TY - JOUR A1 - Korup, Oliver A1 - Mohr, Christian Heinrich A1 - Manga, Michael M. T1 - Bayesian detection of streamflow response to earthquakes JF - Water resources research : an AGU journal N2 - Detecting whether and how river discharge responds to strong earthquake shaking can be time-consuming and prone to operator bias when checking hydrographs from hundreds of gauging stations. We use Bayesian piecewise regression models to show that up to a fifth of all gauging stations across Chile had their largest change in daily streamflow trend on the day of the M-w 8.8 Maule earthquake in 2010. These stations cluster distinctly in the near field though the number of detected streamflow changes varies with model complexity and length of time window considered. Credible seismic streamflow changes at several stations were the highest detectable in eight months, with an increased variance of discharge surpassing the variance of discharge following rainstorms. We conclude that Bayesian piecewise regression sheds new and unbiased insights on the duration, trend, and variance of streamflow response to strong earthquakes, and on how this response compares to that following rainstorms. KW - Bayesian analysis KW - Chile KW - discharge KW - earthquake KW - streamflow changes Y1 - 2021 U6 - https://doi.org/10.1029/2020WR028874 SN - 0043-1397 SN - 1944-7973 VL - 57 IS - 7 PB - Wiley CY - Hoboken, NJ ER - TY - JOUR A1 - Nievas, Cecilia A1 - Pilz, Marco A1 - Prehn, Karsten A1 - Schorlemmer, Danijel A1 - Weatherill, Graeme A1 - Cotton, Fabrice T1 - Calculating earthquake damage building by building BT - the case of the city of Cologne, Germany JF - Bulletin of earthquake engineering : official publication of the European Association for Earthquake Engineering N2 - The creation of building exposure models for seismic risk assessment is frequently challenging due to the lack of availability of detailed information on building structures. Different strategies have been developed in recent years to overcome this, including the use of census data, remote sensing imagery and volunteered graphic information (VGI). This paper presents the development of a building-by-building exposure model based exclusively on openly available datasets, including both VGI and census statistics, which are defined at different levels of spatial resolution and for different moments in time. The initial model stemming purely from building-level data is enriched with statistics aggregated at the neighbourhood and city level by means of a Monte Carlo simulation that enables the generation of full realisations of damage estimates when using the exposure model in the context of an earthquake scenario calculation. Though applicable to any other region of interest where analogous datasets are available, the workflow and approach followed are explained by focusing on the case of the German city of Cologne, for which a scenario earthquake is defined and the potential damage is calculated. The resulting exposure model and damage estimates are presented, and it is shown that the latter are broadly consistent with damage data from the 1978 Albstadt earthquake, notwithstanding the differences in the scenario. Through this real-world application we demonstrate the potential of VGI and open data to be used for exposure modelling for natural risk assessment, when combined with suitable knowledge on building fragility and accounting for the inherent uncertainties. KW - Building exposure modelling KW - Seismic damage assessment KW - Scenario KW - earthquake KW - Seismic risk KW - Cologne Y1 - 2022 U6 - https://doi.org/10.1007/s10518-021-01303-w SN - 1570-761X SN - 1573-1456 VL - 20 IS - 3 SP - 1519 EP - 1565 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Dahm, Torsten A1 - Cesca, Simone A1 - Hainzl, Sebastian A1 - Braun, Thomas A1 - Krüger, Frank T1 - Discrimination between induced, triggered, and natural earthquakes close to hydrocarbon reservoirs: A probabilistic approach based on the modeling of depletion-induced stress changes and seismological source parameters JF - Journal of geophysical research : Solid earth N2 - Earthquakes occurring close to hydrocarbon fields under production are often under critical view of being induced or triggered. However, clear and testable rules to discriminate the different events have rarely been developed and tested. The unresolved scientific problem may lead to lengthy public disputes with unpredictable impact on the local acceptance of the exploitation and field operations. We propose a quantitative approach to discriminate induced, triggered, and natural earthquakes, which is based on testable input parameters. Maxima of occurrence probabilities are compared for the cases under question, and a single probability of being triggered or induced is reported. The uncertainties of earthquake location and other input parameters are considered in terms of the integration over probability density functions. The probability that events have been human triggered/induced is derived from the modeling of Coulomb stress changes and a rate and state-dependent seismicity model. In our case a 3-D boundary element method has been adapted for the nuclei of strain approach to estimate the stress changes outside the reservoir, which are related to pore pressure changes in the field formation. The predicted rate of natural earthquakes is either derived from the