Shear wave inversion in a shallow coastal environment

2014 ◽  
Vol 136 (4) ◽  
pp. 2156-2156
Author(s):  
Gopu R. Potty ◽  
Jennifer L. Giard ◽  
James H. Miller ◽  
Christopher D. P. Baxter ◽  
Marcia J. Isakson ◽  
...  
Keyword(s):  
Shear Wave ◽  
Coastal Environment ◽  
Wave Inversion ◽  
Shallow Coastal Environment

The geochemistry of the late Cambrian carbonate in North China: the Steptoean Positive Carbon Isotope Excursion (SPICE) record suppressed in a coastal condition?

2019 ◽  
Vol 156 (10) ◽  
pp. 1805-1819 ◽  
Author(s):  
Jing Huang ◽  
Yali Chen ◽  
Xuelei Chu ◽  
Tao Sun
Keyword(s):  
Sea Level ◽  
Carbon Isotope ◽  
North China ◽  
Coastal Environment ◽  
Sedimentary Records ◽  
Late Cambrian ◽  
Geochemical Proxies ◽  
Carbon Isotope Excursion ◽  
Globally Distributed ◽  
Shallow Coastal Environment

AbstractThe Steptoean Positive Carbon Isotope Excursion (SPICE) is globally distributed in late Cambrian sedimentary records but controversially heterogeneous in its magnitudes. Here we use multiple geochemical proxies to investigate the late Cambrian carbonates from the Tangwangzhai section in North China, which were deposited in a shallow coastal environment with three depositional sequences (S1–S3). Each sequence comprises a transgressive systems tract (TST) and a highstand systems tract (HST). The REE + Y and trace element records are consistent with the depositional condition and indicate that terrigenous influence was more significant in the TST than HST. δ13Ccarb and δ34SCAS are low in the TST relative to HST, consistent with the scenario that terrigenous inputs were profoundly aggressive to seawater by introducing 13C-depleted and 34S-depleted materials. Within the TST of S2, the SPICE excursion shows a scaled-down δ13Ccarb positive shift (∼1.7 ‰) relative to its general records (∼4–6 ‰); the corresponding δ34SCAS show no positive excursion. This ‘atypical’ SPICE record is attributed to enhanced 13C-depleted and 34S-depleted terrigenous influence during the TST, which would reduce the amplitude of δ13Ccarb excursion, and even obscure δ34SCAS excursion. Meanwhile the subaerial unconformity at the base of TST would also cause a partially missing and a ‘snapshot’ preservation. Our study confirms significant local influence to the SPICE records, and further supports the heterogeneity and low sulphate concentrations of the late Cambrian seawater, because of which the SPICE records may be vulnerable to specific depositional conditions (e.g. sea-level, terrigenous input).

Nitrogen isotopic discrimination by water column nitrification in a shallow coastal environment

2008 ◽  
Vol 64 (1) ◽  
pp. 39-48 ◽  
Author(s):  
Ryo Sugimoto ◽  
Akihide Kasai ◽  
Toshihiro Miyajima ◽  
Kouichi Fujita
Keyword(s):  
Water Column ◽  
Coastal Environment ◽  
Isotopic Discrimination ◽  
Shallow Coastal Environment

Near-surface shear-wave velocity estimation based on surface-wave inversion

2016 ◽  
Vol 35 (11) ◽  
pp. 940-945 ◽  
Author(s):  
Peiming Li ◽  
Kui Zhang ◽  
Yimeng Zhang ◽  
Zhihui Yan
Keyword(s):  
Surface Wave ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Velocity Estimation ◽  
Surface Shear ◽  
Near Surface ◽  
Wave Inversion ◽  
Surface Shear Wave

scholarly journals MAPPING BATHYMETRY BY LANDSAT DATA IN SHALLOW COASTAL ENVIRONMENT (CASE STUDY: THE SOUTHEAST OF THE CASPIAN SEA)

2019 ◽  
Vol XLII-4/W18 ◽  
pp. 83-87
Author(s):  
L. Amini ◽  
A. A. Kakroodi
Keyword(s):  
High Accuracy ◽  
Coastal Environment ◽  
Landsat 8 ◽  
Landsat Data ◽  
Effective Solution ◽  
The Caspian Sea ◽  
Highly Correlated ◽  
Shallow Coastal Environment ◽  
Reflectance Data

Abstract. Compared to traditional methods, remote sensing (RS) technique is an efficient, fast, low-priced and effective solution in bathymetry. In this study, a linear equation was applied between field and reflectance data to achieve bathymetry map. Landsat-8 is characterized by additional visible band compared with previous Landsat bands on coastal zone application, therefore, we apply two regions of spectrum to compare the accuracy of bathymetry, Bands 1, 3, 4 and bands 2, 3 and 4 respectively. Furthermore, Logarithmic transformation also applied on both spectral regions to have bathymetry map. The coefficient obtained from reflectance and filed data was applied on Tm bands to retrieve the bathymetry of Gomishan lagoon in 2000. The results show that the second spectral region, Bands 2, 3 and 4, is highly correlated with filed data and more accurate (R2 = 0.94, RMSE = 0.35). Moreover, there is a relatively high accuracy between the retrieval of Gomishan bathymetry and the report of recent studies.

scholarly journals High-Velocity Surface Layer Effects on Rayleigh Waves: Recommendations for Improved Shear-Wave Velocity Modeling

2020 ◽  
Vol 110 (1) ◽  
pp. 279-287
Author(s):  
Gabriel Gribler ◽  
Lee M. Liberty ◽  
T. Dylan Mikesell
Keyword(s):  
Rayleigh Wave ◽  
Shear Wave ◽  
High Velocity ◽  
Site Response ◽  
Soil Classification ◽  
Cost Effective ◽  
Road Surface ◽  
Geologic Hazard ◽  
Soil Stiffness ◽  
Wave Inversion

ABSTRACT Soil stiffness estimates are critical to geologic hazard and risk assessment in urban centers. Multichannel analysis of surface-wave (MASW) data collection along city streets is now a standard, cost-effective, and noninvasive soil stiffness approximation tool. With this approach, shear-wave velocities (VS) are derived from Rayleigh-wave signals. Although the current MASW practice is to neglect the effect of a high-velocity road layer on soil VS estimates, our models show measurable impacts on Rayleigh-wave amplitudes and phase velocities when seismic data are acquired on a road surface. Here, we compare synthetic models with field MASW and downhole VS measurements. Our modeling indicates that a road layer attenuates Rayleigh-wave signals across all frequencies, introduces coherent higher-mode signals, and leads to overestimated VS and VS30 values. We show that VS30 can be overestimated by more than 7% when soft soils underlie a rigid road surface. Inaccurate VS estimates can lead to improper soil classification and bias earthquake site-response estimates. For road-based MASW data analysis, we recommend incorporating a surface road layer in the Rayleigh-wave inversion to improve VS estimate accuracy with depth.

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