High Frequency Near-Field Ground Motion Excited by Strike-Slip Step Overs

2018 ◽  
Vol 123 (3) ◽  
pp. 2303-2317 ◽  
Author(s):  
Feng Hu ◽  
Jian Wen ◽  
Xiaofei Chen
Keyword(s):  
Ground Motion ◽  
High Frequency ◽  
Near Field ◽  
Strike Slip ◽  
Slip Step

Strain, tilt, and rotation associated with strong ground motion in the vicinity of earthquake faults

1982 ◽  
Vol 72 (5) ◽  
pp. 1717-1738 ◽  
Author(s):  
Michel Bouchon ◽  
Keiiti Aki
Keyword(s):  
Ground Motion ◽  
Rotational Velocity ◽  
Near Field ◽  
Strike Slip ◽  
Phase Velocities ◽  
Crustal Structures ◽  
Time Histories ◽  
San Fernando ◽  
Earthquake Faults ◽  
Strong Ground

abstract In the absence of near-field records of differential ground motion induced by earthquakes, we simulate the time histories of strain, tilt, and rotation in the vicinity of earthquake faults embedded in layered media. We consider the case of both strike-slip and dip-slip fault models and study the effect of different crustal structures. The maximum rotational motion produced by a buried 30-km-long strike-slip fault with slip of 1 m is of the order of 3 × 10−4 rad while the corresponding rotational velocity is about 1.5 × 10−3 rad/sec. A simulation of the San Fernando earthquake yields maximum longitudinal strain and tilt a few kilometers from the fault of the order of 8 × 10−4 and 7 × 10−4 rad. These values being small compared to the amplitude of ground displacement, the results suggest that most of the damage occurring in earthquakes is caused by translation motions. We also show that strain and tilt are closely related to ground velocity and that the phase velocities associated with strong ground motions are controlled by the rupture velocity and the basement rock shearwave velocity.

scholarly journals A physical model of the effect of a shallow weak layer on strong ground motion for strike-slip ruptures

1998 ◽  
Vol 88 (4) ◽  
pp. 1070-1078 ◽  
Author(s):  
James N. Brune ◽  
Abdolrasool Anooshehpoor
Keyword(s):  
Ground Motion ◽  
Rise Time ◽  
High Frequency ◽  
Strong Ground Motion ◽  
Strike Slip ◽  
Weak Zone ◽  
Weak Layer ◽  
Strong Ground ◽  
Frequency Radiation ◽  
Shallow Part

Abstract We report results of foam rubber modeling of the effect of a shallow weak layer on ground motion from strike-slip ruptures. Computer modeling of strong ground motion from strike-slip earthquakes has in some cases involved somewhat arbitrary assumptions about the nature of slip along the shallow part of the fault (e.g., fixing the slip to be zero along the upper 2 km of the fault plane). Fault-slip inversion studies indicate that the high-frequency radiation from the shallow part of strike-slip faults is typically less than that for the deeper parts of the fault. In many cases, faults (1) may be weak along the upper few kilometers of the fault zone and may not be able to maintain high levels of shear strain required for high dynamic energy release during earthquakes and (2) may have different constitutive relations for fault slip, for example, slip strengthening. The object of this article is to present results of physical modeling using a shallow weak layer, in order to support the physical basis for assuming a long rise time and a reduced high-frequency pulse for the slip on the shallow part of faults. A weak zone was modeled by inserting weak plastic layers of a few inches in width into the foam rubber model. The long-term strength of the weak layer is about an order of magnitude less than the rest of the model. The transient strength is velocity strengthening with the strength estimated to be about three times higher at slip velocities typical of dynamic slip events. It appears a 2-km-deep, weak zone along strike-slip faults could indeed reduce the high-frequency energy radiated from shallow slip and that this effect can best be represented by superimposing a small-amplitude, short rise-time pulse at the onset of a much longer rise-time slip. For the 15-cm weak zone, the average pulse amplitude is reduced by a factor of about 0.4. The reduction factor for the 20-cm case is about 0.2. For the 30-cm case, it is about 0.1. From these results, we can see that the thicker the weak layer, the more difficult it is for a short rise-time acceleration pulse to push its way through the weak layer to the surface. The velocity strengthening property of the weak layer further damps the slip motion and increases the rise time. These results support reducing the high-frequency radiation from shallower parts of strike-slip faults in modeling studies if it is known that the shallow part of the fault is weak or has not stored up a large shear stress.

scholarly journals Co-Seismic Ionospheric Disturbance with Alaska Strike-Slip Mw7.9 Earthquake on 23 January 2018 Monitored by GPS

Atmosphere ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 83
Author(s):  
Yongming Zhang ◽  
Xin Liu ◽  
Jinyun Guo ◽  
Kunpeng Shi ◽  
Maosheng Zhou ◽  
...  
Keyword(s):  
Fault Location ◽  
Ionospheric Disturbance ◽  
Near Field ◽  
Singular Spectrum Analysis ◽  
Maximum Amplitude ◽  
Strike Slip ◽  
Ionospheric Disturbances ◽  
Total Electron ◽  
Total Electron Contents ◽  
Alaska Earthquake

