Determination of shallow S-wave velocity profile using microtremor horizontal-to-vertical spectral ratio and surface S-wave velocity with assumption of linear velocity increase.

P-wave velocity and S-wave velocity have been investigated in the Bali Province by using earthquake case studies on March 22, 2017. The study was focused on finding out whether there were anomalies in the values of vp/vs before and after the earthquake. Earthquake data was obtained from the Meteorology, Climatology and Geophysics Agency (BMKG) Region III Denpasar, which consisted of the main earthquake on March 22, 2017 and earthquake data in August 2016 to May 2017. Data was processed using the wadati diagram method, obtained that the vp/vs on SRBI, IGBI, DNP and RTBI stations are shifted from 1.5062 to 1.8261. Before the earthquake occurred the anomaly of the value of vp/vs was found on the four stations, at the SRBI station at 10.35%, at the IGBI station at 16.16%, at DNP station at 12.27% and at RTBI station at 4.62%.

Download Full-text

Tuning S-Wave Velocity Structure of Deep Sedimentary Layers in the Shimousa Region of the Kanto Basin, Japan, Using Autocorrelation of Strong-Motion Records

Bulletin of the Seismological Society of America ◽

10.1785/0120200156 ◽

2020 ◽

Vol 110 (6) ◽

pp. 2882-2891

Author(s):

Kosuke Chimoto ◽

Hiroaki Yamanaka

Keyword(s):

Wave Velocity ◽

Velocity Structure ◽

Strong Motion ◽

S Wave ◽

Reflected Waves ◽

Arrival Times ◽

Strong Motion Records ◽

Kanto Basin ◽

Determination Of Parameters

ABSTRACT The autocorrelation of ambient noise is used to capture reflected waves for crustal and sedimentary structures. We applied autocorrelation to strong-motion records to capture the reflected waves from sedimentary layers and used them for tuning the S-wave velocity structure of these layers. Because a sedimentary-layered structure is complicated and generates many reflected waves, it is important to identify the boundary layer from which the waves reflected. We used spectral whitening during autocorrelation analysis to capture the reflected waves from the seismic bedrock with an appropriate smoothing band, which controls the wave arrival from the desired layer boundary. The effect of whitening was confirmed by the undulation frequency observed in the transfer function of the sedimentary layers. After careful determination of parameters for spectral whitening, we applied data processing to the strong-motion records observed at the stations in the Shimousa region of the Kanto Basin, Japan, to estimate the arrival times of the reflected waves. The arrival times of the reflected waves were found to be fast in the northern part of the Shimousa region and slow in the western and southern parts. These arrival times are consistent with those obtained using existing models. Because we observed a slight difference in the arrival times, the autocorrelation function at each station was used for tuning the S-wave velocity structure model of the sedimentary layers using the inversion technique. The tuned models perfectly match the autocorrelation functions in terms of the arrival time of the reflected waves from the seismic bedrock.

Download Full-text

Determination of the crustal structure and seismicity of the Linfen rift with S-wave velocity mapping

Frontiers of Earth Science ◽

10.1007/s11707-019-0804-6 ◽

2020 ◽

Vol 14 (3) ◽

pp. 647-659

Author(s):

Zigen Wei ◽

Risheng Chu ◽

Meiqin Song ◽

Xiaolin Yang ◽

Shanshan Wu ◽

...

Keyword(s):

Wave Velocity ◽

Crustal Structure ◽

S Wave ◽

Velocity Mapping

Download Full-text

Seismological constraints on ice properties at Dome C, Antarctica, from horizontal to vertical spectral ratios

Antarctic Science ◽

10.1017/s0954102010000325 ◽

2010 ◽

Vol 22 (5) ◽

pp. 572-579 ◽

Cited By ~ 6

Author(s):

Jean-Jacques Lévêque ◽

Alessia Maggi ◽

Annie Souriau

Keyword(s):

Wave Velocity ◽

Spectral Ratio ◽

Seismic Signal ◽

Main Peak ◽

Spectral Ratios ◽

S Wave ◽

Soil Response ◽

Ice Cap ◽

Antarctic Continent ◽

The Antarctic

AbstractThe French-Italian Concordia (CCD) seismological station at Dome C is one of two observatories setup on the ice cap in the interior of the Antarctic continent. We analysed the seismic signal due to ambient noise at this station and at three temporary stations 5 km away from Concordia, in order to specify the ice properties beneath them. A method based on the horizontal to vertical (H/V) spectral ratio, commonly used to analyse soil response in seismic regions, was applied to the Antarctic stations. The main peak in the spectral ratios is observed at frequencies 6.7–8 Hz at the Dome C stations, but it is not observed at another station on the ice cap, QSPA, where the sensor is buried at 275 m depth. This peak can be explained by a 23 m thick unconsolidated snow or firn layer with a low S-wave velocity of 0.7 km s-1, overlying a consolidated layer with S-wave velocity 1.8 km s-1. Despite the non-uniqueness of the solutions obtained by fitting the H/V spectra, this model is preferred because the depth of the velocity contrast coincides with the density at which ice particles arrange themselves in a continuous, dense lattice. A small variability of this structure is observed around Dome C.

Download Full-text