of in situ stress measurements taken at depths ranging from 417 to 1123 m in a coal mining district in central China by the overcoring method, we characterize the magnitude and orientation of the current stress field and its relationship to tectonism in this district to determine the controls on in situ stress in underground coal energy exploration and seismogeology. The measurements reveal that this district is in a relatively high horizontal stress environment. The stress regimes are generally favorable for strike-slip faulting and reverse faulting and are characterized by σH >σv >σh and σH >σh >σv, revealing that the regional stress field is absolutely dominated by horizontal tectonic stress and reflects a typical tectonic stress field type. The maximum horizontal principal stress is predominantly oriented between the ENE–WSW and WNW–ESE directions and averages nearly E–W,​ which is closely related to the tectonic plate movement and crustal deformation and agrees well with the direction derived from focal mechanism solutions and other stress indicators in and around the region. The current stress field in this district generally inherited the characteristics of the tectonic stress field in the third stage and partially retained the traces generated by the tectonic stress field in the first and second stages. In addition, the frictional parameter μm, which is calculated using the derived stress data, is used as a strong predictor to reflect the capability of the level of crustal stress accumulation. This region is in a state of critical or subcritical equilibrium, and regional faults at shallow depths have a medium to slightly high frictional strength, indicating that some well-oriented faults may theoretically approach or reach frictional equilibrium and that frictional sliding may occur.

Earth's oldest hotspot track at ca. 1.8 Ga advected by a global subduction system

The concurrence of both global orogenesis and large igneous provinces (LIPs) from 2200–1600 Ma remains enigmatic. This apparent contradiction of top-down and bottom-up geodynamics occurred during assembly of Earth's oldest-known supercontinent. We present a multidisciplinary study combining the dismembered portions of major LIP worldwide and correlate them across supercontinent Columbia to the same plume center (Xiong'er of the North China craton). The succession of LIPs is then used to trace the oldest established hotspot track associated with a pulsating plume constraining ancient plate motion. Subduction-controlled plume generation can explain mantle upwelling occurring where subducted slabs forming the supercontinent had previously sunk to the base of the mantle and advected the Xiong'er mantle plume due to return flow. Tectonic motion detected by the hotspot track can account for both those regions of the supercontinent with and without LIPs. Such historical constraints on the interaction between plumes and subduction are critical in linking bottom-up and top-down tectonic processes at the dawn of the supercontinent cycle.