Surface strong motion associated with a stick-slip event in a foam rubber model of earthquakes

1975 ◽  
Vol 65 (5) ◽  
pp. 1059-1071
Author(s):  
Ralph J. Archuleta ◽  
James N. Brune
Keyword(s):  
Strong Motion ◽  
Laboratory Model ◽  
Transverse Displacement ◽  
Stick Slip ◽  
Shear Wave Speed ◽  
Foam Rubber ◽  
Numerical Predictions ◽  
Rubber Model ◽  
Slip Event ◽  
Parkfield Earthquake

Abstract In this paper, we present and interpret dynamic displacement data for a stick-slip event in a foam rubber model of earthquake faulting. Static displacement data are used to infer the stress drop of about 0.016 μ, where μ is the shear modulus. The rupture velocity 0.7 β, where β is the shear-wave speed, is also inferred from the data. The observed particle displacement and particle velocity data are compared with analytical and numerical predictions. Doppler focusing of energy by rupture propagation is clearly observed. No large transverse displacement pulse such as that observed at Station 2 of the Parkfield earthquake is observed. In addition to its value for testing analytical and numerical predictions, the laboratory model provides much needed information on the distribution of strong ground motion in the neighborhood of a fault and thus helps in the problem of microzonation for earthquakes.

Earthquake modeling by stick-slip along precut surfaces in stressed foam rubber

1973 ◽  
Vol 63 (6-1) ◽  
pp. 2105-2119
Author(s):  
James N. Brune
Keyword(s):  
Low Frequency ◽  
Strong Motion ◽  
Rupture Propagation ◽  
Fault Creep ◽  
Stick Slip ◽  
Multiple Events ◽  
Underground Nuclear Explosions ◽  
Foam Rubber ◽  
Particle Velocities ◽  
Stress Drops

Abstract Stick-slip along precut surfaces in stressed foam rubber is similar to earthquake faulting, stick-slip in rock specimens, and theoretical predictions. An additional feature is the common occurrence of multiple events. A significant amount of slip occurs as fault creep. For simple one-slip events on a long fault, the peak particle velocities near the center of the fault average about half the value Δσβ/μ, with Δσβ/μ apparently being a good upper bound. The variation is probably due to focusing by rupture propagation. On a circular fault, the peak values average 3 to 4 times less, partly a result of a greater amount of fault creep, and probably, partly a result of focusing by rupture propagation. Total stress drops are typically about 10 to 20 per cent of the absolute stress, and during individual events about 80 to 90 per cent of the released strain energy is dissipated as friction. For multiple events the cumulative source time function is usually much longer than the source dimension divided by the shear-wave velocity. Thus, the far-field spectrum would have the shape for fractional stress drop, but the low-frequency spectral corner would not correspond to the fault dimension; thus, the inferred stress drops would be too low. Multiple events may explain some anomalously low inferred stress drops for small earthquakes and may partly explain the success of surface-wave excitation as a method of distinguishing underground nuclear explosions from earthquakes. Foam rubber models may be used to study strong motion around various types of faults and, thus, aid in the problem of microzonation.

Elastic displacements in the near-field of a propagating fault

1969 ◽  
Vol 59 (2) ◽  
pp. 865-908
Author(s):  
N. A. Haskell
Keyword(s):  
Fault Plane ◽  
Near Field ◽  
Strong Motion ◽  
Dislocation Motion ◽  
Displacement Discontinuity ◽  
Wave Form ◽  
Strong Motion Station ◽  
Ramp Function ◽  
Wave Forms ◽  
Parkfield Earthquake

abstract Displacement, particle velocity, and acceleration wave forms in the near field of a propagating fault have been computed by numerical integration of the Green's function integrals for an infinite medium. The displacement discontinuity (dislocation) on the fault plane is assumed to have the form of a unilaterally propagating finite ramp function in time. The calculated wave forms in the vicinity of the fault plane are quite similar to those observed at the strong motion station nearest the fault plane at the Parkfield earthquake. The comparison suggests that the propagating ramp time function is roughly representative of the main features of the dislocation motion on the fault plane, but that the actual motion has somewhat more high frequency complexity. Calculated amplitudes indicate that the average final dislocation on the fault at the Parkfield earthquake was more than an order of magnitude greater than the offsets observed on the visible surface trace. Computer generated wave form plots are presented for a variety of locations with respect to the fault plane and for two different assumptions on the relation between fault length and ramp function duration.

