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This study investigates regional ground-motion characteristics in Yunnan Province using 1,065 recordings from 60 small-to-moderate earthquakes (3.0 ≤  M w ≤ 6.0) at 65 stations. A generalized inversion technique (GIT) using empirical reference site was applied to four tectonically distinct subregions (A–D). The inversion results reveal stress drops (Δ σ ) ranging from 0.3 to 7.34 MPa, with the highest averages in Regions C and D (2.21 MPa), followed by Region A (2.07 MPa) and Region B (1.16 MPa). Δ σ shows no clear dependence on moment magnitude ( M w ) or focal depth but correlates with surface heat flow. Reverse-faulting events exhibit a higher average Δ σ than strike-slip and normal-faulting events. Quality factor models for the four study areas (A–D) are 118.41 f 0.691 , 120.26 f 0.638 , 77.20 f 0.598 and 72.19 f 0.861 , respectively. The eastern regions (C and D) exhibit lower Q 0 and stronger S-wave attenuation, along with higher tectonic activity and lower surface heat flow. The predominant frequencies of average site amplification for GMX-A, GMX-B, GMX-C and GMX-D are 20.00 Hz, 10.83 Hz, 3.97 Hz, and 1.92 Hz, with corresponding amplification factors of 2.84, 4.31, 5.45, and 7.69. Finally, the inversion parameters were validated through stochastic finite-fault simulations of the 2009 M S 6.3 Yao’an mainshock.

Site amplification is an important component of strong ground motion prediction as it differs among sites, reflecting its specific local subsurface geology. Here, we confirm that site amplifications are similar in a neighborhood area over a long period. However, few studies have investigated the spatial properties in a wide region (i.e., the whole of Japan). In this study, we explored the spatial properties of site amplifications based on the generalized inversion technique (GIT) using Fourier amplitude spectra (FAS) as well as pseudo-velocity response spectra (pSv) as the latter is an important index for engineering purposes and the most similar type of response spectra to FAS. The spatial distributions of S-wave site amplifications (SA-S), especially within large sediment basins (e.g., the Kanto and Osaka Basins in Japan), were found to be relatively similar in proximate areas for a long period ranging from 2 to 8 s. This suggests that we could easily predict the site amplifications using an empirical approach through spatial interpolation based on the properties obtained by the GIT. Furthermore, we propose a prediction procedure for site amplification for the whole duration from the SA-S at an arbitrary site. We used the correction function, which converts the SA-S to the site amplification for the whole duration (SA-W), including an S-wave portion and a subsequent portion. This function is called the whole-duration to S-wave spectral ratio (WSR) and is stable in terms of spatial properties. As we could estimate the SA-S either by theoretical transfer functions or observed microtremors, we can easily predict the SA-W based on the proposed WSR concept. We found that SA-S in pSv is more or less similar to SA-S in FAS, however, SA-W in pSv fails to capture the effects of the long duration of ground motions inside a large basin so that we cannot recommend to use pSv for the prediction of whole duration of ground motion.

In low to moderate seismic regions such as the Korean peninsula, it is difficult to perform seismic hazard analyses to construct hazard maps and curves because only a limited number of strong ground motion records is available. In this study, to solve such obstacles, ground motions are simulated using a stochastic model for Fourier amplitude spectrum (FAS) in frequency domain and shaping window model in time domain. The generalized inversion technique is adopted to determine the seismological characteristics (source, path, and site effects) of the FAS for Korean region. The validity of the source, path, and site effects obtained from the GIT and that of simulated ground motions is verified.

The generalized inversion of S-wave amplitude spectra from the free-field strong motion recordings of the China National Strong Motion Observation Network System （NSMONS） are used to evaluate the site effects in the Wenchuan area. In this regard, a total of 602 recordings from 96 aftershocks of the Wenchuan earthquake with magnitudes of M3.7-M6.5 were selected as a dataset. These recordings were obtained from 28 stations at a hypocenter distance ranging from 30 km to 150 km. The inversion results have been verified as reliable by comparing the site response at station 62WUD using the Generalized Inversion Technique （GIT） and the Standard Spectral Ratio method （SSR）. For all 28 stations, the site predominant frequency F and the average site amplification in different frequency bands of 1.0-5.0 Hz, 5.0-10.0 Hz and 1.0-10.0 Hz have been calculated based on the inversion results. Compared with the results from the horizontal-to-vertical spectral ratio （HVSR） method, it shows that the HVSR method can reasonably estimate the site predominant frequency but underestimates the site amplification. The linear fitting between the average site amplification for each frequency band and the V20 （the average uppermost-20 m shear wave velocity） shows good correlation. A distance measurement called the asperity distance DAspt is proposed to reasonably characterize the source-to-site distance for large earthquakes. Finally, the inversed site response is used to identify the soil nonlinearity in the main shock and aftershocks of Wenchuan earthquake. In ten of the 28 stations analyzed in the main shock, the soil behaved nonlinearly, where the ground motion level is apparently beyond a threshold ofPGA 〉 300 cm/s^2 or PGV 〉 20 cm/s, and only one station coded 51SFB has evidence of soil nonlinear behavior in the aftershocks.

