Aftershock Events Research Articles

The 2024 Mw 7.0 Wushi Earthquake in Southern Tianshan Convergent Zone: Finite-Fault Model for the Coseismic Rupture and Aftershock

Abstract On 22 January 2024, an Mw 7.0 earthquake struck the oblique thrust Maidan fault (MDF) at the boundary between the Southern Tianshan and Tarim basin, making it the largest earthquake on the fault in the last 100 yr. Here, we use Interferometric Synthetic Aperture Radar (InSAR) to retrieve coseismic and aftershock deformation caused by the earthquake and then constrain fault geometry and slip distribution. Line-of-sight InSAR observations revealed a coseismic deformation area of 70 km × 60 km with a maximum value of ∼0.8 m and also captured the deformation from the aftershock event seven days after the mainshock. Our preferred two-segment coseismic fault model ruptures the MDF locked segment and deeper regions, exhibiting a homogeneous elliptical rupture with a maximum slip of ∼2.7 m on a rectangular plane with a dip angle of ∼60°, a length of ∼55 km, and a depth between 5 and 20 km. The aftershock formed a rupture plane of 10×8 km2 with the maximum slip of ∼0.3 m, causing slip in the shallow area of the fault where the coseismic ruptures were smaller, and supplementarily released the stress in the shallow part of the fault. The strong earthquake (Mw 7) return period on MDF inferred from the interseismic slip rate is 170–200 yr. Oblique thrust slip revealed by the slip distribution model is the result of long-term absorption of oblique convergence strain in the Southern Tianshan by the MDF and then concentrated release. The 2024 event resulted in a 60 km unruptured segment on the MDF being in a stress-triggering zone, increasing the potential seismic hazard, in contrast to the delayed seismicities on 100 km region of the southern Kalping fault (KPF).

Time-Dependent Aftershock Probabilistic Forecasting and Ensemble Model Implementation: Insights from the 2021 Ms 7.4 Maduo Earthquake

Abstract On 22 May 2021, an Ms 7.4 earthquake with a focal depth of 17 km struck the Maduo region of Qinghai province, breaking a 3.8-year quiescence of strong earthquakes (magnitude >7.0) in mainland China. This event has increased stress on the Maqin–Maqu segment of the Kunlunshan fault, heightening the potential for a large earthquake in the region. In this study, we employed the epidemic-type aftershock sequence (ETAS) model and Reasenberg–Jones (R–J) model to fit the aftershock sequence following the mainshock, analyzing the temporal response and its ability to influence future generations. Concurrently, ensemble models were explored to leverage the strengths of both the ETAS and R–J models. Short-term forecasts of the probability and occurrence rate of aftershock events with varying magnitudes were conducted for the next three days. Then statistical methods, that is, receiver-operating characteristic diagrams and information gain, were used to evaluate the unconditional and relative performance. Our findings include that the ETAS model indicates a high decay rate with many aftershocks triggered by previous events, whereas the R–J model shows a normal decay rate with a higher proportion of strong aftershocks. The ETAS and R–J models perform better than random guesses for different aftershock magnitudes, but the ETAS model is somewhat affected by the problem of missing small earthquakes for a short period of time after the mainshock. The ensemble model that chooses the minimum strategy shows promise, especially in the early period, suggesting a reasonable and cautious decision approach should be chosen during the unstable stage. This study highlights the importance of short-term aftershock probability estimation for seismic research and decision-making. In the absence of more accurate models, current analytical approaches within the operational earthquake forecasting framework remain valuable. Continuous testing, feedback, and refinement of forecasting models, along with the development of ensemble models, are essential for enhancing seismic risk assessment and mitigation strategies.

