Attenuation of High-Frequency P and S Waves in the Crust of Central and Western Tien Shan

2020 ◽  
Vol 177 (9) ◽  
pp. 4127-4142
Author(s):  
Xiaolong Ma ◽  
Zongying Huang
Keyword(s):  
High Frequency ◽  
Tien Shan ◽  
S Waves

Attenuation of High Frequency P and S Waves in the Gujarat Region, India

2010 ◽  
Vol 168 (5) ◽  
pp. 797-813 ◽  
Author(s):  
Sumer Chopra ◽  
Dinesh Kumar ◽  
B. K. Rastogi
Keyword(s):  
High Frequency ◽  
S Waves

Frequency-dependent Attenuation of High-frequency P and S Waves in the Upper Crust in Western Nagano, Japan

1998 ◽  
Vol 153 (2-4) ◽  
pp. 489-502 ◽  
Author(s):  
K. Yoshimoto ◽  
H. Sato ◽  
Y. Iio ◽  
H. Ito ◽  
T. Ohminato ◽  
...  
Keyword(s):  
High Frequency ◽  
Upper Crust ◽  
Frequency Dependent ◽  
S Waves

Spectral Comparison of Vertical and Horizontal Seismic Strong Ground Motions in Alluvial Basins

1998 ◽  
Vol 14 (4) ◽  
pp. 573-595 ◽  
Author(s):  
Rouben V. Amirbekian ◽  
Bruce A. Bolt
Keyword(s):  
High Frequency ◽  
Ground Motions ◽  
Frequency Content ◽  
S Waves ◽  
Anelastic Attenuation ◽  
Similar Distance ◽  
Vertical Ground ◽  
Spectral Comparison ◽  
Wave Conversion ◽  
Strong Ground

We analyze observations from the SMART2 array and the 1994 Northridge, California earthquake of spectral differences between vertical and horizontal strong seismic motions in alluvial basins. Our explanation is that the most energetic of such high-frequency vertical ground accelerations are generated by S-to-P seismic wave conversion within the transition zone between the underlying bedrock and the overlying sedimentary layers. The differences in combined scattering and anelastic attenuation for P and S waves lead to the observed spectral differences of the vertical motions between rock and deep alluvium sites. This model also accounts for the frequency content differences between the vertical and horizontal motions at sites in alluvial basins than at rock sites at similar distance ranges. The high-frequency cutoff of the acceleration power spectrum, fmax, is a useful comparison parameter. The results help in computing matched sets of synthetic ground motions above 2 Hz at alluvial sites.

The Morgan Hill Earthquake of April 24, 1984—The 1.29g Acceleration at Coyote Lake Dam: Due to Directivity, a Double Event, or Both?

1985 ◽  
Vol 1 (3) ◽  
pp. 445-455 ◽  
Author(s):  
Norman A. Abrahamson ◽  
Robert B. Darragh
Keyword(s):  
Spatial Variation ◽  
High Frequency ◽  
Seismic Source ◽  
Fault Rupture ◽  
Constructive Interference ◽  
Ground Acceleration ◽  
Field Station ◽  
S Waves ◽  
Broadband Seismograms ◽  
Double Event

The 1984 Halls Valley (Morgan Hill, California) earthquake had a complex seismic source. Velocities of the major seismic phases measured from continuous broadband seismograms at Berkeley Seismographic Station (BKS) and Richmond Field Station (RFS) show unambiguously that the earthquake is predominantly a double event with the second source hypocenter located approximately 17 km southeast of the mainshock hypocenter given by Bolt, Uhrhammer and Darragh (1985). The southeasterly fault rupture of the first source and the location of the focus of the second source have critical implications for the observed spatial variation of the recorded accelerograms. Of particular engineering interest, the high frequency 1.29g pulse of horizontal ground acceleration measured at Coyote Lake dam can be explained primarily as due to the second source and constructive interference of the principal S waves from the two sources.

High-frequency spectra observed at Anza, California: Implications for Q structure

1988 ◽  
Vol 78 (2) ◽  
pp. 692-707
Author(s):  
S. E. Hough ◽  
J. G. Anderson
Keyword(s):  
High Frequency ◽  
P Waves ◽  
Frequency Spectra ◽  
S Waves ◽  
Intrinsic Attenuation ◽  
Depth Dependence ◽  
Wide Range ◽  
Distance Dependence ◽  
Attenuation Mechanism ◽  
Inversion Procedure

