scholarly journals Estimation of S-wave velocity structures in the southern area of Shizuoka Prefecture by analyzing array data of long-period microtremors and strong motions

2008 ◽  
Vol 61 (6) ◽  
pp. 499-510 ◽  
Author(s):  
Seiji Tsuno ◽  
Kazuyoshi Kudo
Keyword(s):  
Wave Velocity ◽  
S Wave ◽  
Array Data ◽  
Long Period ◽  
Shizuoka Prefecture ◽  
Southern Area

scholarly journals Array data processing techniques applied to long-period shear waves at Fennoscandian seismograph stations

1969 ◽  
Vol 59 (5) ◽  
pp. 1863-1887
Author(s):  
James H. Whitcomb
Keyword(s):  
Data Processing ◽  
Velocity Ratio ◽  
Underground Explosion ◽  
High Signal ◽  
S Wave ◽  
Array Data ◽  
S Waves ◽  
Long Period ◽  
Normal Record ◽  
The Individual

abstract Array data processing is applied to long-period records of S waves at a network of five Fennoscandian seismograph stations (Uppsala, Umeå, Nurmijärvi, Kongsberg, Copenhagen) with a maximum separation of 1300 km. Records of five earthquakes and one underground explosion are included in the study. The S motion is resolved into SH and SV, and after appropriate time shifts the individual traces are summed, both directly and after weighting. In general, high signal correlation exists among the different stations involved resulting in more accurate time readings, especially for records which have amplitudes that are too small to be read normally. S-wave station residuals correlate with the general crustal type under each station. In addition, the Fennoscandian shield may have a higher SH/SV velocity ratio than the adjacent tectonic area to the northwest.SV-to-P conversion at the base of the crust can seriously interfere with picking the onset of Sin normal record reading. The study demonstrates that, for epicentral distances beyond about 30°, existing networks of seismograph stations can be successfully used for array processing of long-period arrivals, especially the S arrivals.

Exploration of Deep S-Wave Velocity Structure in Niigata and Shonai Plains to Estimate Long-period Earthquake Ground Motion

2009 ◽  
Vol 61 (4) ◽  
pp. 191-205
Author(s):  
Hiroaki SATO ◽  
Hiroaki YAMANAKA ◽  
Sadanori HIGASHI ◽  
Kiyotaka SATO ◽  
Yoshiaki SHIBA ◽  
...  
Keyword(s):  
Ground Motion ◽  
Wave Velocity ◽  
Velocity Structure ◽  
Earthquake Ground Motion ◽  
S Wave ◽  
Long Period

scholarly journals Comparing ray-theoretical and finite-frequency teleseismic traveltimes: implications for constraining the ratio of S-wave to P-wave velocity variations in the lower mantle

2020 ◽  
Vol 224 (3) ◽  
pp. 1540-1552
Author(s):  
Carlos A M Chaves ◽  
Jeroen Ritsema ◽  
Paula Koelemeijer
Keyword(s):  
North America ◽  
Wave Velocity ◽  
Lower Mantle ◽  
P Wave ◽  
Finite Frequency ◽  
S Wave ◽  
P Waves ◽  
Long Period ◽  
P Wave Velocity ◽  
The Pacific

SUMMARY A number of seismological studies have indicated that the ratio R of S-wave and P-wave velocity perturbations increases to 3–4 in the lower mantle with the highest values in the large low-velocity provinces (LLVPs) beneath Africa and the central Pacific. Traveltime constraints on R are based primarily on ray-theoretical modelling of delay times of P waves (ΔTP) and S waves (ΔTS), even for measurements derived from long-period waveforms and core-diffracted waves for which ray theory (RT) is deemed inaccurate. Along with a published set of traveltime delays, we compare predicted values of ΔTP, ΔTS, and the ΔTS/ΔTP ratio for RT and finite-frequency (FF) theory to determine the resolvability of R in the lower mantle. We determine the FF predictions of ΔTP and ΔTS using cross-correlation methods applied to spectral-element method waveforms, analogous to the analysis of recorded waveforms, and by integration using FF sensitivity kernels. Our calculations indicate that RT and FF predict a similar variation of the ΔTS/ΔTP ratio when R increases linearly with depth in the mantle. However, variations of R in relatively thin layers (< 400 km) are poorly resolved using long-period data (T > 20 s). This is because FF predicts that ΔTP and ΔTS vary smoothly with epicentral distance even when vertical P-wave and S-wave gradients change abruptly. Our waveform simulations also show that the estimate of R for the Pacific LLVP is strongly affected by velocity structure shallower in the mantle. If R increases with depth in the mantle, which appears to be a robust inference, the acceleration of P waves in the lithosphere beneath eastern North America and the high-velocity Farallon anomaly negates the P-wave deceleration in the LLVP. This results in a ΔTP of about 0, whereas ΔTS is positive. Consequently, the recorded high ΔTS/ΔTP for events in the southwest Pacific and stations in North America may be misinterpreted as an anomalously high R for the Pacific LLVP.