Performance of AI-Based Phase Picking and Event Association Methods after the Large 2023 Mw 7.8 and 7.6 Türkiye Doublet

ABSTRACT On 6 February 2023, a devastating earthquake doublet consisting of Mw 7.8 and 7.6 events separated by about 9 hr struck the southeastern part of Türkiye. The developing aftershock sequence contained thousands of events during the first few days and overwhelmed the routine algorithms handling their detection and location. In addition, several stations temporarily lost real-time contact and came online again later. At the same time the Omori decay of the aftershock event rate reduced the event frequency and allowed for inclusion of progressively smaller-magnitude events with time. One possibility to help deal with such a complex situation is the use of machine learning (ML) methods to generate earthquake catalogs with a substantially higher number of events. Here, we present high-resolution earthquake catalogs derived with two ML association methods for the first five days of the aftershock sequence of this doublet. In terms of the number of reliably located events, the event catalog created from PhaseNet picks and the GENIE phase association method outperforms both the routine regional catalog and the second ML-derived catalog obtained from the GaMMA phase association method. Although both GaMMA and GENIE catalogs detect about 6 times more events than the routine catalog, GENIE associates on average about double the phases to a single event than GaMMA, which results in better constrained event locations. The spatiotemporal evolution of the event rates is sensitive to changes in the network geometry due to variable station availability. During the first few days, no decay of the event rate in the enhanced catalog is observed due to the inclusion of progressively smaller-magnitude events with time and increased station availability. This study indicates that ML-derived earthquake catalogs for challenging time periods like the early aftershock sequences of large earthquakes have the potential to significantly improve routine event catalogs.

Co-seismic deformation and related hazards associated with the 2022 Mw 5.6 Cianjur earthquake in West Java, Indonesia: insights from combined seismological analysis, DInSAR, and geomorphological investigations

IntroductionOn November 21, 2022, a magnitude Mw 5.6 earthquake struck Cianjur Regency in the West Java Province of Indonesia. It was followed by at least 512 aftershocks that persisted from November to June 2023. This seismic event occurred in an area previously unrecognized as an active fault zone. The consequences of this earthquake in Cianjur were severe, leading to both loss of life and extensive structural damage. The substantial damage to buildings was likely a result of abrupt alterations in the local topography due to surface deformation effects.ObjectivesThis research endeavor aims to spatially determine the patterns of ground surface deformation and its relationship with local geomorphological setting due to earthquakes in Cianjur in 2022.MethodsIn this study we conduct seismological analysis of 45 seismic stations, statistical analysis of mainshock and aftershocks data, RADAR Sentinel-1 imagery and employed the DInSAR methodology. Field survey was also conducted to determine the geomorphological characteristics in the study area.ResultsThe outcomes disclosed that the deformation encompassed both subsidence and uplift. The results signify that there was subsidence deformation in the vicinity of Cianjur and its environs during the primary earthquake on November 21, 2022, with an average deformation value of approximately -5 cm. In contrast, the measured deformation during the aftershocks exhibited uplift deformation, with an average value of 10 cm. The examination of deformation patterns amid the 2022 Cianjur earthquake sequence detects elevated deformation values in the vicinity of Cugenang district, with an orientation running from northwest to southeast. The geomorphological investigation conducted indicates that the region of Cianjur encompasses a variety of landforms, such as volcanic, structural, fluvial, and denudational. These landforms exhibit distinct responses to seismic activities. Co-seismic hazards, such as landslides frequently occur as a consequence of seismic events in mountainous terrain.Main ConclusionsSpatio-temporal variation of ground deformation could arise from various causes, such as the number and distribution of aftershocks, stress redistribution, fault interactions, secondary effects, and local geological settings. The mainshocks release accumulated stress along a fault, resulting in particular types of deformation, whereas aftershocks may redistribute stress exhibiting on adjacent faults. Secondary effects triggered by aftershocks, coupled with local geological and geomorphological conditions, further contribute to the diverse patterns of ground deformation observed during seismic events. The results of the study revealed that ground deformation had the greatest impact on fluvial, volcanic, and denudational processes, resulting in notable subsidence and uplift in specific regions. The occurrence and magnitude of co-seismic landslides were triggered by both mainshock and aftershock events, which occurred on weathered geological materials. These effects were further amplified by the simultaneous presence of the rainy season.ImplicationsThe knowledge gained from this research can be applied to evaluate the impacts of earthquakes and to proactively reduce future risks.

