scholarly journals Experimental evidence for crustal control over seismic fault segmentation

Geology ◽  
2020 ◽  
Vol 48 (8) ◽  
pp. 844-848
Author(s):  
M. Lefevre ◽  
P. Souloumiac ◽  
N. Cubas ◽  
Y. Klinger
Keyword(s):  
Brittle Material ◽  
Strike Slip ◽  
Segment Length ◽  
Physical Parameters ◽  
Structural Development ◽  
Seismic Fault ◽  
Geometrical Complexity ◽  
Scaling Relationship ◽  
Earthquake Ruptures ◽  
Analogue Models

Abstract Strike-slip faults are generally described as continuous structures, while they are actually formed of successive segments separated by geometrical complexities. Although this along-strike segmentation is known to affect the overall dynamics of earthquakes, the physical processes governing the scale of this segmentation remain unclear. Here, we use analogue models to investigate the structural development of strike-slip faults and the physical parameters controlling segmentation. We show that the length of fault segments is regular along strike and scales linearly with the thickness of the brittle material. Variations of the rheological properties only have minor effects on the scaling relationship. Ratios between the segment length and the brittle material thickness are similar for coseismic ruptures and sandbox experiments. This supports a model where crustal seismogenic thickness controls fault geometry. Finally, we show that the geometrical complexity acquired during strike-slip fault formation withstands cumulative displacement. Thus, the inherited complexity impedes the formation of an ever-straighter fault, and might control the length of earthquake ruptures.

Failure Analysis Of Buried Gas Pipelines Crossing Seismic Faults

2020 ◽  
Vol 3 (2) ◽  
pp. 781-790
Author(s):  
M. Rizwan Akram ◽  
Ali Yesilyurt ◽  
A.Can. Zulfikar ◽  
F. Göktepe
Keyword(s):  
Ground Deformation ◽  
Warning System ◽  
Strike Slip ◽  
Gas Pipelines ◽  
Steel Pipes ◽  
Seismic Fault ◽  
Fault Parameters ◽  
Dip Angle ◽  
Permanent Ground Deformation ◽  
Recent Earthquakes

Research on buried gas pipelines (BGPs) has taken an important consideration due to their failures in recent earthquakes. In permanent ground deformation (PGD) hazards, seismic faults are considered as one of the major causes of BGPs failure due to accumulation of impermissible tensile strains. In current research, four steel pipes such as X-42, X-52, X-60, and X-70 grades crossing through strike-slip, normal and reverse seismic faults have been investigated. Firstly, failure of BGPs due to change in soil-pipe parameters have been analyzed. Later, effects of seismic fault parameters such as change in dip angle and angle between pipe and fault plane are evaluated. Additionally, effects due to changing pipe class levels are also examined. The results of current study reveal that BGPs can resist until earthquake moment magnitude of 7.0 but fails above this limit under the assumed geotechnical properties of current study. In addition, strike-slip fault can trigger early damage in BGPs than normal and reverse faults. In the last stage, an early warning system is proposed based on the current procedure. 

Insights into the velocity-dependent geometry and internal strain in accretionary wedges from analogue models

2017 ◽  
Vol 155 (5) ◽  
pp. 1089-1104 ◽  
Author(s):  
BIN DENG ◽  
LEI JIANG ◽  
GAOPING ZHAO ◽  
RUI HUANG ◽  
YUANBO WANG ◽  
...  
Keyword(s):  
Brittle Material ◽  
High Velocity ◽  
Frontal Zone ◽  
Volumetric Strain ◽  
Velocity Dependence ◽  
Shortening Velocity ◽  
Asymmetric Structures ◽  
Analogue Models ◽  
Velocity Of Shortening ◽  
Geometry And Kinematics

AbstractAlthough the brittle material in analogue models is characterized by a linear Navier-Coulomb behaviour and rate-independent deformation, the geometry and style of deformation in accretionary wedges is sensitive to shortening velocity. In this study we have constructed a series of analogue models with various shortening velocities in order to study the influence of shortening velocity on the geometry and kinematics of accretionary wedges. Model results illustrate how shortening velocity has an important influence on the geometry and kinematics of the resulting wedge. In general, for models having similar bulk shortening, the accretionary wedges with higher velocities of shortening are roughly steeper, higher and longer, as well as having larger critical wedge angles and height. It accommodates a number of foreland-vergent thrusts, larger fault spacing and displacement rates than those of low- to medium-velocity shortening, which indicates a weak velocity-dependence in geometry of the wedge. Moreover, models with a high velocity of shortening undergo larger amounts of volumetric strain and total layer-parallel shortening than models with low- to medium-velocity shortening. The former accommodate a greater development of back thrusts and asymmetric structures; a backwards-to-forwards style of wedge growth therefore occurs in the frontal zone under high-velocity shortening.

scholarly journals Mapping and classifying large deformation from digital imagery: application to analogue models of lithosphere deformation

