Influence of undulating fault surface properties on its seismic waves during fault-slip

2015 ◽  
Vol 30 (1) ◽  
pp. 1-12 ◽  
Author(s):  
A. Sainoki ◽  
H.S. Mitri
Keyword(s):  
Surface Properties ◽  
Seismic Waves ◽  
Fault Slip ◽  
Fault Surface

A critical look at the Wallace-Bott hypothesis in fault-slip analysis

2013 ◽  
Vol 184 (4-5) ◽  
pp. 299-306 ◽  
Author(s):  
Richard J. Lisle
Keyword(s):  
Shear Stress ◽  
Maximum Shear Stress ◽  
Fault Slip ◽  
Shear Stresses ◽  
Homogeneous State ◽  
Slip Direction ◽  
Fault Surface ◽  
State Of Stress ◽  
Simultaneous Movement

AbstractThe assumption is widely made that slip on faults occurs in the direction of maximum resolved shear stress, an assumption known as the Wallace-Bott hypothesis. This assumption is used to theoretically predict slip directions from known in situ stresses, and also as the basis of palaeostress inversion from fault-slip data. This paper examines different situations in relation to the appropriateness of this assumption. Firstly, it is shown that the magnitude of the shear stress resolved within a plane is a function with a poorly defined maximum direction, so that shear stress values greater than 90% of the maximum occur within a wide angular range (± 26°) degrees. The situation of simultaneous movement on pairs of faults requires slip on each fault to be parallel to their mutual line of intersection. However, the resolved shear stresses arising from a homogeneous state of stress do not accord with such a slip arrangement except in the case of pairs of perpendicular faults. Where fault surfaces are non-planar, the directions of resolved shear stress in general give, according to the Wallace-Bott hypothesis, a set of slip directions of rigid fault blocks, which is generally kinematically incompatible. Finally, a simple model of a corrugated fault suggests that any anisotropy of the shear strength of the fault such as that arising from fault surface topography, can lead to a significant angular difference between the directions of maximum shear stress and the slip direction.These findings have relevance to the design of procedures used to estimate palaeostresses and the amount of data required for this type of analysis.

Direct observation of rupture propagation during the 1979 Imperial Valley earthquake using a short baseline accelerometer array

1984 ◽  
Vol 74 (6) ◽  
pp. 2083-2114
Author(s):  
Paul Spudich ◽  
Edward Cranswick
Keyword(s):  
Seismic Waves ◽  
Main Shock ◽  
Ground Motions ◽  
P Wave ◽  
Time Base ◽  
Correlation Technique ◽  
Imperial Valley ◽  
Short Baseline ◽  
Fault Surface ◽  
S Waves

Abstract The 1979 Imperial Valley, California, earthquake (Ms = 6.9) was recorded on the El Centro differential array, a 213-m-long linear array of 5 three-component digital accelerometers 5.6 km from the nearest tectonic surface rupture. Although absolute time was not recorded on the array elements, a relative time base was established using the main shock hypocentral P wave and the P and S waves from a later aftershock. A cross-correlation technique was used to measure the difference in arrival times of individual seismic waves in a moving 0.6 to 1.2 sec window at each array element, which would then be converted into the wave's slowness (1/velocity) along the array. When applied to the main shock vertical and horizontal accelerograms, results from both components of motion indicated that the early arriving energy came from a source to the south of the array, and the source of the energy moved rapidly to the north of the array during the strong shaking. The ground motions at the array elements were well correlated for about the first 11 sec of motion. These observations suggest that we have observed the initiation of rupture south of the array and its subsequent propagation along the fault to a position north of the array in about 10 sec, and that the energy was radiated from a fairly compact region around the rupture front. If the observed vertical and horizontal ground motions are assumed to be caused by P and S waves, respectively, then the observed slownesses show irregularities which can be interpreted as implying that the observed high-frequency ground motions originated at irregularly distributed regions on the fault surface, or that the rupture velocity was variable, or both. One possible interpretation of the data suggests that the rupture proceeded at near P-wave velocity over a 7-km-long section of fault. Average rupture velocities of about 2.7 to 3.2 km/sec at 8 km depth are consistent with the data, and 2.8 km/sec is weakly preferred under the assumption that rupture propagates at a fixed fraction of the shear velocity. The large vertical pulse, which had a peak acceleration of 1.7 g at E06, was emitted from the portion of the fault extending 25 to 30 km northwest of the hypocenter near Meloland overpass, and not from the point on the fault closest to the differential array. Nothing can be said about fault behavior southeast of the hypocenter.