Instrumentation of the Nigeria network of seismological stations

“Living in fear of Nigeria biggest Earthquake” is a sub-heading of the Punch daily newspaper of Nigeria, dated, 21st of August, 2016, reported the earthquake/tremor recently witnessed in the ancient town of Saki, accompanied by a series of aftershock events that lasted for about three (3) months (March/May, 2016) southwest Nigeria[1]. Similarly, roughly five (5) years later, another series of earthquakes/tremors occurred again in Saki town, which was reported by an online news vendor named “Ripples Nigeria” dated September 8, 2021, under the sub-heading of “earth tremor rocks Saki in Oyo state”[2]. However, these events were not captured nor recorded by any of the functional seismological stations in Nigeria. The nearest seismological station located at the Obafemi Awolowo University (OAU) Ile-Ife, also failed to capture the events. We therefore seek to examine the instrumentation of the Nigerian National Network of Seismographic Stations. This is necessary to understand the functionalities and the capabilities of the deployed seismometers in each of the seismic stations. Therefore, we evaluated the bandpass limit of the seismic wave frequency for the respective seismic stations in Nigeria through the computation of the amplitude-frequency response curve, phase response curve, and count to cm/sec.

Displacement-based design procedure for the seismic retrofit of existing buildings with self-centering dissipative braces

Existing framed buildings, especially those designed according to outdated seismic codes, often offer inadequate seismic protection levels due to material degradation, low amount of reinforcement and poor construction details. Among the possible retrofit strategies, elasto-plastic dissipative braces (EPDBs) can be installed to provide supplemental stiffness and energy dissipation in the main resisting frame. Since they are based on the plastic deformation of sacrificial steel components, EPDBs are inherently affected by scarce recentering capability, i.e., presence of residual deformation at the end of the mainshock that could impair their effectiveness for aftershock events. As demonstrated in recent seismic sequences, there might be not enough time to restore (e.g., though hydraulic actuators and a reaction frame) the undeformed configuration of the structure before a subsequent shock. This issue can be overcome through self-centering dissipative braces (SCDBs), i.e., braces equipped with dampers characterized by a “flag-shaped” hysteretic behavior, which inherently facilitates the immediate re-centering of the frame. Despite this evident benefit, there is still lack of practical design procedures for the seismic retrofit of buildings through SCDBs. To fill this gap, a direct displacement-based design procedure for SCDBs tailored to building frames is here conceived and illustrated. The proposed method aims at achieving simultaneously two performance requirements: (i) a target maximum roof displacement under the ultimate-limit-state seismic event; (ii) the absence of significant residual inter-storey drifts at the end of the shaking. The implementation of the procedure is described by two applications to a steel and to a reinforced concrete case-study building. Nonlinear time-history analyses are carried out to prove the effectiveness of the proposed method, along with a comparison of the seismic performance offered by SCDBs versus traditional EPDBs implemented in the same case-study buildings.

A High-Resolution Aftershock Catalog for the 2014 Ms 6.5 Ludian (China) Earthquake Using Deep Learning Methods

A high-resolution catalog for the 2014 Ms 6.5 Ludian aftershocks was constructed based on the deep learning phase-picking model (CERP) and seismic-phase association technology (PALM). A specific training strategy, which combines the advantages of the conventional short–long window average energy ratio algorithm (STA/LTA) and AI algorithms, is employed to retrain the CERP model. The P- and S-wave phases were accurately detected and picked on continuous seismic waveforms by the retained AI model. Hypoinverse and HypoDD were utilized for the precise location of 3286 events. Compared to the previous results, our new catalog exhibits superior performances in terms of location accuracy and the number of aftershock events, thereby enabling a more detailed depiction of the deep-seated tectonic features. According to the distribution of aftershocks, it can be inferred that (1) the seismogenic fault of the Ludian earthquake is the NW-trending Baogunao–Xiaohe Fault, (2) the Ludian aftershocks interconnected with the discontinuous NW-trending Baogunao–Xiaohe Fault, and they also intersected with the Zhaotong–Ludian Fault. (3) This suggests that the NE-trending Zhaotong–Ludian Fault may have been intersected by the NW-trending Baogunao–Xiaohe Fault, indicating that the Baogunao–Xiaohe Fault is likely a relatively young Neogene fault.

