Earthquake Behavior Research Articles

The 2023 Mw 7.8–7.7 Kahramanmaraş earthquakes were loosely slip-predictable

Understanding the behavior of large earthquakes over multiple seismic cycles is limited by short time spans of observations compared to recurrence intervals. Most of large instrumentally-recorded earthquakes have occurred on faults lacking well-documented histories of past events. The 2023 Mw 7.8–7.7 Kahramanmaraş earthquake doublet is exceptional as it ruptured multiple segments of the East Anatolian Fault (EAF) system, where historical records of devastating earthquakes span over two millennia. Here, we use historical earthquake records, measurements of interseismic deformation, and published slip models of the 2023 events to evaluate the recurrence patterns of large earthquakes. We compare slip deficit that accrued on each fault segment since the respective penultimate events to the average coseismic slip of the 2023 doublet. We find that the coseismic slip equaled to or exceeded the accumulated slip deficit, suggesting that the slip-predictable recurrence model applies as a lower bound on strain release during the Kahramanmaraş earthquakes.

Simulating Earthquake Behavior in Steel Frames with Energy-Absorbing Links

Simulating Earthquake Behavior in Steel Frames with Energy-Absorbing Links

Strain Partitioning and Strike‐Slip Faulting in the Nanjieshan, North Tibetan Foreland: Progressive Widening of the Altyn Tagh Fault System With Implications for Regional Earthquake Hazards

AbstractLarge continental strike‐slip fault systems typically comprise a principal displacement zone and subordinate splay faults, exhibiting complex geometries, connectivity, and kinematics. Understanding the three‐dimensional arrangement of major and minor faults is important for determining strain distribution, landform development, and potential earthquake behavior. This study examines the Quaternary deformation, fault kinematics, and late Holocene ruptures along the Nanjieshan Fault system (NJSF), a major branch of the Altyn Tagh Fault (ATF) system in the North Tibetan Foreland. The E‐W‐trending NJSF comprises a principal strike‐slip fault flanked by two thrust faults, forming a regional, sinistral positive flower structure. Cosmogenic exposure dating, field data and remote sensing observations indicate that the strike‐slip rate of the main NJSF is ∼0.5 mm/a since ∼45 ka, consistent with the low slip rates observed on other faults northwest of the ATF. Paleoseismological trenches reveal three surface‐rupturing events on the NJSF in the last 2,500 years that may coincide temporally with the last two major earthquakes documented on the principal ATF, suggesting quasi‐simultaneous rupture behavior. Coulomb stress change modeling indicates that a future ATF earthquake is unlikely to trigger failure along the NJSF. Conversely, rupture of the NJSF could induce stress loading on the ATF, potentially bringing it to failure. A synchronous rupture on the ATF and its major branch faults could be facilitated by mechanically weakened fault rocks and supra‐hydrostatic fluid pressures within the deep southward‐dipping branch faults of the North Tibetan foreland. We conclude that improved prediction of future slip behavior along major strike‐slip fault systems requires detailed geochronological analysis of paleo‐earthquake events along subordinate branching faults.

Slip History, Tectonic Evolution, and Fault Zone Structure Along the Southern Alpine Fault, New Zealand

AbstractThe study of active fault zones is fundamental to understanding both long‐term tectonics and short‐term earthquake behavior. Here, we integrate lidar‐enabled geomorphic‐geologic mapping and petrochronological analysis to reveal the slip‐history, tectonic evolution, and structure of the southern Alpine Fault in New Zealand. New petrographic, zircon U‐Pb and zircon trace‐element data from fault‐displaced basement units provides constraint on ∼70–90 km of right‐lateral displacement on the presently active strand of the southern Alpine Fault, which we infer is of Plio‐Quaternary age. This incremental displacement has accumulated while the offshore part of the fault has evolved within a distributed zone of plate boundary deformation. We hypothesize that pre‐existing faults in the continental crust of the Pacific Plate have been exploited as components of this distributed plate boundary system. Along the onshore southern Alpine Fault, detailed mapping of active fault traces reveals complexity in geomorphic fault expression. Our analysis suggests that the major geomorphic features of the southern Alpine Fault correspond to penetrative fault zone structures. We emphasize the region immediately south of the central‐southern section boundary, where a major extensional stepover and restraining bend are located along‐strike of each other. We infer that this geometry may reflect segmentation of the Alpine Fault between two distinct fault segments. The ends of these proposed segments meet near where several Holocene earthquake ruptures have terminated. Our new constraints on the evolution and structure of the southern Alpine Fault help contribute to improved characterization of the greatest onshore source of earthquake hazard in New Zealand.

Investigation of the earthquake behavior of the historical Adana great clock tower using FEM updated based on environmental vibration data

In this study, the historical Adana great clock tower's dynamic characteristics (natural frequencies and mode shapes) were determined using the operational modal analysis (OMA) method. The finite element model (FEM) of the Clock Tower was updated based on the experimentally obtained dynamic characteristics. The update process was performed manually using the material properties of the Clock Tower. Linear dynamic analyses of the structures under earthquake loadings were performed using its updated finite element model. The acceleration records of the 1998 Adana-Ceyhan earthquake, scaled according to the horizontal elastic design spectrum defined in TBEC (2018) were used for dynamic input. The displacements, maximum and minimum principal stresses of the Clock Tower were obtained and evaluated. As a result of the analyses, it was determined that there was a potential for damage to the Clock Tower due to exceeding the tensile strength of the walls, but the potential for damage to the Clock Tower due to exceeding the compressive strength of the walls is weak.