scholarly journals A calculation methodology of fault relative displacement used to study the mechanical characteristic of fault slip

2021 ◽  
Vol 18 (6) ◽  
pp. 920-942
Author(s):  
Hongwei Wang ◽  
Ruiming Shi ◽  
Daixin Deng ◽  
Fan Cui ◽  
Yaodong Jiang
Keyword(s):  
Relative Displacement ◽  
Fault Slip ◽  
Mine Safety ◽  
Rock Stratum ◽  
Relative Slip ◽  
Fault Surface ◽  
Calculation Methodology ◽  
Mining Face ◽  
Local Slip ◽  
Seam Mining

Abstract Fault slip caused by mining disturbance is a crucial issue that can pose considerable threats to the mine safety. This paper proposes a point-by-point integration calculated methodology of fault relative slip and studies fault instability behavior induced by coal seam mining. A physical model with the existence of a fault and an extra-thick rock stratum is constructed to simulate the fault movement and calculate relative slip using the methodology. The results indicate that the fault relative slip can be regarded as a dynamic evolution process from local slip to global slip on the fault surface. The movement of surrounding rock masses near the fault experiences three stages, including along vertical downward, parallel to the fault and then approximately perpendicular to the fault. There will be an undamaged zone in the extra-thick rock strata when the mining face is near the fault structure. The collapse and instability of this undamaged zone could induce a violent fault relative slip. In addition, the influence of dip angles on the fault relative slip is also discussed. A formula for risk of fault relative slip is further proposed by fitting the relative displacement curves with different fault dip angles.

3D seismic image processing for faults

Geophysics ◽  
2016 ◽  
Vol 81 (2) ◽  
pp. IM1-IM11 ◽  
Author(s):  
Xinming Wu ◽  
Dave Hale
Keyword(s):  
Image Processing ◽  
Data Structure ◽  
Linked Data ◽  
Difficult Problem ◽  
Fault Slip ◽  
3D Seismic ◽  
Fault Surface ◽  
Subsequent Processing ◽  
Seismic Image ◽  
Seismic Images

Numerous methods have been proposed to automatically extract fault surfaces from 3D seismic images, and those surfaces are often represented by meshes of triangles or quadrilaterals. However, extraction of intersecting faults is still a difficult problem that is not well addressed. Moreover, mesh data structures are more complex than the arrays used to represent seismic images, and they are more complex than necessary for subsequent processing tasks, such as that of automatically estimating fault slip vectors. We have represented a fault surface using a simpler linked data structure, in which each sample of a fault corresponded to exactly one seismic image sample, and the fault samples were linked above and below in the fault dip directions, and left and right in the fault strike directions. This linked data structure was easy to exchange between computers and facilitated subsequent image processing for faults. We then developed a method to construct complete fault surfaces without holes using this simple data structure and to extract multiple intersecting fault surfaces from 3D seismic images. Finally, we used the same structure in subsequent processing to estimate fault slip vectors and to assess the accuracy of estimated slips by unfaulting the seismic images.