Use of temporary seismometers collecting aftershock events for non-ergodic site term development

Use of temporary seismometers collecting aftershock events for non-ergodic site term development

SEISMIC FRAGILITY EVALUATION OF SOIL-PILE-STRUCTURE INTERACTION EFFECTS SUBJECTED TO MAINSHOCK-AFTERSHOCK RECORDS

In most current seismic design on bridges, only mainshock actions are considered without incorporating the effect of mainshock-aftershock (MA) sequences and interaction soil-pile.However, a large mainshock usually triggers numerous aftershocks in a short period. This paperstudy the effect of mainshock-aftershock sequences on the behavior of interaction Soil-pile-structure system (ISPS). abeam on nonlinearWinkler foundation (BNWF) model is usingand subjected to non-linear static analysis and incremental dynamic analysis (IDA) leading finally to the fragility curves which are developed. These analyses aim to capture the collapse state of structures under aftershock events preceded by various mainshock levels. Results obtained from capacity curve, incremental dynamic and fragility curves of ISSP system.The analytical results show that in the MA sequences,for dense soil the vulnerable of mainshock-aftershock (MS-AS) loading are more damage due to mainshock loading for all diameter of the pile and the mass. For soft soil are more vulnerable to damage due to mainshock-aftershock (MS-AS) loading. But in the stiff clay the effect of mainshock-aftershock (MS-AS) loading for all the diameter of pile and for masse are neglected.
 Keywords:bridge,interaction soil-pile-structure, Winkler foundation, dynamic analysis, fragility curves,mainshock-aftershock.

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.

Rapid estimation of seismic intensities by analyzing early aftershock sequences using the robust locally weighted regression program (LOWESS)

Abstract. Accurate and rapid assessment of seismic intensity after a destructive earthquake is essential for efficient early emergency response. We proposed an improved method, AL-SM99, to assess seismic intensity by analyzing aftershock sequences that occur within 2 h of mainshocks. The implementation effect and application conditions of this method were illustrated using 27 earthquakes with Mw 6.5–8.3 that occurred globally between 2000 and 2023. When the fault system in the seismic region is clear and simple, the robust LOWESS-fitted (locally weighted regression program) curves could be used to estimate the location and length of the fault rupture. LOWESS results can indicate the overall rupture trend and make reliable rupture-scale judgments even when the fault system is complex. When Mw ≥ 7.0 and the number of aftershocks exceeds 40, the AL-SM99 intensity evaluation results may be more reliable. Using aftershock catalogues obtained by conventional means allows for a stable assessment of seismic intensities within 1.5 h of the mainshock. When the number of aftershocks is sufficiently large, the intensity assessment time can be greatly reduced. With early accessible aftershocks, we can quickly determine the rupture fault planes and have a better estimate of the seismic intensities. The results of the intensity assessment provide a useful guide for determining the extent of the hardest-hit areas. By expanding the data sources for seismic intensity assessment, the early accessible data are utilized adequately. This study provides a valuable reference point for investigating the relationship between early aftershock events and fault rupture.

