Seismic Hazard Assessment Research Articles

Multipath Transfer-Function Correction Method to Predict Site-Specific Amplification at City Scale

Abstract The site-specific amplification of seismic waves is an essential component of local seismic hazard assessment. It can be evaluated from empirical data, but measurements are feasible just in a limited number of locations. Hence, at the city scale, there is a need for the theoretical prediction and interpolation of the amplification. In this article, we introduce a physics-based method to predict the site-specific amplification and duration in a broad frequency range. The method is based on a novel energy-based concept of the multipath propagation of waves in viscoelastic media with random heterogeneities. The amplification is expressed by the surface-outcrop transfer function of the multipath wave propagation, which is defined by expected values of the energy spectral ratio. The method is applied to the near-surface 2D velocity model in the city of Zürich in Switzerland. The predicted amplification is validated by empirical data at a nearby seismic station, and it is compared with the soil class and other site-condition proxies. Finally, the method performance is demonstrated by the prediction of site-specific seismic waveforms and response spectra for the 2022 ML 4.7 Mulhouse earthquake.

Geofluids as a possible unconventional tool for seismic hazard assessment

In recent decades, phenomenological methods known as Recognition of Earthquake-Prone Areas (REPA) were set up for identifying potential sites of powerful earthquakes. The information on potential earthquake sources provided by the REPA method is an essential part of seismic hazard assessment methodology. For the first time, we have combined global-scale information on the geographic occurrence of geofluids with global-scale information on earthquake occurrence, heat flow distribution, and S-wave dispersion, to gain insights into the evolution of local stress-strain fields. We focused on areas characterized by the occurrence of thermal waters and/or by the release of deep-seated gases, as traced by the isotope composition of associated helium. We noticed that the geographic distribution of these geofluids could serve as an indirect indicator of crustal permeability anomalies generated by crustal deformation procedures. This study proposes adding geofluids to the list of fundamental geological parameters to be considered in hazard assessment research.

Induced Seismicity Hazard Assessment for a Potential CO2 Storage Site in the Southern San Joaquin Basin, CA

California’s Central Valley offers vast opportunities for CO2 storage in deep saline aquifers. We conducted an induced seismicity hazard assessment for a potential injection site in the southern San Joaquin Basin for 18 years of injection at 0.68 MtCO2/yr and 100 years of monitoring. We mapped stress, faults, and seismicity in a 30 km radius around the site to build a geomechanical model and resolve the stresses on major faults. From a 3D hydromechanical simulation of the CO2 plume, we calculated the change in pressure over time on these faults and determined the conditions for safe injection. Lacking any subsurface imaging, we also conducted a probabilistic fault slip analysis using numerous random distributions of faults and a range of geomechanical parameters. Our results show that the change in probability of fault slip can be minimized by controlling the size, migration, and magnitude of the pressure plume. We also constructed a seismic catalog for the last 20 years around the site and characterized the natural patterns of seismicity. We use these results to establish criteria for evaluating potential-induced events during the storage period and to develop a traffic light response system. This study represents a first-order procedure to evaluate the seismic hazards presented by CO2 storage and incorporate uncertainties in hydrological and geomechanical parameters.

Impact of Variable Fault Geometries and Slip Rates on Earthquake Catalogs From Physics‐Based Simulations of a Normal Fault

AbstractPhysics‐based earthquake simulators have been developed to overcome the relatively short duration and incompleteness of historical earthquake and paleoseismic records, respectively. These simulators have the potential to be a useful addition to seismic hazard assessment as they produce millions of synthetic earthquakes over thousands to millions of years using predefined fault geometries and slip rates. Due to the sparsity of fault data and the computational expense of the modeling, it is common to simplify earthquake simulator input parameters. Fault surfaces are typically characterized by simplified mapped traces and constant dip with depth, with slip rates that are often assumed to be uniform over the fault plane. This study uses the well‐defined 3D geometry of an active normal fault in offshore Aotearoa New Zealand, the Cape Egmont Fault, to demonstrate the impact of using nonuniform slip rates and nonplanar fault geometries on the resulting synthetic earthquakes from the earthquake simulator RSQSim. Adopting variable slip rates that decrease to zero along the fault tipline (rather than uniform slip rates) reduces unrealistically high nucleation rates of seismicity along fault edges. Introduction of complex 3D fault geometries, including fault segmentation and bends on kilometer scales, and variable slip rates produces less characteristic earthquake populations, increasing the number of M6‐7 moderate‐large magnitude events. Incorporation of variable fault geometries and slip rates in physics‐based simulators may modify the seismic hazards estimated from synthetic earthquake catalogs.