Control of rupture by fault geometry during the 1966 parkfield earthquake

1981 ◽  
Vol 71 (1) ◽  
pp. 95-116 ◽  
Author(s):  
Allan G. Lindh ◽  
David M. Boore
Keyword(s):  
Main Shock ◽  
Fault Plane ◽  
San Andreas Fault ◽  
Strong Motion ◽  
P Wave ◽  
Fault Geometry ◽  
Dynamic Rupture ◽  
San Andreas ◽  
Hill Station ◽  
Parkfield Earthquake

abstract A reanalysis of the available data for the 1966 Parkfield, California, earthquake (ML=512) suggests that although the ground breakage and aftershocks extended about 40 km along the San Andreas Fault, the initial dynamic rupture was only 20 to 25 km in length. The foreshocks and the point of initiation of the main event locate at a small bend in the mapped trace of the fault. Detailed analysis of the P-wave first motions from these events at the Gold Hill station, 20 km southeast, indicates that the bend in the fault extends to depth and apparently represents a physical discontinuity on the fault plane. Other evidence suggests that this discontinuity plays an important part in the recurrence of similar magnitude 5 to 6 earthquakes at Parkfield. Analysis of the strong-motion records suggests that the rupture stopped at another discontinuity in the fault plane, an en-echelon offset near Gold Hill that lies at the boundary on the San Andreas Fault between the zone of aseismic slip and the locked zone on which the great 1857 earthquake occurred. Foreshocks to the 1857 earthquake occurred in this area (Sieh, 1978), and the epicenter of the main shock may have coincided with the offset zone. If it did, a detailed study of the geological and geophysical character of the region might be rewarding in terms of understanding how and why great earthquakes initiate where they do.

Approximate method to estimate the short-period strong motion spectra on bedrock

1981 ◽  
Vol 71 (2) ◽  
pp. 491-505
Author(s):  
Katsuhiko Ishida
Keyword(s):  
Earthquake Swarm ◽  
Strong Motion ◽  
Fourier Amplitude ◽  
Period Range ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Short Period ◽  
Amplitude Spectra ◽  
Low Pass ◽  
Parkfield Earthquake

abstract The methodology to estimate the strong motion Fourier amplitude spectra in a short-period range (T ≦ 1 to 2 sec) on a bedrock level is discussed in this paper. The basic idea is that the synthetic strong motion Fourier spectrum F˜A(ω) calculated from smoothed rupture velocity model (Savage, 1972) is approximately similar to that of low-pass-filtered strong earthquake ground motion at a site in a period range T ≧ 1 to 2 sec: F˜A(ω)=B˜(ω)·A(ω). B˜(ω) is an observed Fourier spectrum on a bedrock level and A(ω) is a low-pass filter. As a low-pass filter, the following relation, A ( T ) = · a · T n a T n + 1 , ( T = 2 π / ω ) , is assumed. In order to estimate the characteristic coefficients {n} and {a}, the Tokachi-Oki earthquake (1968), the Parkfield earthquake (1966), and the Matsushiro earthquake swarm (1966) were analyzed. The results obtained indicate that: (1) the coefficient {n} is nearly two for three earthquakes, and {a} is nearly one for the Tokachi-Oki earthquake, eight for the Parkfield earthquake, and four for the Matsushiro earthquake swarm, respectively; (2) the coefficient {a} is related with stress drop Δσ as (a = 0.07.Δσ). Using this relationship between {a} and Δσ, the coefficients {a} of past large earthquakes were estimated. The Fourier amplitude spectra on a bedrock level are also estimated using an inverse filtering method of A ( T ) = a T 2 a T 2 + 1 .