Cianjur M5.6 Earthquake Aftershock Survey (CEAS) Using ITB Temporary Seismographs

Western Java, part of the Sunda Arc, is an active tectonic region with high seismicity. The tectonic activity has produced active faults which are located near densely populated areas. On November 21, 2022, a significant earthquake rocked the Cianjur region, West Java, causing severe damage and loss of life. In this study we acquired aftershock data which was generated from the Cianjur M5.6 earthquake. Twenty stations consisting of 19 Smartsolo IGU-16HR 3C 5 Hz Seismometer (short-period type) and 1 Guralp 6TD 30s to 100 Hz Seismometer (broadband type) were deployed to monitor aftershocks from 22 November to 23 December 2022. The seismograph stations were deployed covering the earthquake source area and tectonic features in the Cianjur region. The results show that the aftershock events is clearly recorded at 20 stations with an average difference between the arrival times of the S waves and P waves (Ts-Tp) of 2 seconds. A total of ±500 earthquake events were obtained consisting of ±4000 P wave phases and ±3000 S wave phases with a Vp/Vs ratio value of 1.72 and RMS error less than 0.1 second. The Cianjur M5.6 earthquake was classified as a shallow crustal seismicity with a strike slip fault mechanism, hypocenters were generally distributed at a depth of 3-10 km.

Understanding fabric evolution and multiple liquefaction resistance of sands in the presence of initial static shear stress

Recent field observations have shown that mainshock and subsequent aftershock events can induce multiple-liquefaction events, in which soil liquefies several times at the same site. However, the fundamental mechanism of multiple liquefaction in most previous studies is under level ground conditions, and the cyclic loading condition is symmetric under such conditions. In this study, we conduct 3D DEM simulations of multiple-liquefaction processes considering initial static shear stress. 14-sphere clumped models are used to reconstruct the realistic grain shape of Toyoura sand particles. Cyclic liquefaction and reconsolidation tests are carried out alternately five times. The soil samples with various initial static shear stresses are sheared up to different maximum shear strains in each liquefaction stage. We investigate the liquefaction behavior and volumetric compression during multiple-liquefaction stages considering initial static shear stress. In addition, the evolution of contact-based fabrics, including coordination number (Z) and degree of fabric anisotropy (ac), are analyzed during the whole liquefaction and reconsolidation tests. Furthermore, we establish the relations among contact-based fabrics (Z and ac), volumetric compression and liquefaction resistance. The results reveal that in stress reversal cases, the maximum shear strain is the governing factor that influences the multiple-liquefaction resistance. Conversely, the static shear stress becomes the dominant factor affecting the multiple-liquefaction resistance in non-stress reversal cases. Moreover, changes in multiple-liquefaction resistance are attributed to the microstructure of soils represented by Z after reconsolidation.

A Non-Extensive Statistical Physics View of the Temporal Properties of the Recent Aftershock Sequences of Strong Earthquakes in Greece

Greece is one of Europe’s most seismically active areas. Seismic activity in Greece has been characterized by a series of strong earthquakes with magnitudes up to Mw = 7.0 over the last five years. In this article we focus on these strong events, namely the Mw6.0 Arkalochori (27 September 2021), the Mw6.3 Elassona (3 March 2021), the Mw7.0 Samos (30 October 2020), the Mw5.1 Parnitha (19 July 2019), the Mw6.6 Zakynthos (25 October 2018), the Mw6.5 Kos (20 July 2017) and the Mw6.1 Mytilene (12 June 2017) earthquakes. Based on the probability distributions of interevent times between the successive aftershock events, we investigate the temporal evolution of their aftershock sequences. We use a statistical mechanics model developed in the framework of Non-Extensive Statistical Physics (NESP) to approach the observed distributions. NESP provides a strictly necessary generalization of Boltzmann–Gibbs statistical mechanics for complex systems with memory effects, (multi)fractal geometries, and long-range interactions. We show how the NESP applicable to the temporal evolution of recent aftershock sequences in Greece, as well as the existence of a crossover behavior from power-law (q ≠ 1) to exponential (q = 1) scaling for longer interevent times. The observed behavior is further discussed in terms of superstatistics. In this way a stochastic mechanism with memory effects that can produce the observed scaling behavior is demonstrated. To conclude, seismic activity in Greece presents a series of significant earthquakes over the last five years. We focus on strong earthquakes, and we study the temporal evolution of aftershock sequences of them using a statistical mechanics model. The non-extensive parameter q related with the interevent times distribution varies between 1.62 and 1.71, which suggests a system with about one degree of freedom.