background seismicity or, in case of rare events, from an estimate of the tectonic stress rate. Instrumentally derived seismological information on the event location, source mechanism, and the size of the rupture plane is of advantage for the method. If the rupture plane has been estimated, the discrimination between induced or only triggered events is theoretically possible if probability functions are convolved with a rupture fault filter. We apply the approach to three recent main shock events: (1) the M-w 4.3 Ekofisk 2001, North Sea, earthquake close to the Ekofisk oil field; (2) the M-w 4.4 Rotenburg 2004, Northern Germany, earthquake in the vicinity of the Sohlingen gas field; and (3) the M-w 6.1 Emilia 2012, Northern Italy, earthquake in the vicinity of a hydrocarbon reservoir. The three test cases cover the complete range of possible causes: clearly human induced, not even human triggered, and a third case in between both extremes. KW - induced seismicity KW - probabilistic discrimination KW - hydrocarbon field KW - triggered earthquake KW - seismic hazard KW - earthquake Y1 - 2015 U6 - https://doi.org/10.1002/2014JB011778 SN - 2169-9313 SN - 2169-9356 VL - 120 IS - 4 SP - 2491 EP - 2509 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Zhu, Chuanbin A1 - Pilz, Marco A1 - Cotton, Fabrice Pierre T1 - Evaluation of a novel application of earthquake HVSR in site-specific amplification estimation JF - Soil dynamics and earthquake engineering N2 - Ground response analyses (GRA) model the vertical propagations 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 fundamental frequency (f(0)), but HVSR values cannot be directly used to approximate the levels of S-wave amplifications. Motivated by the work of Kawase et al. (2019), we propose a procedure to correct earthquake HVSR amplitudes for direct amplification estimations. The empirical correction compensates HVSR by generic vertical amplification spectra categorized by the vertical fundamental frequency (f(0v)) via kappa-means clustering. In this investigation, we evaluate the effectiveness of the corrected HVSR in approximating observed linear amplifications in comparison with 1DSH modellings. We select a total of 90 KiK-net (Kiban Kyoshin network) surface-downhole sites which are found to have no velocity contrasts below their boreholes and thus of which surface-to-borehole spectral ratios (SBSRs) can be taken as their empirical transfer functions (ETFs). 1DSH-based theoretical transfer functions (TTFs) are computed in the linear domain considering uncertainties in Vs profiles through randomizations. 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 over frequencies from f(0) to 25 Hz. We find that the empirical correction to HVSR is highly effective and achieves a "good match" in both spectral shape and amplitude at the majority of the 90 KiK-net sites, as opposed to less than one-third for the 1DSH modelling. In addition, the empirical correction does not require a velocity model, which GRAs require, and thus has great potentials in seismic hazard assessments. KW - site amplification KW - HVSR KW - ground response analysis KW - KiK-net KW - earthquake Y1 - 2020 U6 - https://doi.org/10.1016/j.soildyn.2020.106301 SN - 0267-7261 SN - 1879-341X VL - 139 PB - Elsevier CY - Oxford 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 - Bricker, Jeremy D. A1 - Schwanghart, Wolfgang A1 - Adhikari, Basanta Raj A1 - Moriguchi, Shuji A1 - Roeber, Volker A1 - Giri, Sanjay T1 - Performance of Models for Flash Flood Warning and Hazard Assessment BT - the 2015 Kali Gandaki Landslide Dam Breach in Nepal JF - Mountain research and development N2 - The 2015 magnitude 7.8 Gorkha earthquake and its aftershocks weakened mountain slopes in Nepal. Co- and postseismic landsliding and the formation of landslide-dammed lakes along steeply dissected valleys were widespread, among them a landslide that dammed the Kali Gandaki River. Overtopping of the landslide dam resulted in a flash flood downstream, though casualties were prevented because of timely evacuation of low-lying areas. We hindcast the flood using the BREACH physically based dam-break model for upstream hydrograph generation, and compared the resulting maximum flow rate with those resulting from various empirical formulas and a simplified hydrograph based on published observations. Subsequent modeling of downstream flood propagation was compromised by a coarse-resolution digital elevation model with several artifacts. Thus, we used a digital-elevation-model preprocessing technique that combined carving and smoothing to derive topographic data. We then applied the 1-dimensional HEC-RAS model for downstream flood routing, and compared it to the 2-dimensional Delft-FLOW model. Simulations were validated using rectified frames of a video recorded by a resident during the flood in the village of Beni, allowing estimation of maximum flow depth and speed. Results show that hydrological smoothing is necessary when using coarse topographic data (such as SRTM or ASTER), as using raw topography underestimates flow depth and speed and overestimates flood wave arrival lag time. Results also show that the 2-dimensional model produces more accurate results than the 1-dimensional model but the 1-dimensional model generates a more conservative result and can be run in a much shorter time. Therefore, a 2-dimensional model is recommended