The Mw7.9 Alaska earthquake at 09:31:40 UTC on 23 January 2018 occurred as the result of strike slip faulting within the shallow lithosphere of the Pacific plate. Global positioning system (GPS) data were used to calculate the slant total electron contents above the epicenter. The singular spectrum analysis (SSA) method was used to extract detailed ionospheric disturbance information, and to monitor the co-seismic ionospheric disturbances (CIDs) of the Alaska earthquake. The results show that the near-field CIDs were detected 8–12 min after the main shock, and the typical compression-rarefaction wave (N-shaped wave) appeared. The ionospheric disturbances propagate to the southwest at a horizontal velocity of 2.61 km/s within 500 km from the epicenter. The maximum amplitude of CIDs appears about 0.16 TECU (1TECU = 1016 el m−2) near the epicenter, and gradually decreases with the location of sub-ionospheric points (SIPs) far away from the epicenter. The attenuation rate of amplitude slows down as the distance between the SIPs and the epicenter increases. The direction of the CIDs caused by strike-slip faults may be affected by the horizontal direction of fault slip. The propagation characteristics of the ionospheric disturbance in the Alaska earthquake may be related to the complex conditions of focal mechanisms and fault location.

scholarly journals Measurement of high frequency conductivity of oxide-doped anti-ferromagnetic thin film with a near-field scanning microwave microscope

AIP Advances ◽  
2014 ◽  
Vol 4 (4) ◽  
pp. 047114 ◽  
Author(s):  
Z. Wu ◽  
A. D. Souza ◽  
B. Peng ◽  
W. Q. Sun ◽  
S. Y. Xu ◽  
...  
Keyword(s):  
Thin Film ◽  
High Frequency ◽  
Near Field ◽  
Microwave Microscope ◽  
Near Field Scanning

Directivity in NGA Earthquake Ground Motions: Analysis Using Isochrone Theory

2008 ◽  
Vol 24 (1) ◽  
pp. 279-298 ◽  
Author(s):  
Paul Spudich ◽  
Brian S. J. Chiou
Keyword(s):  
Ground Motion ◽  
Ground Motions ◽  
Strike Slip ◽  
Motion Prediction ◽  
Spectral Acceleration ◽  
Correction Factors ◽  
Ground Motion Prediction ◽  
Earthquake Ground Motions

We present correction factors that may be applied to the ground motion prediction relations of Abrahamson and Silva, Boore and Atkinson, Campbell and Bozorgnia, and Chiou and Youngs (all in this volume) to model the azimuthally varying distribution of the GMRotI50 component of ground motion (commonly called “directivity”) around earthquakes. Our correction factors may be used for planar or nonplanar faults having any dip or slip rake (faulting mechanism). Our correction factors predict directivity-induced variations of spectral acceleration that are roughly half of the strike-slip variations predicted by Somerville et. al. (1997), and use of our factors reduces record-to-record sigma by about 2–20% at 5 sec or greater period.

Microearthquake seismicity and tectonics of Coastal Northern California

1970 ◽  
Vol 60 (5) ◽  
pp. 1669-1699 ◽  
Author(s):  
Leonardo Seeber ◽  
Muawia Barazangi ◽  
Ali Nowroozi
Keyword(s):  
High Frequency ◽  
Fault Plane ◽  
San Andreas Fault ◽  
High Gain ◽  
Strike Slip ◽  
Fault System ◽  
Northern California ◽  
Fault Plane Solutions ◽  
Sharp Bend ◽  
San Andreas

Abstract This paper demonstrates that high-gain, high-frequency portable seismographs operated for short intervals can provide unique data on the details of the current tectonic activity in a very small area. Five high-frequency, high-gain seismographs were operated at 25 sites along the coast of northern California during the summer of 1968. Eighty per cent of 160 microearthquakes located in the Cape Mendocino area occurred at depths between 15 and 35 km in a well-defined, horizontal seismic layer. These depths are significantly greater than those reported for other areas along the San Andreas fault system in California. Many of the earthquakes of the Cape Mendocino area occurred in sequences that have approximately the same magnitude versus length of faulting characteristics as other California earthquakes. Consistent first-motion directions are recorded from microearthquakes located within suitably chosen subdivisions of the active area. Composite fault plane solutions indicate that right-lateral movement prevails on strike-slip faults that radiate from Cape Mendocino northwest toward the Gorda basin. This is evidence that the Gorda basin is undergoing internal deformation. Inland, east of Cape Mendocino, a significant component of thrust faulting prevails for all the composite fault plane solutions. Thrusting is predominant in the fault plane solution of the June 26 1968 earthquake located along the Gorda escarpement. In general, the pattern of slip is consistent with a north-south crustal shortening. The Gorda escarpment, the Mattole River Valley, and the 1906 fault break northwest of Shelter Cove define a sharp bend that forms a possible connection between the Mendocino escarpment and the San Andreas fault. The distribution of hypocenters, relative travel times of P waves, and focal mechanisms strongly indicate that the above three features are surface expressions of an important structural boundary. The sharp bend in this boundary, which is concave toward the southwest, would tend to lock the dextral slip along the San Andreas fault and thus cause the regional north-south compression observed at Cape Mendocino. The above conclusions support the hypothesis that dextral strike-slip motion along the San Andreas fault is currently being taken up by slip along the Mendocino escarpment as well as by slip along northwest trending faults in the Gorda basin.

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