Rapid mapping of seismic intensity assessment using ground motion data calculated from early aftershocks selected by GIS spatial analysis

Following a major earthquake, disaster information services must deliver accurate damage assessment results during the emergency ‘black box’ phase when data is scarce. Seismic intensity maps contain crucial information for determining the damage in the affected area. For earthquakes with Mw between 5.5 and 7, this study proposes using GIS analysis to mine aftershock events in early aftershock sequences that are closely related to the mainshock fault, and then using these events to generate seismic intensity assessment maps. Regression curves were first obtained using a nonparametric method (rLowess) to analyse the geographical coordinates of early aftershocks. Then, a buffer of 1 or 1.5 km radius was made for the curve, and the aftershocks in the buffer were used to calculate the predicted peak ground velocity (PGV) values over a specific km-grid range. Finally, rapid mapping of seismic intensity was assessed based on the intensity scale. This straightforward and repeatable method employs seismic station data obtained shortly after the mainshock. The assessed seismic intensity accurately reflects the location and extent of the hardest hit areas and can be cross-referenced with geophysical results to accurately assess the damage in the affected areas.

Seismic waves of the 10 December 2020 M6.6 Yilan earthquake observed by interferometric fiber-optic gyroscope

A newly developed cost-effective fiber-optic gyroscope (FOG) and an existing seismometer co-locating at the campus of National Central University (NCU) recorded seismic waves of a M6.6 Yilan earthquake and aftershock events occurring at around 24.74° N 122.03° E (88 km away from NCU) during 10–11 December 2020. Two nearest accessible broadband seismographs located in Hsinchu have also been employed as measurement references for facilitating the analysis of the detected seismic signals. Conventional seismometers usually detect the translational components of the seismic waves, while the FOG observes the rotational component. The recorded FOG data exhibit high-resolution details of the rotational component of shockwaves, which provides additional information of seismic waves. The shock waveforms of the translational and rotational components, analyzed under the conservation of the shock wave energy density received by FOG and seismograph, are found to be significantly correlated. The correlation coefficients of 60-s data are > 0.85 for the main shock and > 0.86 for the aftershock, while those of the 10-s peak periods are as high as 0.9064 and 0.8953, respectively. The highly correlated data imply that the energy registered by the two devices are equivalent. The optical interference-based rotation senor of the cost-effective FOG provides a high sensitivity of better than 3.6 deg/h and an extended dynamic sensing range as high as 55 dB with the fully sensing ability from pm 3.6 deg/h to pm 720,000 deg/h. The FOG seismometer sheds some light on building an earthquake six-degree-of-freedom observation array to have a bettering on the understanding of the seismicity.

3D DEM Simulation on the Reliquefaction Behavior of Sand Considering the Effect of Reconsolidation Degree

ABSTRACT More and more earthquake cases demonstrate that sandy deposits may be more prone to becoming liquefied again in aftershock events. This phenomenon has also been authenticated by some laboratory element tests and shaking table tests. However, most of the existing studies on reliquefaction only put particular emphasis on the completely reconsolidated soil. Due to the possible short time interval between the main shock and its aftershock events, the generated pore pressure in soil deposits may not have completely dissipated when the aftershock occurred; the reliquefaction is more likely to occur under incomplete consolidation conditions. To investigate the reliquefaction behaviors and the related microscopic mechanisms for the incompletely and completely reconsolidated soil, a series of numerical cyclic triaxial tests are performed in this study via the 3D Discrete Element Method (DEM). Results demonstrated that the reliquefaction resistance of soil is significantly affected by the residual strain and the reconsolidation degree. From the microscopic point of view, the fabric anisotropy and the tightness of inter-particle contacts are the main factors affecting the reliquefaction resistance.

