TY - JOUR A1 - Kotha, Sreeram Reddy A1 - Weatherill, Graeme A1 - Bindi, Dino A1 - Cotton, Fabrice T1 - Near-source magnitude scaling of spectral accelerations BT - analysis and update of Kotha et al. (2020) model JF - Bulletin of earthquake engineering : official publication of the European Association for Earthquake Engineering N2 - Ground-motion models (GMMs) are often used to predict the random distribution of Spectral accelerations (SAs) at a site due to a nearby earthquake. In probabilistic seismic hazard and risk assessment, large earthquakes occurring close to a site are considered as critical scenarios. GMMs are expected to predict realistic SAs with low within-model uncertainty (sigma(mu)) for such rare scenarios. However, the datasets used to regress GMMs are usually deficient of data from critical scenarios. The (Kotha et al., A Regionally Adaptable Ground-Motion Model for Shallow Crustal Earthquakes in Europe Bulletin of Earthquake Engineering 18:4091-4125, 2020) GMM developed from the Engineering strong motion (ESM) dataset was found to predict decreasing short-period SAs with increasing M-W >= M-h = 6.2, and with large sigma(mu) at near-source distances <= 30km. In this study, we updated the parametrisation of the GMM based on analyses of ESM and the Near source strong motion (NESS) datasets. With M-h = 5.7, we could rectify the M-W scaling issue, while also reducing sigma(mu). at M-W >= M-h. We then evaluated the GMM against NESS data, and found that the SAs from a few large, thrust-faulting events in California, New Zealand, Japan, and Mexico are significantly higher than GMM median predictions. However, recordings from these events were mostly made on soft-soil geology, and contain anisotropic pulse-like effects. A more thorough non-ergodic treatment of NESS was not possible because most sites sampled unique events in very diverse tectonic environments. We provide an updated set of GMM coefficients,sigma(mu), and heteroscedastic variance models; while also cautioning against its application for M-W <= 4 in low-moderate seismicity regions without evaluating the homogeneity of M-W estimates between pan-European ESM and regional datasets. KW - Ground-motion model KW - Spectral accelerations KW - Magnitude scalin KW - Near-source saturation KW - Within-model uncertainty KW - Heteroscedastic KW - variability Y1 - 2022 U6 - https://doi.org/10.1007/s10518-021-01308-5 SN - 1570-761X SN - 1573-1456 VL - 20 IS - 3 SP - 1343 EP - 1370 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Zhu, Chuanbin A1 - Cotton, Fabrice A1 - Kwak, Dong-Youp A1 - Ji, Kun A1 - Kawase, Hiroshi A1 - Pilz, Marco T1 - Within-site variability in earthquake site response JF - Geophysical journal international N2 - The within-site variability in site response is the randomness in site response at a given site from different earthquakes and is treated as aleatory variability in current seismic hazard/risk analyses. In this study, we investigate the single-station variability in linear site response at K-NET and KiK-net stations in Japan using a large number of earthquake recordings. We found that the standard deviation of the horizontal-to-vertical Fourier spectral ratio at individual sites, that is single-station horizontal-to-vertical spectral ratio (HVSR) sigma sigma(HV,s), approximates the within-site variability in site response quantified using surface-to-borehole spectral ratios (for oscillator frequencies higher than the site fundamental frequency) or empirical ground-motion models. Based on this finding, we then utilize the single-station HVSR sigma as a convenient tool to study the site-response variability at 697 KiK-net and 1169 K-NET sites. Our results show that at certain frequencies, stiff, rough and shallow sites, as well as small and local events tend to have a higher sigma(HV,s). However, when being averaged over different sites, the single-station HVSR sigma, that is sigma(HV), increases gradually with decreasing frequency. In the frequency range of 0.25-25 Hz, sigma(HV) is centred at 0.23-0.43 in ln scales (a linear scale factor of 1.26-1.54) with one standard deviation of less than 0.1. sigma(HV) is quite stable across different tectonic regions, and we present a constant, as well as earthquake magnitude- and distance-dependent sigma(HV) models. KW - earthquake ground motions KW - earthquake hazards KW - site effects Y1 - 2021 U6 - https://doi.org/10.1093/gji/ggab481 SN - 0956-540X SN - 1365-246X VL - 229 IS - 2 SP - 1268 EP - 1281 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Peña, Carlos A1 - Metzger, Sabrina A1 - Heidbach, Oliver A1 - Bedford, Jonathan A1 - Bookhagen, Bodo A1 - Moreno, Marcos A1 - Oncken, Onno A1 - Cotton, Fabrice T1 - Role of poroelasticity during the early postseismic deformation of the 2010 Maule megathrust earthquake JF - Geophysical research letters N2 - Megathrust earthquakes impose changes of differential stress and