2021 ◽  
Author(s):  
Taco Broerse ◽  
Nemanja Krstekanić ◽  
Cor Kasbergen ◽  
Ernst Willingshofer
Keyword(s):  
Large Deformation ◽  
Finite Deformation ◽  
Large Strain ◽  
Shear Zones ◽  
Strike Slip ◽  
Strain Measure ◽  
Lithospheric Deformation ◽  
Analogue Models ◽  
Strain Tensors ◽  
Shape Changes

Summary Particle Image Velocimetry (PIV), a method based on image cross-correlation, is widely used for obtaining velocity fields from time series of images of deforming objects. Rather than instantaneous velocities, we are interested in reconstructing cumulative deformation, and use PIV-derived incremental displacements for this purpose. Our focus is on analogue models of tectonic processes, which can accumulate large deformation. Importantly, PIV provides incremental displacements during analogue model evolution in a spatial reference (Eulerian) frame, without the need for explicit markers in a model. We integrate the displacements in a material reference (Lagrangian) frame, such that displacements can be integrated to track the spatial accumulative deformation field as a function of time. To describe cumulative, finite deformation, various strain tensors have been developed, and we discuss what strain measure best describes large shape changes, as standard infinitesimal strain tensors no longer apply for large deformation. PIV or comparable techniques have become a common method to determine strain in analogue models. However, the qualitative interpretation of observed strain has remained problematic for complex settings. Hence, PIV-derived displacements have not been fully exploited before, as methods to qualitatively characterize cumulative, large strain have been lacking. Notably, in tectonic settings, different types of deformation - extension, shortening, strike-slip - can be superimposed. We demonstrate that when shape changes are described in terms of Hencky strains, a logarithmic strain measure, finite deformation can be qualitatively described based on the relative magnitude of the two principal Hencky strains. Thereby, our method introduces a physically meaningful classification of large 2D strains. We show that our strain type classification method allows for accurate mapping of tectonic structures in analogue models of lithospheric deformation, and complements visual inspection of fault geometries. Our method can easily discern complex strike-slip shear zones, thrust faults and extensional structures and its evolution in time. Our newly developed software to compute deformation is freely available and can be used to post-process incremental displacements from PIV or similar autocorrelation methods.

Structural Development and Geomorphic Relationship in Wadi Atyaruh, Al Jabal Al Akhdar, NE Libya

2021 ◽  
Vol 5 (1) ◽  
pp. 12-23
Author(s):  
Fawzi Moftah ◽  
MacTar Mohamed ◽  
Alzubair Abousaif
Keyword(s):  
Drainage Basin ◽  
Drainage System ◽  
Strike Slip ◽  
Geographical Information ◽  
Mature Stage ◽  
Groundwater Prospect ◽  
Structural Development ◽  
Drainage Pattern ◽  
Principal Stresses ◽  
Gis And Remote Sensing

The present study has been carried out to analyze the relationship between faulting and geomorphology of the Wadi Atyaruh to reveal the effect of structures on the morphology and distribution of the different karst features. Geographical Information System (GIS) and Remote Sensing (RS) techniques were applied to investigate morphological and topographic characteristics of Wadi Atyaruh, based on ASTER Global Digital Elevation Model (ASTER GDEM) Version 3 (V3) data. Dextral strike-slip fault is the main faulting type in the valley. Conjugate faults system has been found in the study area, which reveals the orientations of the principal stresses. Wadi Atyaruh consists mainly of Dernah formations (Eocene) and Quaternary deposits. Two types of Karren have been recognized, they are Rillen karren and solution basis which are well distributed in Darnah formation. Caves are found in the Darnah formation, the passages and chambers of these caves show a phreatic bedding plane, elliptical shape, laminar profiles, and rectangular and rounded top vadose profiles. The drainage system of this valley is sub-parallel drainage pattern to dendritic drainage pattern, indicating that the area has affected by strike-slip movement (Dextral), joints and it has steep slopes. interpretation of DEM of study area indicate moderate and high relief, low run off and high infiltrations due to the nature of the fracture carbonate rock, the basin have early mature stage of erosion development. Geomorphic parameters such as hill shade, slop, aspect, area shaded and elevation maps, was produced to describe geomorphic forms and processes of the Wadi Atyaruh. The complete morphometric analysis of drainage basin indicates that the given area is having good groundwater prospect.

Structural initiation along the frontal fold-thrust system in the western Indo-Burman Range: Implications for the tectonostratigraphic evolution of the Hatia Trough (Bengal Basin)

2021 ◽  
pp. 1-25
Author(s):  
Rashed Abdullah ◽  
Md. Shahadat Hossain ◽  
Md. Soyeb Aktar ◽  
Md. Soyeb Aktar ◽  
Mohammad Moinul Hossain ◽  
...  
Keyword(s):  
Structural Complexity ◽  
Strike Slip ◽  
Indian Plate ◽  
Bengal Basin ◽  
Structural Development ◽  
Fold Belt ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Thrust System ◽  
Subduction System

