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1.
Sensors (Basel) ; 24(13)2024 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-39001031

RESUMO

Moho tomography is important for studying the deep Earth structure and geodynamics, and fiber borehole strainmeters are broadband, low-noise, and attractive tools for seismic observation. Recently, many studies have shown that fiber optic seismic sensors can be used for subsurface structure imaging based on ambient noise cross-correlation, similar to conventional geophones. However, this array-dependent cross-correlation method is not suitable for fiber borehole strainmeters. Here, we developed a Moho imaging scheme for the characteristics of fiber borehole strainmeters based on ambient noise autocorrelation. S-wave reflection signals were extracted from the ambient noise through a series of processing steps, including phase autocorrelation (PAC), phase-weighted stacking (PWS), etc. Subsequently, the time-to-depth conversion crustal thickness beneath the station was calculated. We applied our scheme to continuous four-component recordings from four fiber borehole strainmeters in Lu'an, Anhui Province, China. The obtained Moho depth was consistent with the previous research results. Our work shows that this method is suitable for Moho imaging with fiber borehole strainmeters without relying on the number of stations.

2.
Proc Natl Acad Sci U S A ; 121(25): e2401440121, 2024 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-38875145

RESUMO

At fast-spreading centers, faults develop within the axial summit trough (AST; 0 to 250 m around the axis) primarily by diking-induced deformation originating from the axial magma lens (AML). The formation of the prominent abyssal-hill-bounding faults beyond the axial high (>2,000 m) is typically associated with the unbending of the lithosphere as it cools and spreads away from the AST. The presence of faults is rarely mapped between these two thermally distinct zones, where the lithosphere is still too hot for the faults to be linked with the process of thermal cooling and outside of the AST where the accretional diking process dominates the ridge axis. Here, we reveal a remarkable vertical alignment between the distinct morphological features of the magma body and the orientation of these faults, by comparison of 3-D seismic imagery and bathymetry data collected at the East Pacific Rise (EPR) 9°50'N. The spatial coincidence and asymmetric nucleation mode of the mapped faults represent the most direct evidence for magmatically induced faulting near the ridge axis, providing pathways for hydrothermalism and magma emplacement, helping to build the crust outside of the AST. The high-resolution seafloor and subsurface images also enable revised tectonic strain estimates, which shows that the near-axis tectonic component of seafloor spreading at the EPR is an order of magnitude smaller than previously thought with close to negligible contribution of lava buried faults to spreading.

3.
Heliyon ; 10(11): e31719, 2024 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-38841443

RESUMO

High-permeability sand cannot control the water that is stored behind an embankment. In addition, if clay cannot be provided within a reasonable distance of the embankment construction site, an alternative method must be found. The study proposes using a polyurethane foam-sand mixture to construct an impermeable embankment. The main purpose of the paper was to predict the seismic stability of the embankment. The nonlinear finite element models (FEMs) are applied along with artificial neural networks (ANNs), and this research method applied was performed to investigate the main objectives of the research. Catastrophe theory was used to predict the mechanism of differential displacement in the Y direction at selected points of the embankment model. For model smooth functions, the basis spline (B-spline) method was applied to simulate the catastrophe progression index value. Results revealed that the suitability of the polyurethane foam-sand mixture controls the acceleration, displacement, strain, and stress of the model at points selected in different parts of the embankment. Moreover, it was found that the deformation pattern of the model was related to the polyurethane foam-sand mixture ratios. Furthermore, the main contribution was that the seismic response of the embankment model could be improved with the right percentage of polyurethane foam added to the sand. Results were validated by referencing those available in the literature.

4.
Philos Trans A Math Phys Eng Sci ; 382(2275): 20230185, 2024 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-38910394

RESUMO

The largest magnitude earthquake in a sequence is often used as a proxy for hazard estimates, as consequences are often predominately from this single event (in small seismic zones). In this article, the concept of order statistics is adapted to infer the maximum magnitude ([Formula: see text]) of an earthquake catalogue. A suite tools developed here can discern [Formula: see text] influences through hypothesis testing, quantify [Formula: see text] through maximum likelihood estimation (MLE) or select the best [Formula: see text] prediction amongst several models. The efficacy of these tools is benchmarked against synthetic and real-data tests, demonstrating their utility. Ultimately, 13 cases of induced seismicity spanning wastewater disposal, hydraulic fracturing and enhanced geothermal systems are tested for volume-based [Formula: see text]. I find that there is no evidence of volume-based processes influencing any of these cases. On the contrary, all these cases are adequately explained by an unbounded magnitude distribution. This is significant because it suggests that induced earthquake hazards should also be treated as unbounded. On the other hand, if bounded cases exist, then the tools developed here will be able to discern them, potentially changing how an operator mitigates these hazards. Overall, this suite of tools will be important for better-understanding earthquakes and managing their risks. This article is part of the theme issue 'Induced seismicity in coupled subsurface systems'.