pore pressure in the lithosphere-asthenosphere system that are transiently relaxed during the postseismic period primarily due to afterslip, viscoelastic and poroelastic processes. Especially during the early postseismic phase, however, the relative contribution of these processes to the observed surface deformation is unclear. To investigate this, we use geodetic data collected in the first 48 days following the 2010 Maule earthquake and a poro-viscoelastic forward model combined with an afterslip inversion. This model approach fits the geodetic data 14% better than a pure elastic model. Particularly near the region of maximum coseismic slip, the predicted surface poroelastic uplift pattern explains well the observations. If poroelasticity is neglected, the spatial afterslip distribution is locally altered by up to +/- 40%. Moreover, we find that shallow crustal aftershocks mostly occur in regions of increased postseismic pore-pressure changes, indicating that both processes might be mechanically coupled. KW - Chilean subduction zone KW - poroelasticity KW - power-law rheology KW - afterslip inversion KW - InSAR KW - GNSS Y1 - 2022 U6 - https://doi.org/10.1029/2022GL098144 SN - 0094-8276 SN - 1944-8007 VL - 49 IS - 9 PB - Wiley CY - Hoboken, NJ ER - TY - JOUR A1 - Gomez-Zapata, Juan Camilo A1 - Pittore, Massimiliano A1 - Cotton, Fabrice A1 - Lilienkamp, Henning A1 - Shinde, Simantini A1 - Aguirre, Paula A1 - Santa Maria, Hernan T1 - Epistemic uncertainty of probabilistic building exposure compositions in scenario-based earthquake loss models JF - Bulletin of Earthquake Engineering N2 - In seismic risk assessment, the sources of uncertainty associated with building exposure modelling have not received as much attention as other components related to hazard and vulnerability. Conventional practices such as assuming absolute portfolio compositions (i.e., proportions per building class) from expert-based assumptions over aggregated data crudely disregard the contribution of uncertainty of the exposure upon earthquake loss models. In this work, we introduce the concept that the degree of knowledge of a building stock can be described within a Bayesian probabilistic approach that integrates both expert-based prior distributions and data collection on individual buildings. We investigate the impact of the epistemic uncertainty in the portfolio composition on scenario-based earthquake loss models through an exposure-oriented logic tree arrangement based on synthetic building portfolios. For illustrative purposes, we consider the residential building stock of Valparaiso (Chile) subjected to seismic ground-shaking from one subduction earthquake. We have found that building class reconnaissance, either from prior assumptions by desktop studies with aggregated data (top-down approach), or from building-by-building data collection (bottom-up approach), plays a fundamental role in the statistical modelling of exposure. To model the vulnerability of such a heterogeneous building stock, we require that their associated set of structural fragility functions handle multiple spectral periods. Thereby, we also discuss the relevance and specific uncertainty upon generating either uncorrelated or spatially cross-correlated ground motion fields within this framework. We successively show how various epistemic uncertainties embedded within these probabilistic exposure models are differently propagated throughout the computed direct financial losses. This work calls for further efforts to redesign desktop exposure studies, while also highlighting the importance of exposure data collection with standardized and iterative approaches. KW - Epistemic uncertainty KW - Sensitivity analysis KW - Scheme KW - Faceted taxonomy KW - Probabilistic exposure modelling KW - Earthquake scenario KW - Data collection KW - Earthquake loss modelling KW - Spatially cross-correlated ground motion KW - fields Y1 - 2022 U6 - https://doi.org/10.1007/s10518-021-01312-9 SN - 1570-761X SN - 1573-1456 N1 - Update notice Correction to: Epistemic uncertainty of probabilistic building exposure compositions in scenario-based earthquake loss models (Bulletin of Earthquake Engineering, (2022), 20, 5, (2401-2438), https://doi.org/10.1007/s10518-021-01312-9) Bulletin of Earthquake Engineering, Volume 20, Issue 5, Pages 2439, March 2022, https://doi.org/10.1007/s10518-022-01340-z VL - 20 IS - 5 SP - 2401 EP - 2438 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Yen, Ming-Hsuan A1 - von Specht, Sebastian A1 - Lin, Yen-Yu A1 - Cotton, Fabrice A1 - Ma, Kuo-Fong T1 - Within- and between-event variabilities of strong-velocity pulses of moderate earthquakes within dense seismic arrays JF - Bulletin of the Seismological Society of America N2 - Ground motion with strong-velocity pulses can cause significant damage to buildings and structures at certain periods; hence, knowing the period and velocity amplitude of