We analyzed 1764 records from 322 micro- and moderate-size local earthquakes in the central west Turkey to separate source, site and near-surface attenuation effects by utilizing a generalized inversion technique (GIT) to the spectra. GIT site transfer functions were compared with horizontal-to-vertical spectral ratio (HVSR) estimates by Akyol et al. (Pure Appl Geophys 170(12):2107–2125. doi: 10.1007/s00024-013-0661-2 , 2013 ). Large amplitude values of vertical component GIT site transfer functions were obtained at different frequency bands for some of the sites. These results imply contaminations of HVSR estimates due to basin geometry induced waves caused by deep or shallow lateral heterogeneities. GIT source function estimates were interpreted as Brune source model. Weak epicentral dependence of near-surface attenuation parameter κ with large scattering could be attributed to the source and propagation path complexities along different paths arriving to the stations. Large f e values with large κ 0 values emphasize near-surface weathered zones attenuation effect at high frequencies.

We exploit S-wave spectral amplitudes from 112 aftershocks (3.0 ≤ M L  ≤ 5.3) of the L’Aquila 2009 seismic sequence recorded at 23 temporary stations in the epicentral area to estimate the source parameters of these events, the seismic attenuation characteristics and the site amplification effects at the recording sites. The spectral attenuation curves exhibit a very fast decay in the first few kilometers that could be attributed to the large attenuation of waves traveling trough the highly heterogeneous and fractured crust in the fault zone of the L’Aquila mainshock. The S-waves total attenuation in the first 30 km can be parameterized by a quality factor Q S (f) = 23 f 0.58 obtained by fixing the geometrical spreading to 1/R. The source spectra can be satisfactorily modeled using the omega-square model that provides stress drops between 0.3 and 60 MPa with a mean value of 3.3±2.8 MPa. The site responses show a large variability over the study area and significant amplification peaks are visible in the frequency range from 1 to more than 10 Hz. Finally, the vertical component of the motion is amplified at a number of sites where, as a consequence, the horizontal-to-vertical spectral ratios (HVSR) method fails in detecting the amplitude levels and in few cases the resonance frequencies.

An inversion method was applied to crustal earthquakes dataset to find S-wave attenuation characteristics beneath the Eastern Tohoku region of Japan. Accelerograms from 85 shallow crustal earthquakes up to 25 km depth and magnitude range between 3.5 and 5.5 were analyzed to estimate the seismic quality factor Qs. A homogeneous attenuation model Qs for the wave propagation path was evaluated from spectral amplitudes, at 24 different frequencies between 0.5 and 20 Hz by using generalized inversion technique. To do this, non-parametric attenuation functions were calculated to observe spectral amplitude decay with hypocentral distance. Then, these functions were parameterized to estimate Qs. It was found that in Eastern Tohoku region, the Qs frequency dependence can be approximated with the function 33 f 1.22 within a frequency range between 0.5 and 20 Hz. However, the frequency dependence of Qs in the frequency range between 0.5 and 6 Hz is best approximated by Qs （f） = 36 f 0.94 showing relatively weaker frequency dependence as compared to the relation Qs （f） = 6 f^ 2.09 for the frequency range between 6 and 15 Hz. These results could be used to estimate source and site parameters for seismic hazard assessment in the region.

--Thirty-three earthquakes which occurred in the Central Apennines (Italy) with Ml ranging from 2.4 to 3.7 have been spectrally analysed using digital recordings from twelve stations of the Rete Sismometrica Marchigiana (RSM) network. Data corrected for geometrical spreading and quality factor Q have been inverted by means of the Generalised Inversion Technique. Site responses have been compared with those obtained by H/V ratio. Site amplifications have been observed both at stations placed on Pleistocene sediments and at one station located at 1800m altitude. Source parameters have been calculated by fitting the spectra with an automatic procedure adopting the ω^sup 2^ source model. The seismic moments range from 9.23×10^sup 19^ to 4.28×10^sup 21^ dyne-cm with an average M ^sub 0^ (S) to M ^sub 0^ (P) ratio of 1.13±0.38. The stress drops are generally low and they vary between 1.1 and 10.2bar when estimated by using S source spectra, and between 0.5 and 7.1bar when the P-source spectra are fitted. For the considered range of seismic moments we observe that the stress drop does not have significant dependence on event size.[PUBLICATION ABSTRACT]

In computational seismology, receiver functions represent the impulse response for the earth structure beneath a seismic station and, in general, these are functionals that show several seismic phases in the time-domain related to discontinuities within the crust and the upper mantle. This paper introduces a new technique called generalized pattern search (GPS) for inverting receiver functions to obtain the depth of the crust–mantle discontinuity, i.e., the crustal thickness H, and the ratio of crustal P-wave velocity Vp to S-wave velocity Vs. In particular, the GPS technique, which is a direct search method, does not need derivative or directional vector information. Moreover, the technique allows simultaneous determination of the weights needed for the converted and reverberated phases. Compared to previously introduced variable weights approaches for inverting H-κ stacking of receiver functions, with κ = Vp/Vs, the GPS technique has some advantages in terms of saving computational time and also suitability for simultaneous determination of crustal parameters and associated weights. Finally, the technique is tested using seismic data from the East Africa Rift System and it provides results that are consistent with previously published studies.

We describe an algorithm based upon the Sherman-Morrison-Woodbury formula for the inversion of matrices with special structure that occur in formulae for deletion diagnostics. Substantial computational savings relative to a method based upon Cholesky's decomposition are illustrated. The result has broad application to regression diagnostics for clustered data.