5.
Fundam Res ; 4(3): 603-610, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-38933194

RESUMO

A magnetorheological self-centering brace (MR-SCB) has been proposed to improve the energy dissipation capability of the brace. In this paper, a 15-story MR-SCB braced frame is numerically analyzed to examine its seismic performance and resilience. The MR-SCB provides higher lateral stiffness than the buckling restrained brace and greater energy dissipation capability than the existing self-centering brace. The brace also exhibits a reliable recentering capacity. Under rare earthquakes, the maximum average residual deformation ratio of the structure is less than the 0.5% limit. Under mega earthquakes, the maximum average interstory drift ratio of the structure does not exceed the 2.0% elastoplastic limit, and its maximum average floor acceleration ratio is 1.57. The effects of mainshock and aftershock on the structural behavior are also investigated. The interstory drift and residual deformation of the structure increase with the increase of the intensity of the aftershock. Under aftershocks with the same intensity as the mainshocks, the maximum increment of the residual deformation ratio of the structure is 81.8%, and the average interstory drift ratios of the 12th, 7th, and 3rd stories of the structure are increased by 13.4%, 9.2% and 7.5%, respectively. The strong aftershock may significantly cause increased damage to the structure, and increase its collapse risk and residual deformation.

6.
Sci Rep ; 14(1): 14678, 2024 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-38918401

RESUMO

Earthquake prevention and disaster mitigation are crucial aspects of social welfare that significantly impact national public security. This paper presents a seismic risk assessment and hazard prediction of the Hunhe Fault in the Shengyang-Fushun (Shen-Fu) New District. The target area is at risk of seismic damage due to two major branch ruptures, namely, F9 and F1; these ruptures have the potential to generate maximum earthquakes with a magnitude of 6.0 in the next 50 to 100 years. A three-dimensional underground velocity structure and asperity source model were established for the target faults. Subsequently, a hybrid technique combining deterministic and empirical approaches was employed to simulate the broadband strong ground motion of the target region in anticipation of the occurrence of expected scenario earthquakes. The distributions of peak ground acceleration (PGA), peak ground velocity (PGV) and peak ground displacement (PGD) for the area are provided, and the results indicate that densely populated urban areas could experience PGA values close to 280 cm/s2 along the fault traces. This study provides a reliable basis for engineering construction and urban planning in the Shen-Fu New District.

7.
Entropy (Basel) ; 26(6)2024 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-38920473

RESUMO

Bridges may undergo structural vibration responses when exposed to seismic waves. An analysis of structural vibration characteristics is essential for evaluating the safety and stability of a bridge. In this paper, a signal time-frequency feature extraction method (NTFT-ESVD) integrating standard time-frequency transformation, singular value decomposition, and information entropy is proposed to analyze the vibration characteristics of structures under seismic excitation. First, the experiment simulates the response signal of the structure when exposed to seismic waves. The results of the time-frequency analysis indicate a maximum relative error of only 1% in frequency detection, and the maximum relative errors in amplitude and time parameters are 5.9% and 6%, respectively. These simulation results demonstrate the reliability of the NTFT-ESVD method in extracting the time-frequency characteristics of the signal and its suitability for analyzing the seismic response of the structure. Then, a real seismic wave event of the Su-Tong Yangtze River Bridge during the Hengchun earthquake in Taiwan (2006) is analyzed. The results show that the seismic waves only have a short-term impact on the bridge, with the maximum amplitude of the vibration response no greater than 1 cm, and the maximum vibration frequency no greater than 0.2 Hz in the three-dimensional direction, indicating that the earthquake in Hengchun will not have any serious impact on the stability and security of the Su-Tong Yangtze River Bridge. Additionally, the reliability of determining the arrival time of seismic waves by extracting the time-frequency information from structural vibration response signals is validated by comparing it with results from seismic stations (SSE/WHN/QZN) at similar epicenter distances published by the USGS. The results of the case study show that the combination of dynamic GNSS monitoring technology and time-frequency analysis can be used to analyze the impact of seismic waves on the bridge, which is of great help to the manager in assessing structural seismic damage.