Abstract Data from the Anza array in southern California have been analyzed to yield a model for the depth dependence of attenuation. The result is obtained from a formal inversion of the distance dependence of the spectral decay parameter, κ, observed from sources at a wide range of distances from single stations. The inversion procedure assumes constant Qi in plane layers and finds models which are as nearly constant with depth as possible. We find that the data cannot be explained by a model in which Qi is constant with depth and that the data generally require three-layer models. The resulting models typically give Qi for P waves between 300 and 1000 in the top 5 km, rising to 1000 to 3000 at greater depths, and decreasing to 700 to 1000 around 12 km depth. Qi for S waves is slightly higher in most cases. Because this depth dependence of Qi is generally correlated with the depths of earthquake epicenters, we suggest that Qi may be due to a pressure and temperature-controlled intrinsic attenuation mechanism.

scholarly journals VOLUMETRIC AND SPATIAL SEGMENTATION OF THE TIEN SHAN LITHOSPHERE ACCORDING TO GEOPHYSICAL DATA

2021 ◽  
Vol 12 (3) ◽  
pp. 508-543
Author(s):  
A. K. Rybin ◽  
E. A. Bataleva ◽  
K. S. Nepeina ◽  
V. E. Matyukov
Keyword(s):  
Seismic Wave ◽  
Upper Mantle ◽  
Deep Structure ◽  
Tien Shan ◽  
Geophysical Fields ◽  
S Waves ◽  
Wave Velocities ◽  
Study Results ◽  
Seismic Wave Velocities ◽  
Fault Structures

This article consolidates the results of studying the deep structure of the lithosphere of the Central Tien Shan, which aimed to identify the main tectonic elements in its geophysical models. We have compared the structural and geological data with the information on the deep structure obtained by geophysical methods and from the positions of earthquake hypocenters in the study area. According to geological concepts, the Tien Shan orogenic belt is characterized by longitudinal and transverse segmentation. The boundaries of the Northern, Middle, Southern Western and Eastern segments of the Tien Shan are deep-seated fault structures. In deep faults and channels of heat and mass transfer, endogenous processes are localized. High-velocity, geoelectrical and thermal models consider such faults and channels as contrasting objects that can be referred to as indicators of these processes.Our analysis of the locations of earthquake hypocenters from NNC, KNET, CAIIG, KRNET, SOME catalogues shows that seismic events are strongly confined to the fault zones and the boundaries of large blocks. A correlation between the anomalies of geophysical fields suggests the degree of inheritance of tectonic structures and the boundaries of the main tectonic segments of the Tien Shan. To compare the crustal and upper mantle heterogeneities reflected in different geophysical fields, we have analyzed seismic tomographic sections based on volumetric seismotomographic models geoelectric and velocity sections along profiles across the main tectonic elements of the study area. The sections are used to identify the zones with relatively low (i.e. reduced) seismic wave velocities and detect the deep-seated longitudinal segmentation of the folded belt. Objects showing anomalous seismic wave velocities are found in the seismotomographic sections at all the depths under consideration. The most contrasting differences in the velocities of P- and S-waves are typical of the depths of 0-5 km and 50-65 km, showing the most clearly observed Northern, Southern and Western segments of the Tien Shan. In general, the velocities of P- and S-waves at the Northern Tien Shan are higher than those at the Middle and Southern segments. We have analyzed the distribution of geoelectric heterogeneities identified from magnetotelluric sounding data in order to determine the boundaries of the main tectonic elements that are considered as the zones of increased electrical conductivity confined to the boundaries of the fault structures. The distribution of earthquake epicenters clearly reflects the segmentation of the Tien Shan into the Northern, Middle and Southern segments and shows the Western and Eastern Tien Shan relative to the Talas-Fergana fault. Ourstudies of the crust and the upper mantle of the Tien Shan have confirmed that the abovementioned tectonic segments have differences in their deep structures Based on a comprehensive analysis of the study results, we can qualitatively identify a relationship between the distribution of the velocity and geoelectric heterogeneities in the crust and upper mantle, seismicity and the stress-strain state of the crust.

Relation between P- and S-wave corner frequencies in the seismic spectrum

1974 ◽  
Vol 64 (6) ◽  
pp. 1621-1627 ◽  
Author(s):  
J. C. Savage
Keyword(s):  
High Frequency ◽  
Body Wave ◽  
Fault Model ◽  
P Wave ◽  
Corner Frequency ◽  
Rupture Propagation ◽  
S Wave ◽  
P Waves ◽  
Fault Surface ◽  
S Waves

abstract A comprehensive set of body-wave spectra has been calculated for the Haskell fault model generalized to a circular fault surface. These spectra are used to show that in practice the P-wave corner frequency (ƒp) may exceed the S-wave corner frequency (ƒs) when near-sonic or transonic rupture propagation obtains. The explanation appears to be that in such cases ƒs is so large that it is not identified within the recorded band, but rather a secondary corner is mistaken for ƒs. As a consequence of failing to detect the true asymptotic trend, the high-frequency falloff of the spectrum with frequency is substantially less for S waves than for P waves. This explanation appears to be consistent with the demonstration by Molnar, Tucker, and Brune (1973) that ƒp may exceed ƒs.

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