This article describes an open-source site database for a total number of 1742 earthquake recording sites in the K-NET (Kyoshin network) and KiK-net (Kiban Kyoshin network) networks in Japan. This database contains site characterization parameters directly derived from available velocity profiles, including average wave velocities, bedrock depths, and velocity contrast. Meanwhile, it also consists of earthquake horizontal-to-vertical spectral ratio (HVSR) and peak parameters, for example, peak frequency, amplitude, width, and prominence. In addition, the site database also comprises topographic and geological proxies inferred from regional models or maps. Each parameter is derived in a consistent manner for all sites. This site database can benefit the application of machine learning techniques in studies on site amplification. Besides, it can facilitate, for instances, the search of the optimal site parameter(s) for the prediction of site amplification, the development and testing of ground-motion models or methodologies, as well as investigations on spatial or regional variability in site response. All resources (the site database, earthquake HVSR data at all sites, and the MATLAB script for peak identification) can be freely accessed via: https://doi.org/10.5880/GFZ.2.1.2020.006
ABSTRACT The 1400 km long North Anatolian Fault Zone in Türkiye runs through numerous densely populated regions, including the city of Düzce that was recently hit by an Mw 6.1 earthquake on 23 November 2022. This was the first moderate event in the region after the devastating Mw 7.2 earthquake in 1999, which cost the lives of over 700 people. Despite its moderate size, the earthquake caused unexpected severe damage to a significant number of buildings, as reported by local institutions (Disaster and Emergency Management Presidency, AFAD). It is well established that ground motions in the near field can lead to increased damage due to near-field domain effects, such as ground-motion pulses and directivity effects (i.e., when the site is aligned with rupture propagation). We examine potential near-field effects using the strong ground motion database of AFAD-Turkish Accelerometric Database and Analysis Systems. To achieve this, we first analyze the behavior of the ground-motion intensities in terms of their spatial distribution and observe higher peak ground velocity than expected by ground-motion models in spatially constrained azimuthal ranges. Furthermore, we find that the majority of the near-fault recordings contain velocity pulses that are primary concentrated on the fault-parallel component. This outcome questions the widely accepted understanding from the previous studies, which mainly suggested that impulsive ground motions that are associated with directivity effects primarily occur on the fault-normal component of large-magnitude events.
<p>Ground response analyses (GRA) model the vertical propagation of SH waves through flat-layered media (1DSH) and are widely carried out to evaluate local site effects in practice. Horizontal-to-vertical spectral ratio (HVSR) technique is a cost-effective approach to extract certain site-specific information, e.g., site resonant frequency, but HVSR values cannot be directly used to approximate the level of S-wave amplification. Motivated by the work of Kawase et al. (2019), we propose a procedure to correct earthquake HVSR amplitude for direct amplification estimation. The empirical correction, in essence, compensates HVSR by generic vertical amplifications grouped by vertical fundamental resonant frequency (f<sub>0v</sub>) and 30 m average shear-wave velocity (V<sub>S30</sub>) via k-mean clustering. In this investigation, we evaluate the effectiveness of the corrected HVSR in approximating observed amplification in comparison with 1DSH modelling. To the end, we select a total of 90 KiK-net surface-downhole recording sites which are found to have no velocity contrasts below downhole sensor and thus of which surface-to-borehole spectral ratio (SBSR) can be taken as its empirical transfer function (ETF). 1DSH-based theoretical transfer function (TFF) is computed in the linear domain considering the uncertainty in V<sub>S</sub> profile through randomization. Five goodness-of-fit metrics are adopted to gauge the closeness between observed (ETF) and predicted (i.e., TTF and corrected HVSR) amplifications in both amplitude and spectral shape. The major finding of this study is that the empirical correction procedure to HVSR is highly effective, and the corrected HVSR has a &#8220;good match&#8221; in both spectral shape (Pearson&#8217;s r > 0.6) and amplitude (Index of agreement d > 0.6) at 74% of the investigated sites, as opposed to 17% for 1DSH modelling. In addition, the HVSR-based empirical correction does not need a site model and thus has great potentials in site-specific seismic hazard assessments.</p>