8.
Philos Trans A Math Phys Eng Sci ; 382(2276): 20230184, 2024 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-38945164

RESUMO

There is an ongoing discussion about how to forecast the maximum magnitudes of induced earthquakes based on operational parameters, subsurface conditions and physical process understanding. Although the occurrence of damage caused by induced earthquakes is rare, some cases have caused significant economic loss, injuries and even loss of life. We analysed a global compilation of earthquakes induced by hydraulic fracturing, geothermal reservoir stimulation, water disposal, gas storage and reservoir impoundment. Our analysis showed that maximum magnitudes scale with the characteristic length of pressure diffusion in the brittle Earth's crust. We observed an increase in the nucleation potential of larger-magnitude earthquakes with time and explained it by diffusion-controlled growth of the pressure-perturbed part of faults. Numerical and analytical fault size modelling supported our findings. Finally, we derived magnitude scaling laws to manage induced seismic hazard of upcoming energy projects prior to operation. This article is part of the theme issue 'Induced seismicity in coupled subsurface systems'.

9.
Sci Rep ; 14(1): 12667, 2024 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-38831094

RESUMO

The glutenite reservoir in an exploration area in eastern China is well-developed and holds significant exploration potential as an important oil and gas alternative layer. However, due to the influence of sedimentary characteristics, the glutenite reservoir exhibits strong lateral heterogeneity, significant vertical thickness variations, and low accuracy in reservoir space characterization, which affects the reasonable and effective deployment of development wells. Seismic data contains the three-dimensional spatial characteristics of geological bodies, but how to design a suitable transfer function to extract the nonlinear relationship between seismic data and reservoirs is crucial. At present, the transfer functions are concentrated in low-dimensional or high-dimensional fixed mathematical models, which cannot accurately describe the nonlinear relationship between seismic data and complex reservoirs, resulting in low spatial description accuracy of complex reservoirs. In this regard, this paper first utilizes a fusion method based on probability kernel to fuse seismic attributes such as wave impedance, effective bandwidth, and composite envelope difference. This provide a more intuitive reflection of the distribution characteristics of glutenite reservoirs. Moreover, a hybrid nonlinear transfer function is established to transform the fused attribute cube into an opaque attribute cube. Finally, the illumination model and ray casting method are used to perform voxel imaging of the glutenite reservoirs, brighten the detailed characteristics of reservoir space, and then form a set of methods for ' brightening reservoirs and darkening non-reservoirs ', which improves the spatial engraving accuracy of glutenite reservoirs.

10.
Sensors (Basel) ; 24(11)2024 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-38894265

RESUMO

This paper introduces SEISMONOISY, an application designed for monitoring the spatiotemporal characteristic and variability of the seismic noise of an entire seismic network with a quasi-real-time monitoring approach. Actually, we have applied the developed system to monitor 12 seismic networks distributed throughout the Italian territory. These networks include the Rete Sismica Nazionale (RSN) as well as other regional networks with smaller coverage areas. Our noise monitoring system uses the methods of Spectral Power Density (PSD) and Probability Density Function (PDF) applied to 12 h long seismic traces in a 24 h cycle for each station, enabling the extrapolation of noise characteristics at seismic stations after a Seismic Noise Level Index (SNLI), which takes into account the global seismic noise model, is derived. The SNLI value can be used for different applications, including network performance evaluation, the identification of operational problems, site selection for new installations, and for scientific research applications (e.g., volcano monitoring, identification of active seismic sequences, etc.). Additionally, it aids in studying the main noise sources across different frequency bands and changes in the characteristics of background seismic noise over time.

11.
Sensors (Basel) ; 24(11)2024 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-38894445

RESUMO

The detection of seismic activity precursors as part of an alarm system will provide opportunities for minimization of the social and economic impact caused by earthquakes. It has long been envisaged, and a growing body of empirical evidence suggests that the Earth's electromagnetic field could contain precursors to seismic events. The ability to capture and monitor electromagnetic field activity has increased in the past years as more sensors and methodologies emerge. Missions such as Swarm have enabled researchers to access near-continuous observations of electromagnetic activity at second intervals, allowing for more detailed studies on weather and earthquakes. In this paper, we present an approach designed to detect anomalies in electromagnetic field data from Swarm satellites. This works towards developing a continuous and effective monitoring system of seismic activities based on SWARM measurements. We develop an enhanced form of a probabilistic model based on the Martingale theories that allow for testing the null hypothesis to indicate abnormal changes in electromagnetic field activity. We evaluate this enhanced approach in two experiments. Firstly, we perform a quantitative comparison on well-understood and popular benchmark datasets alongside the conventional approach. We find that the enhanced version produces more accurate anomaly detection overall. Secondly, we use three case studies of seismic activity (namely, earthquakes in Mexico, Greece, and Croatia) to assess our approach and the results show that our method can detect anomalous phenomena in the electromagnetic data.