Experimental Hybrid Simulation of Severe Aftershocks Chains on Buildings Equipped with Curved Surface Slider Devices

In this research work the outcomes of a hybrid experimental campaign are analyzed, in order to evaluate the influence of aftershock events on the frictional response of sliding-based isolation devices for buildings. To achieve this, a hybrid testing framework was accordingly defined, by considering a numerical substructure, in terms of a simplified analytical model of a case study structure, and a physical substructure, as a full-scale Curved Surface Slider device, tested within the Bearing Tester System of the EUCENTRE Foundation Laboratory in Pavia (Italy). The tested isolator was equipped with a special sliding material, made up of a Poly-Tetra-Fluoro-Ethylene-based compound (PTFE), filled with carbon fibers and with a solid lubrication. The hybrid tests were performed, in terms of earthquake simulations, and the response of the base-isolated structural system was computed, by applying single-events, rather than aftershock chains. Results lead to a better understanding of the behavior of sliding-based seismic isolation systems, characterized by medium-to-high tribological properties, in terms of peak and residual displacements for both the single-event and the mean responses. Specifically, this work provides hybrid experimental evidence of the influence of an initial displacement offset on the overall behavior of the considered structural system.

Analysis of Multistorey RCC Frame subjected to Mainshock and Aftershock Earthquake

Abstract: Structure analysis and design are significantly influenced by earthquake. It is believed that seismic evaluation is required for the viability and serviceability of both present and future building structures. When a structure's base is subjected to a certain type of ground motion, a time history analysis is performed to examine the dynamic reaction of the structure at each time interval. The near-field earthquake ground motion verification may have specific impacts for both forward and backward directivity. The initial's velocity and displacement motions, respectively, exhibit pulse and fling-step characteristics. Therefore, it is crucial to assess how well structures built solely to withstand the primary shock would work through future aftershocks. Using modern seismic protection systems, such as base isolations or / and supplemental dampening devices, that significantly reduce building damages during main shocks and their related aftershocks is one of the appropriate solutions to this issue. Due to changes in both static and dynamic stress that take place during the earthquake process, aftershock events are set off by the primary shock. In order to better understand the ground motion features of a sizable collection of mainshock and subsequent aftershock ground motion data recorded in accelerograph stations around the region, this study reviews pertinent literature in the field. The G+9 RCC building will be used in this study to conduct a time history analysis of the mainshock and aftershock data of the Chamoli earthquake provided by the Centre for Engineering Strong Motion Research Ground Motion Database. For designing purposes, the IS 456-2000 code is taken into consideration. Live loads are measured in accordance with IS 875-part 1, and seismic zone IV is selected for analysis in accordance with IS 1893-2016. Storey drift, base shear, joint reactions, and storey displacement are just a few of the variables that can have an impact on how well a building performs. Since each of these variables has a significant impact on how a structure responds to seismic loads, they are also taken into account when evaluating the results.

Application of Convolutional Neural Network to GIS and Physics

Human life and property are often seriously threatened and lost due to natural disasters such as earthquakes. As a spatial information system, the geographic information system (GIS) can collect, store, and manage the local or whole related physical data of the surface space to be measured with the support of software and hardware. The physical data is collected through GIS for performance testing. The data are collected from the aftershock event records of the Wenchuan earthquake. Among them, 14,000 Wenchuan earthquake events are used as the original data set, and 8,800 aftershock events are used as the test data set. Seismic data involves the detection of multiple physical quantities, which makes the seismic data gradually increase, many data have no obvious linear relationship, and traditional detection methods are difficult to meet the detection requirements. The artificial intelligence method led by a convolutional neural network (CNN) can perform pattern matching on complex nonlinear variables, and models with general characteristics can be generated from different seismic waveforms for the prediction of seismic waveforms. The results show that GIS can effectively intercept and collect seismic physical signals. The training and detection accuracy of CNN combined with GIS physical data is higher than 90%. Compared with traditional training methods, CNN is obviously superior in detection accuracy and recall rate. At the same time, a large number of microseismic events that are easily missed by manual selection can also be found.