Spatial Variation and Frequency Dependence of Lg Wave Attenuation with Site Response Correction Along the CCSE Array in Central California, US

In this paper, Lg wave records of 43 strong aftershocks in the northern segment of Wenchuan aftershock area recorded by 25 stations of Shaanxi digital network are used. Based on spectral ratio method, a joint inversion method is used to obtain parameters of Lg wave attenuation and site response. In the range of 0.5~7 Hz, the Lg wave attenuation coefficient corresponding to UD, EW and NS components are γ(f)=0.0045f0.327,γ(f)=0.0034f0.417 and γ(f)=0.0036f0.393, respectively. The results show that all stations have site effects lower than 5 in the low frequency, the stations in the Weihe basin as Lint, Jyat and etc do not show obvious amplification, but the stations in the Qinling Mountain show obvious amplification in the high frequencies. At the same time, the results mentioned above are also compared with the that retrieved from small earthquakes.

Download Full-text

Regional attenuation models in Central and Eastern North America using the NGA-East database

Earthquake Spectra ◽

10.1177/87552930211018704 ◽

2021 ◽

pp. 875529302110187

Author(s):

Jeff Bayless

Keyword(s):

North America ◽

Frequency Dependence ◽

Gulf Coast ◽

Site Response ◽

Epistemic Uncertainty ◽

Amplitude Spectrum ◽

Active Regions ◽

Atlantic Coastal Plain ◽

Eastern North America ◽

Anelastic Attenuation

The anelastic attenuation term found in ground motion prediction equations (GMPEs) represents the distance dependence of the effect of intrinsic and scattering attenuation on the wavefield as it propagates through the crust and contains the frequency-dependent quality factor, [Formula: see text], which is an inverse measure of the effective anelastic attenuation. In this work, regional estimates of [Formula: see text] in Central and Eastern North America (CENA) are developed using the NGA-East regionalization. The technique employed uses smoothed Fourier amplitude spectrum (FAS) data from well-recorded events in CENA as collected and processed by NGA-East. Regional [Formula: see text] is estimated using an assumption of average geometrical spreading applicable to the distance ranges considered. Corrections for the radiation pattern effect and for site response based on [Formula: see text] result in a small but statistically significant improvement to the residual analysis. Apparent [Formula: see text] estimates from multiple events are combined within each region to develop the regional models. Models are provided for three NGA-East regions: the Gulf Coast, Central North America, and the Appalachian Province. Consideration of the model uncertainties suggests that the latter two regions could be combined. There were not sufficient data to adequately constrain the model in the Atlantic Coastal Plain region. Tectonically stable regions are usually described by higher [Formula: see text] and weaker frequency dependence ([Formula: see text]), while active regions are typically characterized by lower [Formula: see text] and stronger frequency dependence, and the results are consistent with these expectations. Significantly different regional [Formula: see text] is found for events with data recorded in multiple regions, which supports the NGA-East regionalization. An inspection of two well-recorded events with data both in the Mississippi embayment and in southern Texas indicates that the Gulf Coast regionalization by Cramer in 2017 may be an improvement to that of NGA-East for anelastic attenuation. The [Formula: see text] models developed serve as epistemic uncertainty alternatives in CENA based on a literature review and a comparison with previously published models.

Download Full-text

Lg attenuation, frequency dependence and relative site response of the western United States as revealed by the EarthScope Transportable Array

Geophysical Journal International ◽

10.1093/gji/ggx145 ◽

2017 ◽

Vol 209 (3) ◽

pp. 1955-1971 ◽

Cited By ~ 4

Author(s):

Andrea Gallegos ◽

Nishath Ranasinghe ◽

James Ni ◽

Eric Sandvol

Keyword(s):

United States ◽

Frequency Dependence ◽

Site Response ◽

Western United States

Download Full-text

Spatial variation of coda wave attenuation using aftershocks of the Al Hoceima earthquake of 24 February, 2004, Morocco

Natural Science ◽

10.4236/ns.2013.58a1009 ◽

2013 ◽

Vol 05 (08) ◽

pp. 72-77 ◽

Cited By ~ 1

Author(s):

Abderrahim Boulanouar ◽

Lahcen El Moudnib ◽

Mimoun Harnafi ◽

Taj-Eddine Cherkaoui ◽

Abdelaali Rahmouni ◽

...

Keyword(s):

Spatial Variation ◽

Wave Attenuation ◽

Coda Wave ◽

Coda Wave Attenuation ◽

Al Hoceima

Download Full-text

Seismic hazard analyses of the Metropolitan Water District Emergency Freshwater Pathway, California

Earthquake Spectra ◽

10.1177/87552930211047608 ◽

2021 ◽

pp. 875529302110476

Author(s):

Ivan Wong ◽

Patricia Thomas ◽

Nora Lewandowski ◽

Jeffrey Unruh ◽

Bob Darragh ◽

...

Keyword(s):

Seismic Hazard ◽

Return Period ◽

San Andreas Fault ◽

Site Response ◽

Fault System ◽

Seismic Sources ◽

Central California ◽

San Andreas ◽

San Andreas Fault System ◽

Water District

The Sacramento-San Joaquin Delta in central California is particularly susceptible to damage in a large earthquake due to the vulnerability of the levees that protect cities, farms, and infrastructure. The Delta is located adjacent to the seismically active San Andreas fault system and is also subject to strong ground shaking from numerous other seismic sources in central California, including faults within the Delta. We performed a probabilistic seismic hazard analysis (PSHA) to provide seismic design ground motions for the Metropolitan Water District (MWD) Emergency Freshwater Pathway. We have evaluated the appropriateness of the Next Generation of Attenuation (NGA)-West2 ground motion models for use in our analyses of the Delta, evaluated shear-wave velocity ( VS) data in the vicinity of the Pathway, and performed site response analyses. The latter was performed to compute the probabilistic hazard at the top of the peat at five sites along the Pathway. The sixth site was located outside the Delta and on firm soil. The probabilistic hazard for the six sites and for a range of return periods of engineering relevance were computed in the PSHA. For a return period of 2500 years, the peak horizontal ground acceleration (PGA) values on peat ranged from 0.40 g to 0.53 g. The seismic sources that control the hazard at these sites vary as a function of return period and spectral frequency, but in general, the closer the sites are to faults within the San Andreas fault system, the higher the hazard.

Download Full-text