12.
Sensors (Basel) ; 24(10)2024 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-38793898

RESUMO

A 3D vertical seismic profiling (VSP) survey was acquired using a distributed acoustic sensing (DAS) system in the Permian Basin, West Texas. In total, 682 shot points from a pair of vibroseis units were recorded using optical fibers installed in a 9000 ft (2743 m) vertical part and 5000 ft (1524 m) horizontal reach of a well. Transmitted and reflected P, S, and converted waves were evident in the DAS data. From first-break P and S arrivals, we found average P-wave velocities of approximately 14,000 ft/s (4570 m/s) and S-wave velocities of 8800 ft/s (3000 m/s) in the deep section. We modified the conventional geophone VSP processing workflow and produced P-P reflection and P-S volumes derived from the well's vertical section. The Wolfcamp formation can be seen in two 3D volumes (P-P and P-S) from the vertical section of the well. They cover an area of 3000 ft (914 m) in the north-south direction and 1500 ft (460 m) in the west-east direction. Time slices showed coherent reflections, especially at 1.7 s (~11,000 ft), which was interpreted as the bottom of the Wolfcamp formation. Vp/Vs values from 2300 ft (701 m) -8800 ft (2682 m) interval range were between 1.7 and 2.0. These first data provide baseline images to compare to follow-up surveys after hydraulic fracturing as well as potential usefulness in extracting elastic properties and providing further indications of fractured volumes.

13.
Sensors (Basel) ; 24(10)2024 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-38793919

RESUMO

Geothermal energy exploitation in urban areas necessitates robust real-time seismic monitoring for risk mitigation. While surface-based seismic networks are valuable, they are sensitive to anthropogenic noise. This study investigates the capabilities of borehole Distributed Acoustic Sensing (DAS) for local seismic monitoring of a geothermal field located in Munich, Germany. We leverage the operator's cloud infrastructure for DAS data management and processing. We introduce a comprehensive workflow for the automated processing of DAS data, including seismic event detection, onset time picking, and event characterization. The latter includes the determination of the event hypocenter, origin time, seismic moment, and stress drop. Waveform-based parameters are obtained after the automatic conversion of the DAS strain-rate to acceleration. We present the results of a 6-month monitoring period that demonstrates the capabilities of the proposed monitoring set-up, from the management of DAS data volumes to the establishment of an event catalog. The comparison of the results with seismometer data shows that the phase and amplitude of DAS data can be reliably used for seismic processing. This emphasizes the potential of improving seismic monitoring capabilities with hybrid networks, combining surface and downhole seismometers with borehole DAS. The inherent high-density array configuration of borehole DAS proves particularly advantageous in urban and operational environments. This study stresses that realistic prior knowledge of the seismic velocity model remains essential to prevent a large number of DAS sensing points from biasing results and interpretation. This study suggests the potential for a gradual extension of the network as geothermal exploitation progresses and new wells are equipped, owing to the scalability of the described monitoring system.

14.
Sensors (Basel) ; 24(10)2024 May 19.
Artigo em Inglês | MEDLINE | ID: mdl-38794085

RESUMO

The nondestructive spectral analysis of surface waves (SASW) technique determines the shear wave velocities along the wide wavelength range using Rayleigh-type surface waves that propagate along pairs of receivers on the surface. The typical configuration of source-receivers consists of a vertical source and three vertical receivers arranged in a linear array. While this approach allows for effective site characterization, laterally variable sites are often challenging to characterize. In addition, in a traditional SASW test configuration system, where sources are placed in one direction, the data are collected more on one side, which can cause an imbalance in the interpretation of the data. Data interpretation issues can be resolved by moving the source to opposite ends of the original array and relocating receivers to perform a second complete set of tests. Consequently, two different Vs profiles can be provided with only a small amount of additional time at sites where lateral variability exists. Furthermore, the testing procedure can be modified to enhance the site characterization during data collection. The advantages of performing SASW testing in both directions are discussed using a real case study.