Comprehensive seismic hazard assessment for Guwahati City, Northeast India: Insights from probabilistic and deterministic seismic hazard analysis

This paper presents a comprehensive seismic hazard assessment for Guwahati city, located in the northeast region of India. The earthquake data considered for the study is from 1762 to 2020, which was sourced from the published data of various seismological agencies. The fault information comprises of the latest studies and Seismotectonic Atlas (SEISAT) data. The density of earthquakes close to the faults was used to define the fault zones. The G-R relationship was utilized to calculate the seismicity parameters of the identified faults. We have used PSHA and DSHA to estimate the ground motion parameters such as peak ground acceleration and spectral acceleration at various probabilities of exceedance to calculate the level of seismic hazard. The results indicate that the seismic hazard in Guwahati is moderate to high, with several active faults in the vicinity and a high potential for strong ground motions. This study includes identifying the controlling source for Guwahati and plotting the seismic hazard curve and uniform hazard spectra for various probabilities of exceedance, which will give a basic idea of the seismic hazard of the city. The findings of this study can be used as a basis for earthquake risk reduction and mitigation strategies in Guwahati.

Unravelling Karachi’s Seismic Potential: Estimating Maximum Ground Shaking in Various Zones

Karachi, a sprawling city spanning over 3500[Formula: see text]sq. km, exhibits significant variability in seismic hazard across its expanse. This study employs a deterministic approach for seismic hazard assessment due to the unavailability of a long-term seismic archive required for a probabilistic approach, given the city’s relatively young age. Furthermore, a novel methodology is employed in this study, utilizing all known faults within Karachi’s seismic vicinity for conducting Deterministic Seismic Hazard Assessment (DSHA). Individual hazards associated with each seismic source are estimated, enabling the determination of the most severe hazard for the development of a seismic zoning map. The resulting DSHA-based seismic hazard assessment categorizes Karachi into four seismic zones, ranging from Zone 2A to Zone 4. This paper concludes that for a vast city like Karachi, relying solely on a single fault source for DSHA does not accurately represent the realistic seismic hazard to the region.

Seismic Hazard Assessment and Source Zone Delineation in Northeast India: A Case Study of the Kopili Fault Region and Its Vicinity

Seismic Hazard Assessment and Source Zone Delineation in Northeast India: A Case Study of the Kopili Fault Region and Its Vicinity

Slip localization on multiple fault splays accommodating distributed deformation across normal fault complexities

Deformation across structural complexities such as along-strike fault bends may be accommodated by distributed faulting, with multiple fault splays working to transfer the deformation between two principal fault segments. In these contexts, an unsolved question is whether fault activity is equally distributed through time, with multiple fault splays recording the same earthquakes, or it is instead localized in time and space across the distributed faults, with earthquakes being clustered on specific fault splays. To answer this question, we studied the distributed deformation across a structural complexity of the Mt. Marine fault (Central Apennines, Italy), where multiple fault splays accommodate the deformation throughout the change in strike of the fault. Our multidisciplinary (remote sensing analysis, geomorphological-geological mapping, geophysical and paleoseismological surveys) study identified five principal synthetic and antithetic fault splays arranged over an across-strike distance of 500 m, all of which showing evidence of multiple surface-rupturing events during the Late Pleistocene-Holocene. The fault splays exhibit different and variable activity rates, suggesting that fault activity is localized on specific fault splays through space and time. Nonetheless, our results suggest that multiple fault splays can rupture simultaneously during large earthquakes. Our findings have strong implications on fault-based seismic hazard assessments, as they imply that data collected on one splay may not be representative of the behaviour of the entire fault. This can potentially bias seismic hazard calculations.