Waveform modeling of the November 1987 Superstition Hills earthquakes

1989 ◽  
Vol 79 (2) ◽  
pp. 500-514 ◽  
Author(s):  
Allison L. Bent ◽  
Donald V. Helmberger ◽  
Richard J. Stead ◽  
Phyllis Ho-Liu
Keyword(s):  
Body Wave ◽  
Source Parameters ◽  
Strong Motion ◽  
Source Depth ◽  
Strong Motion Data ◽  
Waveform Modeling ◽  
Motion Data ◽  
Teleseismic Data ◽  
Slip Event ◽  
Double Event

Abstract Long-period body-wave data recorded at teleseismic distances and strong-motion data at Pasadena for the Superstition Hills earthquakes of 24 November 1987 are modeled to obtain the source parameters. We will refer to the event that occurred at 0153 UT as EQ1 and the event at 1316 UT as EQ2. At all distances the first earthquake appears to be a simple left-lateral strike-slip event on a fault striking NE. It is a relatively deep event with a source depth of 10 km. It has a teleseismic moment of 2.7 ×1025 dyne cm. The second and more complex event was modeled in two ways: by using EQ1 as the Green's function and by using a more traditional forward modeling technique to create synthetic seismograms. The first method indicated that EQ2 was a double event with both subevents similar, but not identical to EQ1 and separated by about 7.5 sec. From the synthetic seismogram study we obtained a strike of 305° for the first subevent and 320° for the second. Both have dips of 80° and rakes of 175°. The first subevent has a moment of 3.6 ×1025 which is half that of the second. We obtain depths of at least 6 km. The teleseismic data indicate a preferred subevent separation of 30 km with the second almost due south of the first, but the error bounds are substantial. This would suggest that the subevents occurred on conjugate faults. The strong-motion data at PAS, however, imply a much smaller source separation, with the sources probably produced by asperities.

Influence of the Structure of a Gouge-Filled Fault on the Parameters of Acoustic Emission

2019 ◽  
Vol 105 (5) ◽  
pp. 759-765 ◽  
Author(s):  
Alexey A. Ostapchuk ◽  
Kseniya G. Morozova ◽  
Dmitry V. Pavlov
Keyword(s):  
Acoustic Emission ◽  
Laboratory Experiments ◽  
Shear Crack ◽  
Kinematic Parameters ◽  
Stick Slip ◽  
Omori Law ◽  
Shear Loads ◽  
Initial Stage ◽  
Slip Event ◽  
Model Setup

Presented are the results of laboratory experiments on investigating manifestations of acoustic emission (AE) of a gouge-filled fault during stick-slip. The laboratory experiments were held at the slider-model setup, when a granite block slides along a rough granite base under normal and shear loads. In the course of experiments we altered the structure of the two-component filler of the fault and focused on variations of the AE parameters. The kinematic parameters of fault slip events in all the realizations remained approximately the same. The eff ect of gouge structure on the statistics of AE has been revealed. An alteration of proportion of quartz sand / glass beads in the filler of the fault was accompanied by an alteration of the b-value of frequency-energy distribution from 0.53 to 0.85, and the p-value of Omori law from 1.00 to 2.06. Also, it has been demonstrated that the nucleation of a slip event is accompanied by an alteration of the mechanism of AE generation – at the initial stage the 'tensile crack' signals prevailed, while at the final stage – the 'shear crack' signals did. The alteration of AE genesis manifested vividly in a corresponding alteration of the emitted waveforms for all the realizations.

Dynamic Analysis of Dry Frictional Disc Brake System Based on the Rigid-Flexible Coupled Model

2015 ◽  
Vol 07 (03) ◽  
pp. 1550044 ◽  
Author(s):  
Yini Zhao ◽  
Qian Ding
Keyword(s):  
Critical Speed ◽  
Plate Theory ◽  
Coupled Model ◽  
Exponential Model ◽  
Brake System ◽  
Disc Brake ◽  
Transverse Displacement ◽  
Stick Slip ◽  
Coupling Case ◽  
Frictional Disc

A rigid-flexible coupled dynamic model is established to investigate the dynamic behaviors of a disc brake system. The analytical model of the pad includes transverse and circumferential displacements. The disc is modeled using the thin plate theory. A governing equation of the motion of the disc is established. Then the first-order vibration equation is obtained using Galerkin method, considering only the transverse displacement. The friction between the pad and disk among the contacting area is estimated using an exponential model, in which the Stribeck effect is included. Numerical method is applied to reveal the influences of coupling dynamical relationships between the pad and disc on the whole system. The results show that with the variation of disc annular speed, the pad keeps vibrating with small amplitude due to the sustaining variation of the contacting pressure and friction. Stick-slip flutter happens as the velocity is lower than a critical speed and strong movement coupling between elements of the system brings earlier occurrence of the frictional flutter. Besides, for strong movement coupling case, before the critical speed, there are intermittent frequency ranges among which the amplitude is quite higher, which is due to a redistribution of friction and contacting pressure.

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