15.
Materials (Basel) ; 17(9)2024 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-38730878

RESUMO

This paper experimentally and analytically investigated the damage and seismic behavior of concrete walls reinforced by low-bond ultra-high-strength (LBUHS) bars. To this end, four half-scale rectangular concrete walls were fabricated and tested under reversed cyclic loading and constant axial compression. The test variables were the shear span ratio and the axial load ratio. Based on the test results, the propagation of cracks on the wall surface, the maximum strain capacity of concrete, the hysteresis loops and envelope curves, the residual drifts, and the strain distributions of LBUHS rebars were presented and discussed. The experimental results showed that all the test walls could exhibit drift-hardening capability until at least a 2.0% drift ratio if LBUHS rebars were anchored by nuts at their ends. The test results also indicated that the maximum strain capacity of concrete was above 0.86%, much larger than the currently recommended 0.4%. After unloading from the transient drift ratios of 2.0% and 2.5% for the walls with shear span ratios of 1.5 and 2.0, respectively, the measured residual drift ratios were controlled below 0.4%, which is less than the critical drift ratio (0.5%) having 98% repairable probability recommended in the FEMA document (P-58) for general concrete structures. Furthermore, a numerical method was presented to evaluate the cyclic response of the test walls, and a comparison between the experimental and the calculated results verified the reliability and accuracy of the proposed numerical method.

16.
Heliyon ; 10(9): e29554, 2024 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-38694027

RESUMO

Incised marine valleys (IVS) are hot topics in exploring the stratigraphic oil and gas-bearing plays. Multiple channelized sandstone lenses at varying depths [m], thicknesses [m], and porosities [%] constrain seismic impedance. The presence of hydrocarbon-bearing resources affects the seismic impedance (density (g/cc) and velocity (m/s)). Therefore, a quantitative prediction has been carried out for determining the thickness [m], porosity [%], and depths [m] of laterally distributed channelized sandstone lenses (SLS) for IVS, Indus offshore Basin (IOB), Pakistan, using 2-D instantaneous spectral porosity quantitative modelling (2DSSM), continuous wavelet transforms-based (CWT) 2-D instantaneous spectral density modelling (2DSSDM), and spectral decomposition tools. The 2DSSM remained limited in predicting the number of channelized sandstone lenses and their quantitative stratigraphic attributes. The 45-Hz-based processing of conventional 2DSSM has resolved the two channelized sandstone lenses of the stratigraphic trap. The deepest channelized sandstone lens has attained 1-6 m thickness with a lateral extent of 3 km, within the porosity range of 18-33 %. The highest confidence level for predicted petrophysical attributes such as 13 m-thick pay zones, -0.08, -0.067, and -0.07 acoustic impedances [g/c.c.*m/s], and 28 % porosities with R2 > 0.85 have validated interpretations. The response of 45-Hz CWT waveform-based inverted density and thickness simulations has predicted the highest thicknesses and lowest densities of reservoir sandstones within the meandering channel belt of the deepwater depositional system. The predicted densities and thicknesses for the coarse-grained sandstone lenses of point bars were 1.8-1.9 g/cc and 15 m, respectively. In the same way, the quantitative estimates of predicted density and simulated thickness have shown a strong coefficient correlation (R2 > 0.80), which confirms the presence of gas-bearing prospects within the IVS. The facies-controlled migration is thought to be the movement of the reservoir facies of the point bars and channelled sandstone-filled lenses to the side.

17.
Sci Rep ; 14(1): 10903, 2024 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-38740773

RESUMO

Assembly construction is extensively employed in bridge construction due to its ability to accelerate construction and improve quality. To speed the recovery of bridges after major earthquakes, this study proposes an assembled connection for precast piers and footings based on assembly construction. The precast piers are connected to the footings using ultra-high-performance concrete (UHPC) post-cast cupped sockets. Two specimens are tested with a 1:4 scale, namely, the cast-in-place (CIP) specimen and, the UHPC cupped socket pier specimen. Finite element models (FEM) of a continuous girder bridge with cupped socket connections are developed and verified by experimental results. The seismic fragility analysis is conducted to investigate the difference between the cupped socket connection and the CIP connection. The experimental results showed that the plastic hinge was formed on the precast piers and there was little damage to the UHPC sockets. The results of FEA indicate that UHPC cupped socket piers have slightly higher seismic fragility than the seismic fragility of cast-in-place piers. Then, some methods were proposed to reduce the seismic fragility of UHPC cupped socket piers, and their availability was confirmed by comparing them with the seismic fragility of CIP piers. Finally, an example bridge with this connection is introduced to illustrate replacing prefabricated piers after an earthquake.