A multi-scenario based micro seismic hazard assessment of the Bhuj City, western India incorporating geophysical and geotechnical parameters

The micro-seismic hazard assessment (micro-SHA) of the Bhuj city (highest seismic zone V) has been accomplished considering seismotectonic as well as shallow subsurface modeling through geophysical (multi-channel analysis of surface waves (MASW) survey at 19 sites) and geotechnical parameters from 28 boreholes distributed in the entire Bhuj city. The average shear wave velocity through the MASW survey at 30 m depth (VS30) is estimated in the range of 400–915 m/s (NEHRP C-type and B-type soil classes). Seismotectonically justified a total of 54 scenario-earthquakes (SEQs) along all major faults have been considered to evaluate the strong ground motion at generic soil level having a shear wave velocity of 760 m/s and depth of 12–28 m. The surface level strong motion (SM) has been estimated through ground response analysis preparing soil models along all boreholes. The PGA at the surface in Bhuj city has been estimated in the range of 528 cm/s2 to 1020 cm/s2; highest in the central-western part of the Bhuj city where clay with high plasticity is present. The mean-spectral acceleration over the study area for 0.2 s (corresponding to 1-2 story), 0.55 s (4-5 story), 1sec (high rise) and 1.25 s period (large structures) are prepared at the surface from all scenario earthquakes. The amplification of SM in the Bhuj city is computed in the range of 1.7–3.7.

Fault Source Models Show Slip Rates Measured across the Width of the Entire Fault Zone Best Represent the Observed Seismicity of the Pallatanga–Puna Fault, Ecuador

AbstractWe explore how variation of slip rates in fault source models affect computed earthquake rates of the Pallatanga–Puna fault system in Ecuador. Determining which slip rates best represent fault-zone seismicity is vital for use in probabilistic seismic hazard assessment (PSHA). However, given the variable spatial and temporal scales slip rates are measured over, significantly different rates can be observed along the same fault. The Pallatanga–Puna fault in southern Ecuador exemplifies a fault where different slip rates have been measured using methods spanning different spatial and temporal scales, and in which historical data and paleoseismic studies provide a record of large earthquakes over a relatively long time span. We use fault source models to calculate earthquake rates using different slip rates and geometries for the Pallatanga–Puna fault, and compare the computed magnitude–frequency distributions (MFDs) to earthquake catalog MFDs from the fault zone. We show that slip rates measured across the entire width of the fault zone, either based on geodesy or long-term geomorphic offsets, produce computed MFDs that compare more favorably with the catalog data. Moreover, we show that the computed MFDs fit the earthquake catalog data best when they follow a hybrid-characteristic MFD shape. These results support hypotheses that slip rates derived from a single fault strand of a fault system do not represent seismicity produced by the entire fault zone.

Special Issue on Comprehensive Research in Earthquake Forecasting and Seismic Hazard Assessment

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Hypsometric Analysis and Tectonic Activity Evaluation in the Semangko Fault Zone: A Literature Review

This comprehensive review synthesizes and analyzes current literature on hypsometric analysis and its application in evaluating tectonic activity within the Semangko Fault Zone, a critical segment of the Sumatran Fault system. The study examines how hypsometric curves (HC) and hypsometric integrals (HI) serve as quantitative indicators of landscape evolution and tectonic deformation. By critically analyzing existing research, this review highlights the strong correlation between high HI values and areas of active tectonic uplift within the fault zone. The paper also explores the integration of hypsometric analysis with other geomorphic indices and its potential in seismic hazard assessment. Our findings underscore the significance of hypsometric analysis as a valuable tool in understanding the complex tectonic processes shaping the Semangko Fault Zone and its implications for regional seismic risk evaluation and land-use planning.

Earthquake disaster database system in assessment and prediction of seismic hazard

Earthquake disaster database system in assessment and prediction of seismic hazard

Connection between Variations of the Probability Distribution of the Recurrence Time and Phases of the Seismic Activity.

The probability distribution of the interevent time between two successive earthquakes has been the subject of numerous studies for its key role in seismic hazard assessment. In recent decades, many distributions have been considered, and there has been a long debate about the possible universality of the shape of this distribution when the interevent times are properly rescaled. In this work, we aim to discover if there is a link between the different phases of a seismic cycle and the variations in the distribution that best fits the interevent times. To do this, we consider the seismic activity related to the Mw 6.1 L'Aquila earthquake that occurred on 6 April 2009 in central Italy by analyzing the sequence of events recorded from April 2005 to July 2009, and then the seismic activity linked to the sequence of the Amatrice-Norcia earthquakes of Mw 6 and 6.5, respectively, and recorded in the period from January 2009 to June 2018. We take into account some of the most studied distributions in the literature: q-exponential, q-generalized gamma, gamma and exponential distributions and, according to the Bayesian paradigm, we compare the value of their posterior marginal likelihood in shifting time windows with a fixed number of data. The results suggest that the distribution providing the best performance changes over time and its variations may be associated with different phases of the seismic crisis.