such pulses is critical for earthquake structural engineering. However, the physical factors relating the scaling of pulse periods with magnitude are poorly understood. In this study, we investigate moderate but damaging earthquakes (M-w 6-7) and characterize ground- motion pulses using the method of Shahi and Baker (2014) while considering the potential static-offset effects. We confirm that the within-event variability of the pulses is large. The identified pulses in this study are mostly from strike-slip-like earthquakes. We further perform simulations using the freq uency-wavenumber algorithm to investigate the causes of the variability of the pulse periods within and between events for moderate strike-slip earthquakes. We test the effect of fault dips, and the impact of the asperity locations and sizes. The simulations reveal that the asperity properties have a high impact on the pulse periods and amplitudes at nearby stations. Our results emphasize the importance of asperity characteristics, in addition to earthquake magnitudes for the occurrence and properties of pulses produced by the forward directivity effect. We finally quantify and discuss within- and between-event variabilities of pulse properties at short distances. Y1 - 2021 U6 - https://doi.org/10.1785/0120200376 SN - 0037-1106 SN - 1943-3573 VL - 112 IS - 1 SP - 361 EP - 380 PB - Seismological Society of America CY - El Cerito, Calif. ER - TY - JOUR A1 - Zhu, Chuanbin A1 - Cotton, Fabrice A1 - Kawase, Hiroshi A1 - Händel, Annabel A1 - Pilz, Marco A1 - Nakano, Kenichi T1 - How well can we predict earthquake site response so far? BT - site-specific approaches JF - Earthquake spectra : the professional journal of the Earthquake Engineering Research Institute N2 - Earthquake site responses or site effects are the modifications of surface geology to seismic waves. How well can we predict the site effects (average over many earthquakes) at individual sites so far? To address this question, we tested and compared the effectiveness of different estimation techniques in predicting the outcrop Fourier site responses separated using the general inversion technique (GIT) from recordings. Techniques being evaluated are (a) the empirical correction to the horizontal-to-vertical spectral ratio of earthquakes (c-HVSR), (b) one-dimensional ground response analysis (GRA), and (c) the square-root-impedance (SRI) method (also called the quarter-wavelength approach). Our results show that c-HVSR can capture significantly more site-specific features in site responses than both GRA and SRI in the aggregate, especially at relatively high frequencies. c-HVSR achieves a "good match" in spectral shape at similar to 80%-90% of 145 testing sites, whereas GRA and SRI fail at most sites. GRA and SRI results have a high level of parametric and/or modeling errors which can be constrained, to some extent, by collecting on-site recordings. KW - Site response KW - site effects KW - HVSR KW - ground response analysis KW - square-root-impedance KW - earthquake Y1 - 2022 U6 - https://doi.org/10.1177/87552930211060859 SN - 8755-2930 SN - 1944-8201 VL - 38 IS - 2 SP - 1047 EP - 1075 PB - Sage Publ. CY - Thousand Oaks ER - TY - JOUR A1 - Lilienkamp, Henning A1 - von Specht, Sebastian A1 - Weatherill, Graeme A1 - Caire, Giuseppe A1 - Cotton, Fabrice T1 - Ground-Motion modeling as an image processing task BT - introducing a neural network based, fully data-driven, and nonergodic JF - Bulletin of the Seismological Society of America N2 - We construct and examine the prototype of a deep learning-based ground-motion model (GMM) that is both fully data driven and nonergodic. We formulate ground-motion modeling as an image processing task, in which a specific type of neural network, the U-Net, relates continuous, horizontal maps of earthquake predictive parameters to sparse observations of a ground-motion intensity measure (IM). The processing of map-shaped data allows the natural incorporation of absolute earthquake source and observation site coordinates, and is, therefore, well suited to include site-, source-, and path-specific amplification effects in a nonergodic GMM. Data-driven interpolation of the IM between observation points is an inherent feature of the U-Net and requires no a priori assumptions. We evaluate our model using both a synthetic dataset and a subset of observations from the KiK-net strong motion network in the Kanto basin in Japan. We find that the U-Net model is capable of learning the magnitude???distance scaling, as well as site-, source-, and path-specific amplification effects from a strong motion dataset. The interpolation scheme is evaluated using a fivefold cross validation and is found to provide on average unbiased predictions. The magnitude???distance scaling as well as the site amplification of response spectral acceleration at a period of 1 s obtained for the Kanto basin are comparable to previous