18.
Sci Rep ; 14(1): 10990, 2024 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-38744957

RESUMO

Spectrum feature extraction plays a crucial role in identifying seismic events and calculating structural response parameters. However, the criteria for identifying effective modal components in Variational Mode Decomposition (VMD) are not well-defined, resulting in inaccurate spectrum feature extraction. To address this issue, we propose a novel spectrum feature extraction method that combines Allan variance, VMD, and power spectral density (PSD). Firstly, VMD is applied to filter noise components from triaxial accelerometer observations and add effective signals. Secondly, PSD is utilized to extract three groups of seismic frequencies (tri-axial accelerometers). Finally, the Allan method is introduced to identify the group of accelerometer observations with the highest reliability as the vibration frequency caused by the seismic excitation. We validate the effectiveness of our method by analyzing a Mw 2.6 micro-seismic event that occurred in Huairou, Beijing in 2022. The result shows that our proposed method accurately extracts spectrum features of the Great Wall. Specifically, the seismic excitation vibration frequencies at four monitoring stations were found to be 26.95 Hz, 12.89 Hz, 12.89 Hz, and 12.5 Hz. These findings underscore our method's utility in evaluating the Great Wall's structural response to seismic loading, which has significant implications for the conservation and protection of heritage structures.

19.
Heliyon ; 10(9): e30716, 2024 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-38765121

RESUMO

Stable continental regions pose unique challenges for conducting Probabilistic Seismic Hazard Analysis because the earthquake activity driving mechanisms are poorly understood. For instance, the lower seismicity (hence the paucity of data) and the absence of well-defined active fault systems complicate accurately determining seismic source parameters. Northeastern Brazil is a stable continental region exhibiting moderate-size events recorded with significant seismic intensities and provoking the collapse of poorly constructed buildings in the last century. Thus, assessing the seismic hazard is critical for seismic risk mitigation. The seismic hazard depends on three components: source, path, and site, and here, we present the probabilistic seismic hazard analysis of the source component for NE Brazil. Spatial aggregation of earthquake sources outlined four areal seismic zones. A goodness-of-fit test rejected the Gutenberg-Richter model of magnitude frequency distribution in one of the studied seismic zones. For this reason, we estimated the magnitude probability distribution function in that zone using a nonparametric adaptive kernel estimator. In other zones the Gutenberg-Richter magnitude frequency model was applied. In either way of the magnitude probability distribution modelling we considered the upper bound for magnitude equal to 6.6 mR, based on the upper bound of a 95 % confidence interval for the standard normal distribution of palaeoearthquake sizes. Our findings suggests that potentially damaging events are likely to occur, and we cannot neglect chances for the occurrence of earthquakes exceeding 5.2 mR. The calculated mean return periods indicate significantly shorter intervals between consecutive large events than palaeoseismic records.

20.
Heliyon ; 10(10): e31536, 2024 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-38803987

RESUMO

Seismic activities pose significant challenges to societies globally. Therefore, it is crucial to understand their occurrence, patterns, and impacts. By studying seismic activities, including earthquakes, researchers can investigate their occurrence, distribution, and characteristics which can provide effective management and risk reduction strategies. The southern part of Ghana is prone to earthquakes and this study aims to shed more light into the nature of seismic events in the area and country at large. A systematic review was conducted using the PRISMA technique across three electronic databases (SCOPUS, Dimensions and Google Scholar) to identify relevant studies published between 2000 and 2023. Extraction of data and quality assessment were performed in order to ensure reliability and validity of included studies. Results identified only 17 papers from published records to meet the inclusion criteria. Despite the grave threat earthquakes pose to vital infrastructure and human life in Ghana, research in this area remains remarkably deficient. Our findings underscore the urgent need for further study given the catastrophic potential of seismic disasters in the region. Moreover, upon scrutinizing the methodologies deployed in extant literature concerning seismic activity in Ghana, a recurring constraint that emerged was the scarce availability of data. In essence, this study offers an indispensable panorama of earthquake research in Ghana, bridging the existing knowledge chasm on seismic phenomena in the region. The insights gleaned from this review promise to fortify our comprehension of Ghana's seismic activities, thereby bolstering the country's capabilities for more effective preparedness and response strategies.

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