Laboratory study on the effects of fault waviness on granodiorite stick-slip instabilities

2020 ◽  
Vol 221 (2) ◽  
pp. 1281-1291
Author(s):  
Yan-Qun Zhuo ◽  
Yanshuang Guo ◽  
Shunyun Chen ◽  
Yuntao Ji
Keyword(s):  
Laboratory Study ◽  
Contact Area ◽  
Surface Profile ◽  
Fault Slip ◽  
Stick Slip ◽  
Fault Surface ◽  
State Dependent ◽  
Gradual Evolution ◽  
Large Contact Area ◽  
Contact Distribution

SUMMARY The effects of fault waviness on the fault slip modes are unclear. Laboratory study on the effects of the centimetre-scale fault contact distribution, which is mainly controlled by the fault waviness, on granodiorite stick-slip instabilities may help to unveil some aspects of the problem. The fast and slow stick-slip motions were separately generated in two granodiorite samples of the same roughness but different fault contact distributions in the centimetre scale in the laboratory. The experimental results show the following: (1) the fault with the small contact area and heterogeneous contact distribution generates fast stick-slip instabilities, while the fault with the large contact area and homogeneous contact distribution produces slow stick-slip events; (2) the nucleation processes of the fast stick-slip events are characterized by abrupt changes once the nucleation zones expand to the critical nucleation length that is observed to be shorter than the fault length, while the slow stick-slip events appear as a gradual evolution of the nucleation zones leading to total fault sliding. These indicate that, unlike the micron-scale fault contact distribution controlled by roughness, which depends mainly on the grain size of the abrasives used for lapping the fault surface, the centimetre-scale fault contact distribution, which depends mainly on the waviness of the fault surface profile, also plays an important role in the fault slip modes. In addition, the effects of the fault waviness on the fault friction properties are preliminarily analysed based on the rate- and state-dependent friction law.

scholarly journals Calculation of the local rupture speed of dynamically propagating earthquakes

2014 ◽  
Vol 56 (5) ◽  
Author(s):  
Andrea Bizzarri
Keyword(s):  
Slip Velocity ◽  
Ground Motions ◽  
Maximum Yield ◽  
Fault Slip ◽  
Order Of Accuracy ◽  
Fault Surface ◽  
Threshold Criterion ◽  
Rupture Speed ◽  
Special Case

The velocity at which a propagating earthquake advances on the fault surface is of pivotal importance in the contest of the source dynamics and in the modeling of the ground motions generation. In this paper the problem of the determination of the rupture speed (<em>v_<sub>r</sub></em>) is considered. The comparison of different numerical schemes to compute <em>v<sub>r</sub></em> from the rupture time (<em>t_<sub>r</sub></em>) shows that, in general, central finite differences schemes are more accurate than forward or backward schemes, regardless the order of accuracy. Overall, the most efficient and accurate algorithm is the five–points stencil method at the second–order of accuracy. It is also shown how the determination of <em>t_<sub>r</sub></em> can affect <em>v<sub>_r </sub></em>; numerical results indicate that if the fault slip velocity threshold (<em>v_<sub>l</sub></em>) used to define <em>t_<sub>r</sub></em> is too high (<em>v<sub>_l</sub></em> ≥ 0.1 m/s) the details of the rupture are missed, for instance the rupture tip bifurcation occurring for 2–D supershear rupture. On the other hand, for <em>v_<sub>l</sub></em> ≤ 0.01 m/s the results appear to be stable and independent on the choice of <em>v_<sub>l </sub></em>. Finally, it is demonstrated that in the special case of the linear slip–weakening friction law the definitions of <em>t_<sub>r</sub></em> from the threshold criterion on the fault slip velocity and from the achievement of the maximum yield stress are practically equivalent.