regional studies. Y1 - 2022 U6 - https://doi.org/10.1785/0120220008 SN - 0037-1106 SN - 1943-3573 VL - 112 IS - 3 SP - 1565 EP - 1582 PB - Seismological Society of America CY - Albany ER - TY - JOUR A1 - Esfahani, Reza Dokht Dolatabadi A1 - Vogel, Kristin A1 - Cotton, Fabrice A1 - Ohrnberger, Matthias A1 - Scherbaum, Frank A1 - Kriegerowski, Marius T1 - Exploring the dimensionality of ground-motion data by applying autoencoder techniques JF - Bulletin of the Seismological Society of America : BSSA N2 - In this article, we address the question of how observed ground-motion data can most effectively be modeled for engineering seismological purposes. Toward this goal, we use a data-driven method, based on a deep-learning autoencoder with a variable number of nodes in the bottleneck layer, to determine how many parameters are needed to reconstruct synthetic and observed ground-motion data in terms of their median values and scatter. The reconstruction error as a function of the number of nodes in the bottleneck is used as an indicator of the underlying dimensionality of ground-motion data, that is, the minimum number of predictor variables needed in a ground-motion model. Two synthetic and one observed datasets are studied to prove the performance of the proposed method. We find that mapping ground-motion data to a 2D manifold primarily captures magnitude and distance information and is suited for an approximate data reconstruction. The data reconstruction improves with an increasing number of bottleneck nodes of up to three and four, but it saturates if more nodes are added to the bottleneck. Y1 - 2021 U6 - https://doi.org/10.1785/0120200285 SN - 0037-1106 SN - 1943-3573 VL - 111 IS - 3 SP - 1563 EP - 1576 PB - Seismological Society of America CY - El Cerito, Calif. ER - TY - JOUR A1 - Türker, Elif A1 - Cotton, Fabrice A1 - Pilz, Marco A1 - Weatherill, Graeme T1 - Analysis of the 2019 Mw 5.8 Silivri earthquake ground motions BT - evidence of systematic azimuthal variations associated with directivity effects JF - Seismological research letters N2 - The main Marmara fault (MMF) extends for 150 km through the Sea of Marmara and forms the only portion of the North Anatolian fault zone that has not ruptured in a large event (Mw >7) for the last 250 yr. Accordingly, this portion is potentially a major source contributing to the seismic hazard of the Istanbul region. On 26 September 2019, a sequence of moderate-sized events started along the MMF only 20 km south of Istanbul and were widely felt by the population. The largest three events, 26 September Mw 5.8 (10:59 UTC), 26 September 2019 Mw 4.1 (11:26 UTC), and 20 January 2020 Mw 4.7 were recorded by numerous strong-motion seismic stations and the resulting ground motions were compared to the predicted means resulting from a set of the most recent ground-motion prediction equations (GMPEs). The estimated residuals were used to investigate the spatial variation of ground motion across the Marmara region. Our results show a strong azimuthal trend in ground-motion residuals, which might indicate systematically repeating directivity effects toward the eastern Marmara region. Y1 - 2022 U6 - https://doi.org/10.1785/0220210168 SN - 0895-0695 SN - 1938-2057 VL - 93 IS - 2A SP - 693 EP - 705 PB - Seismological Society of America CY - Boulder, Colo. ER - TY - JOUR A1 - Durand, Virginie A1 - Bentz, Stephan A1 - Kwiatek, Grzegorz A1 - Dresen, Georg A1 - Wollin, Christopher A1 - Heidbach, Oliver A1 - Martinez-Garzon, Patricia A1 - Cotton, Fabrice A1 - Nurlu, Murat A1 - Bohnhoff, Marco T1 - A two-scale preparation phase preceded an M-w 5.8 earthquake in the sea of marmara offshore Istanbul, Turkey JF - Seismological research letters N2 - We analyze the spatiotemporal evolution of seismicity during a sequence of moderate (an M-w 4.7 foreshock and M-w 5.8 mainshock) earthquakes occurring in September 2019 at the transition between a creeping and a locked segment of the North Anatolian fault in the central Sea of Marmara, northwest Turkey. To investigate in detail the seismicity evolution, we apply a matched-filter technique to continuous waveforms, thus reducing the magnitude threshold for detection. Sequences of foreshocks preceding the two largest events are clearly seen, exhibiting two different behaviors: a long-term activation of the seismicity along the entire fault segment and a short-term concentration around the epicenters of the large events. We suggest a two-scale preparation phase, with aseismic slip preparing the mainshock final rupture a few days before, and a cascade mechanism leading to the nucleation of the mainshock. Thus, our study shows a combination of seismic and aseismic slip during the foreshock sequence changing the strength of the fault, bringing it closer to failure. Y1 - 2020 U6 - https://doi.org/10.1785/0220200110 SN - 0895-0695 SN - 1938-2057 VL - 91 IS - 6 SP - 3139 EP - 3147 CY - Boulder ER -