for hazard assessment and planning, whereas a 1-dimensional model would facilitate real-time warning declaration. KW - Nepal KW - earthquake KW - landslide dam breach KW - flood KW - HEC-RAS KW - Delft-FLOW KW - steep mountain stream Y1 - 2017 U6 - https://doi.org/10.1659/MRD-JOURNAL-D-16-00043.1 SN - 0276-4741 SN - 1994-7151 VL - 37 IS - 1 SP - 5 EP - 15 PB - International Mountain Society CY - Lawrence ER - TY - JOUR A1 - Jara-Munoz, Julius A1 - Melnick, Daniel A1 - Zambrano, Patricio A1 - Rietbrock, Andreas A1 - Gonzalez, Javiera A1 - Argandona, Boris A1 - Strecker, Manfred T1 - Quantifying offshore fore-arc deformation and splay-fault slip using drowned Pleistocene shorelines, Arauco Bay, Chile JF - Journal of geophysical research : Solid earth N2 - Most of the deformation associated with the seismic cycle in subduction zones occurs offshore and has been therefore difficult to quantify with direct observations at millennial timescales. Here we study millennial deformation associated with an active splay-fault system in the Arauco Bay area off south central Chile. We describe hitherto unrecognized drowned shorelines using high-resolution multibeam bathymetry, geomorphic, sedimentologic, and paleontologic observations and quantify uplift rates using a Landscape Evolution Model. Along a margin-normal profile, uplift rates are 1.3m/ka near the edge of the continental shelf, 1.5m/ka at the emerged Santa Maria Island, -0.1m/ka at the center of the Arauco Bay, and 0.3m/ka in the mainland. The bathymetry images a complex pattern of folds and faults representing the surface expression of the crustal-scale Santa Maria splay-fault system. We modeled surface deformation using two different structural scenarios: deep-reaching normal faults and deep-reaching reverse faults with shallow extensional structures. Our preferred model comprises a blind reverse fault extending from 3km depth down to the plate interface at 16km that slips at a rate between 3.0 and 3.7m/ka. If all the splay-fault slip occurs during every great megathrust earthquake, with a recurrence of similar to 150-200years, the fault would slip similar to 0.5m per event, equivalent to a magnitude similar to 6.4 earthquake. However, if the splay-fault slips only with a megathrust earthquake every similar to 1000years, the fault would slip similar to 3.7m per event, equivalent to a magnitude similar to 7.5 earthquake. KW - splay fault KW - marine terraces KW - Arauco Bay KW - TerraceM KW - fore arc KW - earthquake Y1 - 2017 U6 - https://doi.org/10.1002/2016JB013339 SN - 2169-9313 SN - 2169-9356 VL - 122 SP - 4529 EP - 4558 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Mohr, Christian Heinrich A1 - Manga, Michael A1 - Wald, David T1 - Stronger peak ground motion, beyond the threshold to initiate a response, does not lead to larger stream discharge responses to earthquakes JF - Geophysical research letters N2 - The impressive number of stream gauges in Chile, combined with a suite of past and recent large earthquakes, makes Chile a unique natural laboratory to study several streams that recorded responses to multiple seismic events. We document changes in discharge in eight streams in Chile following two or more large earthquakes. In all cases, discharge increases. Changes in discharge occur for peak ground velocities greater than about 7-11cm/s. Above that threshold, the magnitude of both the increase in discharge and the total excess water do not increase with increasing peak ground velocities. While these observations are consistent with previous work in California, they conflict with lab experiments that show that the magnitude of permeability changes increases with increasing amplitude of ground motion. Instead, our study suggests that streamflow responses are binary. Plain Language Summary Earthquakes deform and shake the surface and the ground below. These changes may affect groundwater flows by increasing the permeability along newly formed cracks and/or clearing clogged pores. As a result, groundwater flow may substantially increase after earthquakes and remain elevated for several months. Here we document streamflow anomalies following multiple high magnitude earthquakes in multiple streams in one of the most earthquake prone regions worldwide, Chile. We take advantage of the dense monitoring network in Chile that recorded streamflow since the 1940s. We show that once a critical ground motion is exceeded, streamflow responses to earthquakes can be expected. KW - earthquake KW - streamflow KW - shaking KW - Chile KW - modeling Y1 - 2018 U6 - https://doi.org/10.1029/2018GL078621 SN - 0094-8276 SN - 1944-8007 VL - 45 IS - 13 SP - 6523 EP - 6531 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Tolorza, Violeta A1 - Mohr, Christian Heinrich A1 - Carretier, Sebastien A1 - Serey, Amador A1 - Sepulveda, Sergio A. A1 - Tapia, Joseline A1 - Pinto, Luisa T1 - Suspended sediments in chilean rivers reveal low postseismic erosion after the maule earthquake (Mw 8.8) during a severe drought JF - Journal of geophysical research : Earth surface N2 - We address the question of whether all large-magnitude earthquakes produce an erosion peak in the subaerial components of fluvial catchments. We evaluate the sediment flux response to the Maule earthquake in the Chilean Andes (Mw 8.8) using daily suspended sediment records from 31 river gauges. The catchments cover