High-Resolution Shallow Structure along the Anninghe Fault Zone, Sichuan, China, Constrained by Active Source Tomography

Abstract The Anninghe fault (ANHF), located in southwest China, was a major block boundary that hosted M 7.5 earthquakes historically. For seismic hazard assessment, it is critical to investigate fault properties before future earthquakes. To investigate the fault structure, we deployed three linear dense arrays with an aperture of ∼8–9 km across different segments of the ANHF from October 2019 to March 2020. More importantly, we detonated a new methane source to generate seismic waves, which is environmentally friendly and can be used in different regions such as mountainous and urban areas. After data acquisition, we first removed the noise to accurately pick up the first arrivals of seismic waves. Then, we conducted the first-arrival seismic tomography, a method commonly used in the petroleum industry, to obtain the high-resolution P-wave velocity structure. The tomographic results showed distinct low-velocity zones (LVZs) of ∼1000–1500 m in width and ∼300–400 m in depth along the fault, well consistent with the lateral distribution of site amplification that was derived from regional earthquake waveforms. These LVZs may have formed as a combined result of the fault damage zone and ANHF-controlled sediments. As the Anning River Valley is densely populated, our newly identified LVZs shed lights on earthquake hazard in the region. In addition, we demonstrate that using a combination of methane detonation sources, linear dense arrays, and active source tomography can effectively determine the shallow P-wave velocity model in complex environments (i.e., mountains and urban areas).

Seismic hazard assessment studies based on developed deterministic and probabilistic approaches for the central-east of Iran region

PurposeThis Study aims to present the seismic hazard assessment of the earthquake-prone eastern of Iran that has become more important due to its growing economic importance. Many cities in this region have experienced life and financial losses due to major earthquakes in recent years. Thus, in this study the seismic hazard maps and curves, and site-specific spectrums were obtained by using probabilistic approaches for the region.Design/methodology/approachThe seismotectonic information, seismicity data and earthquake catalogues were gathered, main active seismic sources were identified and seismic zones were considered to cover the potential active seismic regions. The seismic model based on logic tree method used two seismic source models, two declustered catalogues, three choices for earthquake recurrence parameters and maximum considered earthquakes and four ground motion predicting (attenuation) models (GMPE).FindingsThe results showed a wide range of seismic hazards levels in the study region. The peak ground acceleration (PGAs) for 475 years returns period ranges between 0.1 g in the north-west part of the region with low seismic activity, to 0.52 g in the south-west part with high levels of seismicity. The PGAs for a 2,475-year period, also ranged from 0.12 to 0.80 g for the same regions. The computed hazard results were compared to the acceptable level of seismic hazard in the region based on Iran seismic code.Originality/valueA new probabilistic approach has been developed for obtaining seismic hazard maps and curves; these results would help engineers in design of earthquake-resistant structures.

Characterizing High Rate GNSS Velocity Noise for Synthesizing a GNSS Strong Motion Learning Catalog

Data-driven approaches to identify geophysical signals have proven beneficial in high dimensional environments where model-driven methods fall short. GNSS offers a source of unsaturated ground motion observations that are the data currency of ground motion forecasting and rapid seismic hazard assessment and alerting. However, these GNSS-sourced signals are superposed onto hardware-, location- and time-dependent noise signatures influenced by the Earth’s atmosphere, low-cost or spaceborne oscillators, and complex radio frequency environments. Eschewing heuristic or physics based models for a data-driven approach in this context is a step forward in autonomous signal discrimination. However, the performance of a data-driven approach depends upon substantial representative samples with accurate classifications, and more complex algorithm architectures for deeper scientific insights compound this need. The existing catalogs of high-rate (≥1Hz) GNSS ground motions are relatively limited. In this work, we model and evaluate the probabilistic noise of GNSS velocity measurements over a hemispheric network. We generate stochastic noise time series to augment transferred low-noise strong motion signals from within 70 kilometers of strong events (≥ MW 5.0) from an existing inertial catalog. We leverage known signal and noise information to assess feature extraction strategies and quantify augmentation benefits. We find a classifier model trained on this expanded pseudo-synthetic catalog improves generalization compared to a model trained solely on a real-GNSS velocity catalog, and offers a framework for future enhanced data driven approaches.

