scholarly journals Analytical representation of the fault slip velocity from spontaneous dynamic earthquake models

2012 ◽  
Vol 117 (B6) ◽  
pp. n/a-n/a ◽  
Author(s):  
Andrea Bizzarri
Keyword(s):  
Slip Velocity ◽  
Fault Slip ◽  
Analytical Representation ◽  
Earthquake Models

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.

Dilation and compaction accompanying changes in slip velocity in clay-bearing fault gouges

2021 ◽  
Author(s):  
Isabel Ashman ◽  
Daniel Faulkner
Keyword(s):  
Normal Stress ◽  
Pore Pressure ◽  
Volume Change ◽  
Slip Velocity ◽  
Fault Slip ◽  
Slow Slip ◽  
Volume Changes ◽  
Effective Normal Stress ◽  
Earthquake Nucleation ◽  
Fault Gouges

&lt;p&gt;Many natural fault cores comprise volumes of extremely fine, low permeability, clay-bearing fault rocks. Should these fault rocks undergo transient volume changes in response to changes in fault slip velocity, the subsequent pore pressure transients would produce significant fault weakening or strengthening, strongly affecting earthquake nucleation and possibly leading to episodic slow slip events. Dilatancy at slow slip velocity has previously been measured in quartz-rich gouges but little is known about gouge containing clay. In this work, the mechanical behaviour of synthetic quartz-kaolinite fault gouges and their volume response to velocity step changes were investigated in a suite of triaxial deformation experiments at effective normal stresses of 60MPa, 25MPa and 10MPa. Kaolinite content was varied from 0 to 100wt% and slip velocity was varied between 0.3 and 3 microns/s.&lt;/p&gt;&lt;p&gt;Upon a 10-fold velocity increase or decrease, gouges of all kaolinite-quartz contents displayed measurable volume change transients. The results show the volume change transients are independent of effective normal stress but are sensitive to gouge kaolinite content. Peak dilation values did not occur in the pure quartz gouges, but rather in gouges containing 10wt% to 20wt% kaolinite. Above a kaolinite content of 10wt% to 20wt%, both dilation and compaction decreased with increasing gouge kaolinite content. At 25MPa effective normal stress, the normalised volume changes decreased from 0.1% to 0.06% at 10wt% to 100wt% kaolinite.&amp;#160; The gouge mechanical behaviour shows that increasing the gouge kaolinite content decreases the gouge frictional strength and promotes more stable sliding, rather than earthquake slip. Increasing the effective normal stress slightly decreases the frictional strength, enhances the chance of earthquake nucleation, and has no discernible effect on the magnitude of the pore volume changes during slip velocity changes.&lt;/p&gt;&lt;p&gt;Low permeabilities of clay-rich fault gouges, coupled with the observed volume change transients, could produce pore pressure fluctuations up to 10MPa in response to fault slip. This assumes no fluid escape from an isolated fault core. Where the permeability is finite, any pore pressure changes will be mediated by fluid influx into the gouge. Volume change transients could therefore be a significant factor in determining whether fault slip leads to earthquake nucleation or a dampened response, possibly resulting in episodic slow slip in low permeability fault rock volumes.&lt;/p&gt;

Exploring frictional velocity dependence as a mechanism for slow earthquake rupture

2020 ◽  
Author(s):  
Julia Krogh ◽  
Chris Marone
Keyword(s):  
Slip Velocity ◽  
Fault Slip ◽  
Slow Slip ◽  
Velocity Dependence ◽  
Friction Modeling ◽  
Slow Slip Events ◽  
Slow Earthquake ◽  
Stable Conditions ◽  
Slow Earthquakes ◽  
The Stability