drainage areas of 350 to around 10,000 km(2), including a wide range of topographic slopes and vegetation cover of the Andean western flank. We compare the 3- to 8-year postseismic record of sediment flux to each of the following preseismic periods: (1) all preseismic data, (2) a 3-year period prior to the seismic event, and (3) the driest preseismic periods, as drought conditions prevailed in the postseismic period. Following the earthquake, no increases in suspended sediment flux were observed for moderate to high percentiles of the streamflow distribution (mean, median, and >= 75th percentile). However, more than half of the examined stations showed increased sediment flux during baseflow. By using a Random Forest approach, we evaluate the contributions of seismic intensities, peak ground accelerations, co-seismic landslides, hydroclimatic conditions, topography, lithology, and land cover to explain the observed changes in suspended sediment concentration and fluxes. We find that the best predictors are hillslope gradient, low-vegetation cover, and changes in streamflow discharge. This finding suggests a combined first-order control of topography, land cover, and hydrology on the catchment-wide erosion response. We infer a reduced sediment connectivity due to the postseismic drought, which increased the residence time of sediment detached and remobilized following the Maule earthquake. KW - earthquake KW - suspended sediment KW - Maule megathrust KW - Chile KW - catchment Y1 - 2019 U6 - https://doi.org/10.1029/2018JF004766 SN - 2169-9003 SN - 2169-9011 VL - 124 IS - 6 SP - 1378 EP - 1397 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Melnick, Daniel A1 - Moreno, Marcos A1 - Quinteros, Javier A1 - Carlos Baez, Juan A1 - Deng, Zhiguo A1 - Li, Shaoyang A1 - Oncken, Onno T1 - The super-interseismic phase of the megathrust earthquake cycle in Chile JF - Geophysical research letters N2 - Along a subduction zone, great megathrust earthquakes recur either after long seismic gaps lasting several decades to centuries or over much shorter periods lasting hours to a few years when cascading successions of earthquakes rupture nearby segments of the fault. We analyze a decade of continuous Global Positioning System observations along the South American continent to estimate changes in deformation rates between the 2010 Maule (M8.8) and 2015 Illapel (M8.3) Chilean earthquakes. We find that surface velocities increased after the 2010 earthquake, in response to continental-scale viscoelastic mantle relaxation and to regional-scale increased degree of interplate locking. We propose that increased locking occurs transiently during a super-interseismic phase in segments adjacent to a megathrust rupture, responding to bending of both plates caused by coseismic slip and subsequent afterslip. Enhanced strain rates during a super-interseismic phase may therefore bring a megathrust segment closer to failure and possibly triggered the 2015 event. KW - megathrust KW - earthquake KW - cycle KW - Chile Y1 - 2017 U6 - https://doi.org/10.1002/2016GL071845 SN - 0094-8276 SN - 1944-8007 VL - 44 IS - 2 SP - 784 EP - 791 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Gomez Zapata, Juan Camilo A1 - Zafrir, Raquel A1 - Pittore, Massimiliano A1 - Merino, Yvonne T1 - Towards a sensitivity analysis in seismic risk with probabilistic building exposure models BT - an application in Valparaiso, Chile using ancillary open-source data and parametric ground motions JF - ISPRS International Journal of Geo-Information N2 - Efforts have been made in the past to enhance building exposure models on a regional scale with increasing spatial resolutions by integrating different data sources. This work follows a similar path and focuses on the downscaling of the existing SARA exposure model that was proposed for the residential building stock of the communes of Valparaiso and Vina del Mar (Chile). Although this model allowed great progress in harmonising building classes and characterising their differential physical vulnerabilities, it is now outdated, and in any case, it is spatially aggregated over large administrative units. Hence, to more accurately consider the impact of future earthquakes on these cities, it is necessary to employ more reliable exposure models. For such a purpose, we propose updating this existing model through a Bayesian approach by integrating ancillary data that has been made increasingly available from Volunteering Geo-Information (VGI) activities. Its spatial representation is also optimised in higher resolution aggregation units that avoid the inconvenience of having incomplete building-by-building footprints. A worst-case earthquake scenario is presented to calculate direct economic losses and highlight the degree of uncertainty imposed by exposure models in comparison with other parameters used to generate the seismic ground motions within a sensitivity analysis. This example study shows the great potential of using increasingly available VGI to update worldwide building exposure models as well as its importance in scenario-based seismic risk assessment. KW - exposure KW - buildings KW - Bayesian model KW - downscaling KW - OpenStreetMap KW - ground motion fields KW - sensitivity KW - earthquake KW - vulnerability KW - risk Y1 - 2022 U6 - https://doi.org/10.3390/ijgi11020113 SN - 2220-9964 VL - 11 IS - 2 PB - MDPI CY - Basel ER -