scholarly journals ARRAY MEASUREMENTS OF LONG-PERIOD MICROTREMORS IN THE KANTO PLAIN : Estimation of S-wave velocity structure at Koto

1995 ◽  
Vol 60 (478) ◽  
pp. 99-105 ◽  
Author(s):  
Hiroaki YAMANAKA ◽  
Shinji FURUYA ◽  
Takashi NOZAWA ◽  
Tohru SASAKI ◽  
Tsuyoshi TAKAI
Keyword(s):  
Wave Velocity ◽  
Velocity Structure ◽  
S Wave ◽  
Long Period ◽  
Array Measurements

Long-Period Ground Motions Observed in the Northern Part of Kanto Basin, During the 2011 off the Pacific Coast of Tohoku Earthquake, Japan

2013 ◽  
Vol 8 (sp) ◽  
pp. 781-791 ◽  
Author(s):  
Seiji Tsuno ◽  
◽  
Andi Muhamad Pramatadie ◽  
Yadab P. Dhakal ◽  
Kosuke Chimoto ◽  
...  
Keyword(s):  
Wave Velocity ◽  
Love Wave ◽  
Pacific Coast ◽  
Velocity Structure ◽  
Ground Motions ◽  
Tohoku Earthquake ◽  
S Wave ◽  
Long Period ◽  
The Pacific ◽  
Kanto Basin

During the 2011 off the Pacific coast of Tohoku earthquake (Mw 9.0), strong ground motions were observed at many seismic stations in the Tokyo Metropolitan Area located about 200 km away from the southern edge of the earthquake source fault. Large earthquake responses in high-rise buildings having long natural periods of several seconds were also observed. The largest ground responses for a period of 4 to 5 seconds were observed locally in Oyama (K-NET TCG012) and Koga (K-NET IBR009) on the border between Tochigi and Ibaraki Prefectures in the northern part of Kanto basin. Geophysical information in these areas was not accurate enough, however, to evaluate these ground motions. To understand S-wave velocity structures, we performed array microtremors observations at TCG012 seismic station in Oyama. We applied the Spatial Autocorrelation (SPAC) method to array microtremors data for vertical components. Rayleigh wave phase velocity from 0.3 to 1.6 km/s was obtained for a period of 0.25 to 3 seconds. We inverted phase velocity to a S-wave velocity structure reaching to bedrock at a depth of 1.6 km, using a Genetic Algorithm. The estimated structure explained the first peak of the H/V spectral ratio of microtremors well by the ellipticity of fundamentalmode Rayleigh wave. To evaluate long-period ground motions observed around Oyama during the main shock, we estimated earthquake ground motions by 1-D analysis, showing agreements with and the differences from those observed. As a result, velocity calculated at IBR008 located midway between the Tsukuba Mountains and Oyama, explained that observed for main phases and later phases. However, velocity calculated at TCG012 did not explain that observed for later phases. According to the emphasis of airy phases for group velocity of Love wave using the estimated S-wave velocity structure and the principal axis for later phases obtained by PCA corresponding to the vibration direction of Love wave propagating from the earthquake source fault and through the Tsukuba Mountains, long-period ground motions of a period of 3 to 5 seconds observed at TCG012 lasting for 200 seconds after the arrival of main phases, consist of Love wave.

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