The Bengal Basin accommodates an extremely thick Cenozoic sedimentary succession that derived from the uplifted Himalayan and Indo-Burman Orogenic Belts in response to the subduction of the Indian Plate beneath the Eurasian and Burmese plates. The Hatia Trough is a proven petroleum province that occupies much of the southern Bengal Basin. However, the style of deformation, kinematics, and possible timing of structural initiation in the Hatia Trough and the relationship of this deformation to the frontal fold-thrust system in the outer wedge (namely, the Chittagong Tripura Fold Belt) of the Indo-Burman subduction system to the east are largely unknown. Therefore, we carried out a structural interpretation across the eastern Hatia Trough and western Chittagong Tripura Fold Belt based on 2D seismic reflection data. Our result suggests that the syn-kinematic packages correspond to the Pliocene Tipam Group and Pleistocene Dupitila Formation. This implies that the structural development in the western Chittagong Tripura Fold Belt took place from the Pliocene. In the Hatia Trough, the timing of structural activation is slightly later (since the Plio-Pleistocene). In general, fold intensity and structural complexity gradually increase towards the east. The presence of reverse faults with minor strike-slip motion along the frontal thrust system in the outer wedge is also consistent with the regional transpressional structures of the Indo-Burman subduction system. However, to the west, there is no evidence for strike-slip deformation in the Hatia Trough. The restored sections show that the amount of E-W shortening in the Hatia Trough is very low (maximum 1.2%). In contrast, to the east, the amount of shortening is high (maximum 13.5%) in the western margin of the Chittagong Tripura Fold Belt. In both the areas, the key trapping mechanism includes anticlinal traps, although, stratigraphic and combinational traps are possible, but it requires further evaluation.

An Assessment of Earthquake Scaling Relationships for Crustal Earthquakes in Indonesia

2021 ◽  
Author(s):  
Endra Gunawan
Keyword(s):  
Seismic Hazard ◽  
Active Faults ◽  
Hazard Model ◽  
Strike Slip ◽  
Coseismic Deformation ◽  
Maximum Magnitude ◽  
Scaling Relationships ◽  
Rupture Length ◽  
Scaling Relationship ◽  
Earthquake Scaling

Abstract To estimate the hazard posed by active faults, estimates of the maximum magnitude earthquake that could occur on the fault are needed. I compare previously published scaling relationships between earthquake magnitude and rupture length with data from recent earthquakes in Indonesia. I compile a total amount of 13 literatures on investigating coseismic deformation in Indonesia, which then divided into strike-slip and dip-slip earthquake cases. I demonstrate that a different scaling relationship generates different misfit compared to data. For a practical practice of making seismic hazard model in Indonesia, this research shows the suggested reference for a scaling relationship of strike-slip and dip-slip faulting regime. On a practical approach in constructing a logic tree for seismic hazard model, using different weighting between each published earthquake scaling relationship is recommended.

scholarly journals Estimation of EOP from VLBI: Direct Approach

2000 ◽  
Vol 180 ◽  
pp. 254-258 ◽  
Author(s):  
L. Petrov
Keyword(s):  
Time Series ◽  
Harmonic Component ◽  
Segment Length ◽  
Physical Parameters ◽  
Earth Orientation Parameters ◽  
Earth Orientation ◽  
Alternative Approach ◽  
Two Stages ◽  
Orientation Parameters ◽  
Raw Earth

AbstractThe currently adopted strategy of EOP estimation from VLBI is to estimate six parameters: UT1, UT1 rate, pole positions and nutation offsets for each 24-hour session independently. Then the resulting time series of raw Earth orientation parameters are filtered and a regression analysis is performed in order to obtain nutation coefficients, polhode of the pole and other physical parameters. Thus, the latter parameters are obtained indirectly in two stages. An alternative approach of direct estimation of the final Earth orientation parameters is presented. Pole coordinates and UT1 are considered as a sum of three components: the low-period component which is modeled by a cubic spline, the harmonic component which includes forced nutation, precession and sub-daily variations of EOP, and the stochastic component which is modeled by a linear spline with segment length 1-2 hours. All parameters are obtained in a single LSQ solution using all available data.

scholarly journals A DYNAMICAL SYMMETRY OF THE QUASI-SPHERICAL (OR SPHERICAL) COLLAPSE

2005 ◽  
Vol 14 (10) ◽  
pp. 1761-1767 ◽  
Author(s):  
UJJAL DEBNATH ◽  
SUBENOY CHAKRABORTY ◽  
NARESH DADHICH
Keyword(s):  
Kinetic Energy ◽  
Initial Data ◽  
Dynamical Symmetry ◽  
Matter Field ◽  
Physical Parameters ◽  
Data Sets ◽  
Type I ◽  
Data Set ◽  
Spherical Collapse ◽  
Scaling Relationship

By linearly scaling the initial data set (mass and kinetic energy functions), it is found that the dynamics of quasi-spherical (or spherical) collapse remains invariant for dust or a general (Type I) matter field, provided the comoving radius is also appropriately scaled. This defines a symmetry of the quasi spherical (or spherical) collapse. That is, the linear transformation identifies an equivalence class of data sets which lead to the same end result as well as its evolution all through. In particular, it is shown that the physical parameters, density and shear remain invariant. What the transformation is exhibiting is an interesting scaling relationship between mass, kinetic energy and the size of the collapsing sphere which is respected not only by the initial data set but remarkably also by the dynamics of collapse.

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