Simultaneous Bayesian Estimation of Complex Non-planar Earthquake Fault Geometry and Spatially-variable Slip from Geodetic Data

2020 ◽  
Author(s):  
Rishabh Dutta ◽  
Sigurjón Jónsson ◽  
Hannes Vasyura-Bathke
Keyword(s):  
Bayesian Estimation ◽  
Surface Deformation ◽  
Spatial Scales ◽  
Model Space ◽  
Fault Slip ◽  
Geodetic Data ◽  
Fault Geometry ◽  
Earthquake Fault ◽  
Fault Surface ◽  
Planar Fault

&lt;p&gt;Earthquake fault ruptures are typically complex and can consist of en echelon segments, have bends, large step-overs, and be curved or warped at different spatial scales. Although surface fault ruptures can be mapped using a variety of geological and geophysical techniques, the subsurface topology of faults is challenging to estimate. One of the main options is to use geodetic data (InSAR and GPS) of coseismic surface deformation to estimate the subsurface earthquake fault geometry along with the distributed slip. The general practice is to assume a planar fault surface and estimate the strike and dip of a simple rectangular fault prior to the spatially-variable slip estimation. Using such simplistic fault geometry during source fault estimations of large earthquakes rarely captures all the crustal deformation details seen in the data and can cause biased estimation results of the fault slip. Here, we show how complex non-planar fault geometry can be estimated simultaneously with spatially-variable slip from geodetic data in a Bayesian framework, where our non-planar fault geometry parametrization approach allows for various undulations of the fault surface in both the along-strike and down-dip directions.&lt;/p&gt;&lt;p&gt;We exemplify this approach through synthetic tests considering a checkerboard-like slip pattern on a listric non-planar fault. The results show that fault slip can be over-estimated by about 50-100% when using pre-assumed planar fault geometry. In contrast, both the non-planar fault geometry and spatially-variable slip are better retrieved when using our estimation approach. We then apply this modeling approach to the 2011 M&lt;sub&gt;W&lt;/sub&gt;9.1 megathrust Tohoku-Oki (Japan) earthquake. Here we use prior information like the location of the trench and earthquake hypocenters during the Bayesian estimation to reduce the extent of the model space. The resulting fault geometry shows variations in fault dip in both the along-strike and down-dip directions that compare well with Hayes&amp;#8217; slab1.0 model of the subduction interface. The estimated fault slip is also comparable to the results that pre-defined the fault geometry using the slab1.0 model. In the future, the proposed method could lead to more realistic source models of major earthquakes, aided by improving computational resources and spatial resolution of geodetic data.&lt;/p&gt;

Sharp geodetic fault slip models for an improved understanding of volcano flank dynamics

2020 ◽  
Author(s):  
Pablo Gonzalez
Keyword(s):  
Dynamic Models ◽  
Shear Zones ◽  
Kilauea Volcano ◽  
Fault Slip ◽  
Physical Processes ◽  
Sector Collapse ◽  
Fault Surface ◽  
Kīlauea Volcano ◽  
The Stability ◽  
Southern Flank

&lt;p&gt;The study of the stability of volcano flanks has been an active topic of research for the last few decades. In 2018, two major events renewed attention in this hazardous processes. In May 2018, following the beginning of a flank eruption at Kilauea volcano in Hawai&amp;#8217;i, a M6.9 earthquake occurred along the Southern flank of Kilauea marking a dramatic but transient acceleration from its secular deformation rate. Alternatively, in December 2018, an intense period of volcanic activity preceded a catastrophic sector collapse which triggered a devastating tsunami at Anak Krakatou volcano (Indonesia). The two contrasting behavior events reveal our poor understanding of the physical processes controlling volcano stability.&lt;/p&gt;&lt;p&gt;Ultimately, instability of volcano flanks is characterized by the development and evolution of failure surfaces (faults and/or basal shear zones). Once established, for example at a rheological interface, a decollement fault should be a key element in the control of the mechanical interplay between the volcano-tectonic and gravitational forces. In this communication, I review our ability to map surface displacements measured with geodetic techniques into frictionally distinct regions on the fault surface. I explore a range of inverse modeling methods to estimate bounds on the extend of geodetically constrained fault slip areas. I apply the methods to the Southern flank of Kilauea volcano. The range of different solutions for fault slip models allows to critically assess whether there are regions of stable or variable frictional conditions. Mapping accurately the frictional behavior and constraining its location region will allow to generate more realistic dynamic models of volcano flanks and improve our understanding the physical processes controlling volcano stability.&lt;/p&gt;

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