&lt;p&gt;Earthquakes fail through a spectrum of slip modes ranging from slow slip to fast elastodynamic rupture. Slow earthquakes, or slow-slip events, represent fault slip behaviors that involve quasi-dynamic, self-sustained rupture propagation. To better understand the mechanisms that limit the slip speed and propagation rates of slow slip, we focus on a particular parameter: the critical frictional weakening rate of the fault surface, &lt;em&gt;k&lt;sub&gt;c&lt;/sub&gt;&lt;/em&gt;. When &lt;em&gt;k&lt;sub&gt;c&lt;/sub&gt;&lt;/em&gt; is approximately equal to &lt;em&gt;k&lt;/em&gt;, the elastic loading stiffness of the fault, complex fault slip behaviors including slow-slip events are observed. If &lt;em&gt;k&lt;sub&gt;c&lt;/sub&gt;&lt;/em&gt; has a negative dependence on slip velocity, acceleration during the coseismic phase could decrease &lt;em&gt;k&lt;sub&gt;c&lt;/sub&gt;&lt;/em&gt; until it approximates &lt;em&gt;k&lt;/em&gt;, terminating in a slow earthquake. Here, we describe the results of laboratory experiments designed to quantify the dependence of &lt;em&gt;k&lt;sub&gt;c&lt;/sub&gt;&lt;/em&gt; on frictional slip velocity. We conducted double-direct shear experiments in a biaxial shearing apparatus with 3 mm-thick fault zones composed of quartz powder to simulate fault gouge. We focus on step decreases in slip velocity from 300 to 3 m/s that were performed for a range of normal stresses, from 10 to 20 MPa, which we know to be near the stability transition from stable to unstable sliding defined by &lt;em&gt;k/k&lt;sub&gt;c&lt;/sub&gt;&lt;/em&gt; ~ 1.0. Under stable conditions, rate-state friction modeling was used to determine &lt;em&gt;k&lt;sub&gt;c&lt;/sub&gt;&lt;/em&gt; for each velocity step. Our data provide direct insight on the stability transition associated with &lt;em&gt;k&lt;sub&gt;c&lt;/sub&gt;(V)&lt;/em&gt;, including experiments for which slow-slip instabilities grew larger and faster throughout velocity-step sequences. Ultimately, both numerical modeling and observational data indicate that the velocity dependence of &lt;em&gt;k&lt;sub&gt;c&lt;/sub&gt;&lt;/em&gt; is an important parameter when considering the mechanisms of slow earthquake nucleation.&amp;#160;&lt;/p&gt;

Analysis of Rough Porous Inclined Slider Bearing Lubricated With a Ferrofluid Considering Slip Velocity

2019 ◽  
Vol 7 (1) ◽  
pp. 387-396 ◽  
Author(s):  
Mohmmadraiyan M. Munshi ◽  
Ashok R. Patel ◽  
Gunamani Deheri
Keyword(s):  
Slip Velocity ◽  
Slider Bearing

Analytical Representation of the Density Function of Normal Distribution of Noise

2015 ◽  
Vol 47 (8) ◽  
pp. 24-40 ◽  
Author(s):  
Telman Abbas ogly Aliev ◽  
Naila F. Musaeva ◽  
Matanat Tair kyzy Suleymanova ◽  
Bahruz Ismail ogly Gazizade
Keyword(s):  
Normal Distribution ◽  
Density Function ◽  
Analytical Representation

Prediction of Tread Pattern Wear by an Explicit Finite Element Model3

2007 ◽  
Vol 35 (4) ◽  
pp. 276-299 ◽  
Author(s):  
J. C. Cho ◽  
B. C. Jung
Keyword(s):  
Finite Element ◽  
Wear Rate ◽  
Tangential Stress ◽  
Rate Equation ◽  
Constitutive Equations ◽  
Slip Velocity ◽  
Test Results ◽  
Explicit Finite Element ◽  
Driving Condition ◽  
Driving Conditions

Abstract Tread pattern wear is predicted by using an explicit finite element model (FEM) and compared with the indoor drum test results under a set of actual driving conditions. One pattern is used to determine the wear rate equation, which is composed of slip velocity and tangential stress under a single driving condition. Two other patterns with the same size (225/45ZR17) and profile are used to be simulated and compared with the indoor wear test results under the actual driving conditions. As a study on the rubber wear rate equation, trial wear rates are assumed by several constitutive equations and each trial wear rate is integrated along time to yield the total accumulated wear under a selected single cornering condition. The trial constitutive equations are defined by independently varying each exponent of slip velocity and tangential stress. The integrated results are compared with the indoor test results, and the best matching constitutive equation for wear is selected for the following wear simulation of two other patterns under actual driving conditions. Tens of thousands of driving conditions of a tire are categorized into a small number of simplified conditions by a suggested simplification procedure which considers the driving condition frequency and weighting function. Both of these simplified conditions and the original actual conditions are tested on the indoor drum test machines. The two results can be regarded to be in good agreement if the deviation that exists in the data is mainly due to the difference in the test velocity. Therefore, the simplification procedure is justified. By applying the selected wear rate equation and the simplified driving conditions to the explicit FEM simulation, the simulated wear results for the two patterns show good match with the actual indoor wear results.

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