Research Article| November 01, 2013 First Steps toward a Reassessment of the Seismic Risk of the City of Dushanbe (Tajikistan) Marco Pilz; Marco Pilz aHelmholtz Center Potsdam, German Research Center for Geosciences, Helmholtzstr. 7, 14467 Potsdam, Germanypilz@gfz-potsdam.de Search for other works by this author on: GSW Google Scholar Dino Bindi; Dino Bindi aHelmholtz Center Potsdam, German Research Center for Geosciences, Helmholtzstr. 7, 14467 Potsdam, Germanypilz@gfz-potsdam.de Search for other works by this author on: GSW Google Scholar Tobias Boxberger; Tobias Boxberger aHelmholtz Center Potsdam, German Research Center for Geosciences, Helmholtzstr. 7, 14467 Potsdam, Germanypilz@gfz-potsdam.de Search for other works by this author on: GSW Google Scholar Farhod Hakimov; Farhod Hakimov bInstitute of Geology, Earthquake Engineering and Seismology, Academy of Sciences of the Republic of Tajikistan, Ayni Street 267, 734063 Dushanbe, Tajikistan Search for other works by this author on: GSW Google Scholar Bolot Moldobekov; Bolot Moldobekov cCentral Asian Institute for Applied Geosciences, Timur Frunze Street 73/2, 720027 Bishkek, Kyrgyzstan Search for other works by this author on: GSW Google Scholar Shohrukh Murodkulov; Shohrukh Murodkulov bInstitute of Geology, Earthquake Engineering and Seismology, Academy of Sciences of the Republic of Tajikistan, Ayni Street 267, 734063 Dushanbe, Tajikistan Search for other works by this author on: GSW Google Scholar Sagynbek Orunbaev; Sagynbek Orunbaev cCentral Asian Institute for Applied Geosciences, Timur Frunze Street 73/2, 720027 Bishkek, Kyrgyzstan Search for other works by this author on: GSW Google Scholar Massimiliano Pittore; Massimiliano Pittore aHelmholtz Center Potsdam, German Research Center for Geosciences, Helmholtzstr. 7, 14467 Potsdam, Germanypilz@gfz-potsdam.de Search for other works by this author on: GSW Google Scholar Jacek Stankiewicz; Jacek Stankiewicz aHelmholtz Center Potsdam, German Research Center for Geosciences, Helmholtzstr. 7, 14467 Potsdam, Germanypilz@gfz-potsdam.de Search for other works by this author on: GSW Google Scholar Shahid Ullah; Shahid Ullah aHelmholtz Center Potsdam, German Research Center for Geosciences, Helmholtzstr. 7, 14467 Potsdam, Germanypilz@gfz-potsdam.de Search for other works by this author on: GSW Google Scholar Firoz Verjee; Firoz Verjee dAga Khan Development Network, Disaster Risk Management Initiative, Ayni Street 24a, 730025 Dushanbe, Tajikistan Search for other works by this author on: GSW Google Scholar Marc Wieland; Marc Wieland aHelmholtz Center Potsdam, German Research Center for Geosciences, Helmholtzstr. 7, 14467 Potsdam, Germanypilz@gfz-potsdam.de Search for other works by this author on: GSW Google Scholar Pulat Yasunov; Pulat Yasunov bInstitute of Geology, Earthquake Engineering and Seismology, Academy of Sciences of the Republic of Tajikistan, Ayni Street 267, 734063 Dushanbe, Tajikistan Search for other works by this author on: GSW Google Scholar Stefano Parolai Stefano Parolai aHelmholtz Center Potsdam, German Research Center for Geosciences, Helmholtzstr. 7, 14467 Potsdam, Germanypilz@gfz-potsdam.de Search for other works by this author on: GSW Google Scholar Seismological Research Letters (2013) 84 (6): 1026–1038. https://doi.org/10.1785/0220130040 Article history first online: 14 Jul 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Marco Pilz, Dino Bindi, Tobias Boxberger, Farhod Hakimov, Bolot Moldobekov, Shohrukh Murodkulov, Sagynbek Orunbaev, Massimiliano Pittore, Jacek Stankiewicz, Shahid Ullah, Firoz Verjee, Marc Wieland, Pulat Yasunov, Stefano Parolai; First Steps toward a Reassessment of the Seismic Risk of the City of Dushanbe (Tajikistan). Seismological Research Letters 2013;; 84 (6): 1026–1038. doi: https://doi.org/10.1785/0220130040 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySeismological Research Letters Search Advanced Search The country of Tajikistan is located in the Asia–India continental collision zone where the northward‐moving Indian plate indents the Eurasian plate (Molnar and Tapponnier, 1975). The Asian lithosphere being impinged upon by the shallow northward underthrusting Indian lithosphere has resulted in high‐mountain topography, which is subject to active deformation and contemporary faulting, and, consequentially, frequent earthquakes (e.g., Gubin, 1960; Burtman and Molnar, 1993). According to the Global Seismic Hazard Map (Giardini, 1999), almost the entire country exhibits a high‐hazard level with intensities of VIII–IX for a 5% exceedance in 50 years. Most of the... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Abstract Microtremor array measurements, and passive surface wave methods in general, have been increasingly used to non-invasively estimate shear-wave velocity structures for various purposes. The methods estimate dispersion curves and invert them for retrieving S-wave velocity profiles. This paper summarizes principles, limitations, data collection, and processing methods. It intends to enable students and practitioners to understand the principles needed to plan a microtremor array investigation, record and process the data, and evaluate the quality of investigation result. The paper focuses on the spatial autocorrelation processing method among microtremor array processing methods because of its relatively simple calculation and stable applicability. Highlights 1. A summary of fundamental principles of calculating phase velocity from ambient noise 2. General recommendations for MAM data collection and processing using SPAC methods 3. A discussion of limitations and uncertainties in the methods
Seismic noise is generally considered as a reproducible and temporarily stationary natural source of energy. We present a study on the statistical features of the soil motion due to the seismic noise wavefield and the dependencies on the near-surface geology. We have investigated the variations of the 3-D average squared soil displacement over different timescales. The results clearly indicate ballistic behaviour for short timescales being indicative for the properties of the shallow material. Differences in the structural heterogeneity of the subsoil produce different scattering properties, changing the character of motion from nearly ballistic to diffusive on frequency-dependent timescales for all materials. Although in a strict sense the seismic noise wavefield is not completely isotropic, an ultimate pre-condition for a diffusive wavefield, the deviations compared to a uniform distribution are rather small. This means that the emergence of the Green's function is effective for all network sites after a sufficient self-averaging process that is provided by the scattering and the random spatial-temporal noise source distribution.
ABSTRACT Site-specific seismic hazard studies require the knowledge of the shear-wave velocity VS and the high-frequency site attenuation parameter κ0 at the reference rock level at depth. The latter one (called κ0,ref) is often not available and hard to derive. In this study, we make use of the KiK-net database in Japan that consists of surface and colocated downhole sensors. We select 175 sites where the bottom sensor is deployed at rock or hard-rock conditions resulting in a database with many recordings at VS≥1500 m/s. This allows us to tackle two questions: first, is it possible to derive κ0,ref from surface recordings? Second, does κ0 reach an asymptotic level at high VS that could be used as a κ0,ref in site-specific seismic hazard studies? Our results show that measures of κ0 derived from S and coda waves are equivalent. Thus, it is not possible to obtain κ0,ref from surface recordings using coda waves. On the other hand, S-wave measurements of κ0 from surface rock sites are close to κ0,ref if VS≥760 m/s or if the sedimentary cover is thin. The values of κ0 decrease with increasing VS and reach an asymptotic value. The scatter in the so obtained κ0,ref is high, but it can be reduced by selecting subregions with similar geological conditions. Finally, we observe that borehole and surface κ0 are correlated, and that the variability of κ0,ref is only slightly reduced compared to κ0 at the surface. Although we cannot exclude any influence of source effects, our findings indicate that κ0,ref has to be considered as a deep site parameter.
