Convenient formulas for determining dip-slip fault parameters from geophysical observables

1996 ◽  
Vol 86 (5) ◽  
pp. 1642-1644 ◽  
Author(s):  
Steven C. Cohen
Keyword(s):  
Subduction Zone ◽  
Seismic Parameters ◽  
Fault Parameters ◽  
Dip Angle ◽  
Simple Equations ◽  
Angle Width ◽  
Made In

Abstract Simple equations are presented for estimating slip magnitude, fault dip angle, width of the zone of compression, and other co-seismic parameters from geologic, seismic, and geodetic observations made in subduction zone and continental dip-slip environments. These equations are easy to memorize and use without computational aids.

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. 

scholarly journals Numerical models of slab migration in continental collision zones

Solid Earth ◽  
2012 ◽  
Vol 3 (2) ◽  
pp. 293-306 ◽  
Author(s):  
V. Magni ◽  
J. van Hunen ◽  
F. Funiciello ◽  
C. Faccenna
Keyword(s):  
Subduction Zone ◽  
Plate Tectonics ◽  
Numerical Models ◽  
Continental Collision ◽  
Force Balance ◽  
Small Scale ◽  
Dip Angle ◽  
External Forces ◽  
Stress Dependent ◽  
Subduction System

Abstract. Continental collision is an intrinsic feature of plate tectonics. The closure of an oceanic basin leads to the onset of subduction of buoyant continental material, which slows down and eventually stops the subduction process. In natural cases, evidence of advancing margins has been recognized in continental collision zones such as India-Eurasia and Arabia-Eurasia. We perform a parametric study of the geometrical and rheological influence on subduction dynamics during the subduction of continental lithosphere. In our 2-D numerical models of a free subduction system with temperature and stress-dependent rheology, the trench and the overriding plate move self-consistently as a function of the dynamics of the system (i.e. no external forces are imposed). This setup enables to study how continental subduction influences the trench migration. We found that in all models the slab starts to advance once the continent enters the subduction zone and continues to migrate until few million years after the ultimate slab detachment. Our results support the idea that the advancing mode is favoured and, in part, provided by the intrinsic force balance of continental collision. We suggest that the advance is first induced by the locking of the subduction zone and the subsequent steepening of the slab, and next by the sinking of the deepest oceanic part of the slab, during stretching and break-off of the slab. These processes are responsible for the migration of the subduction zone by triggering small-scale convection cells in the mantle that, in turn, drag the plates. The amount of advance ranges from 40 to 220 km and depends on the dip angle of the slab before the onset of collision.

Fault parameters determined by near- and far-field data: The Wakasa Bay earthquake of March 26, 1963

1974 ◽  
Vol 64 (5) ◽  
pp. 1369-1382 ◽  
Author(s):  
Katsuyuki Abe
Keyword(s):  
Effective Stress ◽  
Stress Drop ◽  
P Wave ◽  
Slip Angle ◽  
Polarization Angle ◽  
S Wave ◽  
Seismological Data ◽  
Fault Parameters ◽  
Wakasa Bay ◽  
Dip Angle

Abstract The source process of the Wakasa Bay earthquake (M = 6.9, 35.80°N, 135.76°E, depth 4 km) which occurred near the west coast of Honshu Island, Japan, on March 26, 1963, is studied on the basis of the seismological data. Dynamic and static parameters of the faulting are determined by directly comparing synthetic seismograms with observed seismograms recorded at seismic near and far distances. The De Hoop-Haskell method is used for the synthesis. The average dislocation is determined to be 60 cm. The overall dislocation velocity is estimated to be 30 cm/sec, the rise time of the slip dislocation being determined as 2 sec. The other fault parameters determined, with supplementary data on the P-wave first motion, the S-wave polarization angle, and the aftershocks, are: source geometry, dip direction N 144°E, dip angle 68°, slip angle 22° (right-lateral strike-slip motion with some dip-slip component); fault dimension, 20 km length by 8 km width; rupture velocity, 2.3 km/sec (bilateral); seismic moment, 3.3 × 1025 dyne-cm; stress drop, 32 bars. The effective stress available to accelerate the fault motion is estimated to be about 40 bars. The approximate agreement between the effective stress and the stress drop suggests that most of the effective stress was released at the time of the earthquake.

scholarly journals Tsunami damage estimation in Esmeraldas, Ecuador using fragility functions

2021 ◽  
Vol 7 (4) ◽  
pp. 669-694
Author(s):  
Teresa Vera San Martín ◽  
◽  
Leonardo Gutierrez ◽  
Mario Palacios ◽  
Erick Mas ◽  
...  
Keyword(s):  
Rake Angle ◽  
Fragility Functions ◽  
Damage Estimation ◽  
Coastal Zones ◽  
National Budget ◽  
Tsunami Damage ◽  
Fault Parameters ◽  
Tsunami Risk ◽  
Source Models ◽  
Dip Angle