Structure and kinematics of active faulting in the northern domain of Western and Central Alborz, Iran and interpretation in terms of tectonic evolution of the region

Field evidence, seismicity, and geodetic data are combined to define the tectonic evolution along the northern domain of the Western and Central Alborz ranges, which have experienced significant earthquakes. One of our main focuses is to present the geometric-kinematic characteristics of active fault planes in the North Alborz fault zone and its subsidiary faults as a basis for seismic hazard assessment. To evaluate the seismotectonics in the region, three active segments of the seismic zone are identified. These segments primarily exhibit reverse mechanisms and left-lateral strike-slip components and act as the boundaries of neotectonic stress domains around the transition zone between Alborz and the South Caspian Basin. The spatial distribution of the strike-slip and dip-slip faulting over the Western and Central Alborz range supports our understanding of the geodynamic processes of the region. Our map of local active faults reveals five main systems with N–S, NE–SW, ENE–WSW, E–W, and NW–SE directions. Field studies indicate that strike-slip movements predominate and are consistent with a ∼WNW-ESE-oriented left-lateral wrench system. Pure left-lateral strike-slip faults trending E-W, extensional faults trending NE–SW, and compressional faults trending NW-SE are identified. Regional field investigations reveal spatial variations in the fault zone width of the northern domain of the Western and Central Alborz. The findings demonstrate that fault zone structures and their spatial distribution along the width of the area are strongly affected by the strain partitioning process in the transpressional zone. A spectacular well-exposed transpressional zone from the Western and Central Alborz region is described in detail, where outer domains are faults with a dominant reverse mechanism, and the inner domain is a wrench zone that includes faults with a dominant strike-slip mechanism. The seismic activity in the Northern Alborz region is mainly concentrated along the North Alborz fault zone and its subsidiary fault planes, of which some are identified for the first time in this research. Significant seismic events have occurred at locations where these newly identified fault planes interact. The maximum values of the geodetic strain axes in Western and Central Alborz are consistent with the area of high seismicity.

A review of soil liquefaction in the Caribbean Greater and Lesser Antilles in reconsidering the ground motion effect of the M7.0 2010 Haiti earthquake in the Port-au-Prince Seaport and Léogâne Plain

On 12 January 2010, the M7.0 Haiti earthquake caused infrastructure damage induced by extensive soil liquefaction and foundation failure in the Port-au-Prince International Seaport and Léogâne Plain. This study re-examines the soil liquefaction effects of the main shock and aftershock events by exploring the existing studies on calcareous sands, reviewing the phenomenon of liquefaction in the Caribbean Islands, and associating them within the seismic history of the Greater and Lesser Antilles. Due to the geomorphology of the Islands, urban development has typically been concentrated along the coast, in locations vulnerable to soil liquefaction. This study demonstrates that the liquefaction that occurred at sites in the M7.0 Haiti event was triggered by the main shock even at low peak ground accelerations (PGAs), the first aftershock effects were significant, and soil liquefaction was not rare in the Antilles. It identifies the elements that characterize historical cases of soil liquefaction caused by earthquakes in the Caribbean Islands. In addition, it points out the characteristics and findings of paleoliquefaction and paleoseismicity investigations conducted in the Caribbean region. Investigations and studies on the calcareous sand liquefaction and paleoseismology are essential to improve the seismic hazard and risk assessment of the Caribbean Islands. The existence of a large number of studies making reference to this topic highlights its significance.

Seismotectonics of sources of strong earthquakes in the Caucasus: Results of studies by Evgeny Alexandrovich Rogozhin

The results of a consistent and versatile study of the seismotectonics of source zones of strong modern earthquakes in the Caucasus under the guidance and with the participation of E.A. Rogozhin. The sources of all strong modern earthquakes have been studied from a unified methodological standpoint. The collected data on the tectonic position of seismic sources make it possible to draw certain conclusions that are of practical interest in order to seismic hazard assessment.