<abstract> <p>The current study investigated the probable impact from a tsunami to a populated area located along the northwest ecuadorian coast, specifically in the key oil-industrial city of esmeraldas. a numerical tsunami simulation was performed considering the seismological and tectonic aspects of the area. The damage probability was calculated using fragility functions (ffs). Briefly, 16 cases of source models with slightly different fault parameters were tested, where one was selected as the worst scenario of tsunami inundation. This scenario was a hypothetic earthquake case (mw 8.7) located in front of esmeraldas city, approximately 100 km offshore along the ecuador—colombia trench, with three shallow fault segments (top depth of 10 km), a strike aligned with the trench axis, a middle dip angle of 28°, assuming large slips of 5 to 15 m, and a rake angle of 90°. The results from the numerical simulation were comparable to a similar study previously conducted and with those of historically documented data. The tsunami damage estimation using FFs resulted in estimated damages of 50% and 44% in exposed buildings and population, respectively. Results also showed that the most impacted areas were located next to the coastal shoreline and river. tourism, oil exports, and port activities, in general, would be affected in this scenario; thus, compromising important industries that support the national budget. Results from this study would assist in designing or improving tsunami risk reduction strategies, disaster management, use of coastal zones, and planning better policies.</p> </abstract>

scholarly journals ASSESSMENT OF OPTIMUM VALUE FOR DIP ANGLE AND LOCKING RATE PARAMETERS IN MAKRAN SUBDUCTION ZONE

2017 ◽  
Vol XLII-4/W4 ◽  
pp. 523-529
Author(s):  
A. Safari ◽  
A. M. Abolghasem ◽  
N. Abedini ◽  
Z. Mousavi
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Arabian Plate ◽  
Eurasian Plate ◽  
Makran Subduction Zone ◽  
South Eastern ◽  
Best Value ◽  
Proposed Model ◽  
Sparse Measurements ◽  
Dip Angle

Makran subduction zone is one of the convergent areas that have been studied by spatial geodesy. Makran zone is located in the South Eastern of Iran and South of Pakistan forming the part of Eurasian-Arabian plate's border where oceanic crust in the Arabian plate (or in Oman Sea) subducts under the Eurasian plate ( Farhoudi and Karig, 1977). Due to lack of historical and modern tools in the area, a sampling of sparse measurements of the permanent GPS stations and temporary stations (campaign) has been conducted in the past decade. Makran subduction zone from different perspectives has unusual behaviour: For example, the Eastern and Western parts of the region have very different seismicity and also dip angle of subducted plate is in about 2 to 8 degrees that this value due to the dip angle in other subduction zone is very low. In this study, we want to find the best possible value for parameters that differs Makran subduction zone from other subduction zones. Rigid block modelling method was used to determine these parameters. From the velocity vectors calculated from GPS observations in this area, block model is formed. These observations are obtained from GPS stations that a number of them are located in South Eastern Iran and South Western Pakistan and a station located in North Eastern Oman. According to previous studies in which the locking depth of Makran subduction zone is 38km (Frohling, 2016), in the preparation of this model, parameter value of at least 38 km is considered. With this function, the amount of 2 degree value is the best value for dip angle but for the locking rate there is not any specified amount. Because the proposed model is not sensitive to this parameter. So we can not expect big earthquakes in West of Makran or a low seismicity activity in there but the proposed model definitely shows the Makran subduction layer is locked.

scholarly journals Numerical models of trench migration in continental collision zones

2012 ◽  
Vol 4 (1) ◽  
pp. 429-458 ◽  
Author(s):  
V. Magni ◽  
J. van Hunen ◽  
F. Funiciello ◽  
C. Faccenna
Keyword(s):  
Subduction Zone ◽  
Plate Tectonics ◽  
Numerical Models ◽  
Continental Collision ◽  
Force Balance ◽  
Dip Angle ◽  
External Forces ◽  
Stress Dependent ◽  
Subduction System ◽  
Intrinsic Feature

Abstract. Continental collision is an intrinsic feature of plate tectonics. The closure of an oceanic basin leads to the onset of subduction of buoyant continental material, which slows down and eventually stops the subduction process. We perform a parametric study of the geometrical and rheological influence on subduction dynamics during the subduction of continental lithosphere. In 2-D numerical models of a free subduction system with temperature and stress-dependent rheology, the trench and the overriding plate move self-consistently as a function of the dynamics of the system (i.e. no external forces are imposed). This setup enables to study how continental subduction influences the trench migration. We found that in all models the trench starts to advance once the continent enters the subduction zone and continues to migrate until few million years after the ultimate slab detachment. Our results support the idea that the trench advancing is favoured and, in part provided by, the intrinsic force balance of continental collision. We suggest that the trench advance is first induced by the locking of the subduction zone and the subsequent steepening of the slab, and next by the sinking of the deepest oceanic part of the slab, during stretching and break-off of the slab. The amount of trench advancing ranges from 40 to 220 km and depends on the dip angle of the slab before the onset of collision.

scholarly journals Magnetic anomaly interpretation for a 2D fault-like geologic structures utilizing the global particle swarm method

2021 ◽  
Author(s):  
Khalid S. ESSA ◽  
Yves Géraud ◽  
Alan B. Reid
Keyword(s):  
Magnetic Anomaly ◽  
Goodness Of Fit ◽  
Moving Average ◽  
Particle Swarm ◽  
Theoretical Models ◽  
Shear Zones ◽  
Real Field ◽  
Fault Parameters ◽  
Particle Swarm Method ◽  
Dip Angle

Abstract We establish a method to elucidate the magnetic anomaly due to 2D fault structures, with an evaluation of first moving average residual anomalies utilizing filters of increasing window lengths. After that, the buried fault parameters are estimated using the global particle swarm method. The goodness of fit among the observed and the calculated models is expressed as the root mean squared (RMS) error. The importance of studying and delineating the fault parameters, which include the amplitude factor, the depth to the upper edge, the depth to the lower edge, the fault dip angle, and the position of the origin of the fault, is: (i) solving many problem-related engineering and environmental applications, (ii) describing the accompanying mineralized zones with faults, (iii) describing geological deformation events, (iv) monitoring the subsurface shear zones, (v) defining the environmental effects of the faults before organizing any investments, and (vi) imaging subsurface faults for different scientific studies. Finally, we show the method applied to two theoretical models including the influence of the regional background and the multi-fault effect and to real field examples from Australia and Turkey. Available geologic and geophysical information corroborates our interpretations.

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