Statistical distribution of static stress resolved onto geometrically-rough faults

The in-situ stress state within fault zones is technically challenging to characterize, requiring the use of indirect methods to estimate. Most work to date has focused on understanding average properties of resolved stress on faults, but fault non-planarity should induce spatial variations in resolved static stress on a single fault. Assuming a particular stochastic model for fault geometry (band-limited fractal) gives an approximate analytic solution for the probability density function (PDF) on fault stress that depends on the mean fault orientation, mean stress ratio, and roughness level. The mean stress is shown to be equal to the planar fault value, while deviations are described by substituting a second-order polynomial expansion of the stress ratio into the inverse distribution on fault slope. The result is an analytical expression for the PDF of shear-to-normal stress ratio on 2-D rough faults in a uniform background stress field. Two end-member distributions exist, one approximately Gaussian when all points on the fault are well away from failure, and one reverse exponential, which occurs when the mean stress ratio approaches the peak. For the range of roughness values expected to apply to crustal faults, stress deviations due to geometry can reach nearly 100% of the background stress level. Consideration of such a distribution of stress on faults suggests that geometric roughness and the resulting stress deviations may play a key role in controlling earthquake behavior.

Experimental investigation of EBROG and bore-epoxy anchorage methods used for interior RC beam-column joints strengthened with CFRP sheets

In severe earthquakes, the energy dissipation and ductility capacities of the structures depend on the performance of the beam-column joints where the load transfer is performed. Experiences in past earthquakes have shown that damage occurs in the beam-column joints that do not have sufficient strength and rigidity. In particular, the shear failure observed in deficient detailed joints has caused the collapse of many structures. Joints are effectively retrofitted with carbon fiber reinforced polymer (CFRP) sheets to increase the earthquake safety of the structures. However, the debonding problem experienced in CFRP sheets significantly affects the efficiency of the applied retrofit and the earthquake behavior of the member. In this study, the retrofit of reinforced concrete beam-column joints with deficient shear strength was carried out with CFRP sheets by using externally bonded reinforcement on grooves (EBROG) and bore-epoxy anchorage methods. These two retrofit methods were applied to effectively utilize the full capacity of CFRP sheets by delaying the debonding. Six ½ scaled reinforced concrete (RC) interior beam–column specimens without transverse reinforcement in the joint core were constructed. One reference and five retrofitted joints were subjected to displacement-controlled cyclic loading. The shear failures in the specimens were delayed until advanced displacement levels. The use of EBROG and bore-epoxy anchorage methods improved the yield load of the specimens by 32 % to 69.05 % compared to the reference specimen. Additionally, significant increases were observed in the initial stiffness, load-carrying, and energy dissipation capacities of the retrofitted specimens up to 68 %, 64 %, and 104 %, respectively. The ductility of the retrofitted specimens increased by approximately 7 % to 26 %. The EBROG and bore-epoxy anchorage methods proved to be highly successful in preventing the early debonding of CFRP sheets. In specimens strengthened with EBROG and bore-epoxy anchorage methods, the displacement values at which the FRP sheets began to debonding approximately doubled. It was concluded that EBROG and bore-epoxy anchorage methods were more effective than the externally bonded reinforcement (EBR) method in improving the overall structural performance of the joints.

Structural response of half-scale pumice concrete masonry building: shake table/ambient vibration tests and FE analysis

Seismic performance evaluation of masonry structures is of paramount importance for ensuring the safety and resilience of buildings in earthquake-prone regions. There are limited number of studies on pumice elements in the literature. In addition, there are almost no studies investigating the earthquake behavior of pumice masonry building as a whole structure. In this context, a comprehensive understanding of their seismic response and dynamic characteristics has been lacking. To address this knowledge gap, a shake-table experimental campaign was undertaken, wherein half-scale pumice masonry building was exposed to simulated seismic forces. To enhance the experimental findings, numerical simulations were performed to confirm and expand our comprehension of how the pumice masonry structure responds to dynamic forces. Integrating both experimental and numerical outcomes provides a holistic understanding of how pumice masonry buildings behave during seismic events. At the end of the experimental study, the frequency values of the pumice model were observed to decrease up to 23.5% in the modes compared to the undamaged state. In the numerical model, this value decreases up to 19.85%. For the undamaged and damaged model, the first three experimental mode shapes were similar to the numerical mode shapes. Both experimental and numerical results show that the expected damages occur in the same regions. These results show that nonlinear FE models can be helpful in determining potential damage model locations. The findings have implications for the seismic design and retrofitting of similar traditional masonry buildings, facilitating the development of resilient and sustainable engineering solutions in seismic-prone regions.

Earthquake Behavior Characteristics and Seismic Performance Evaluation of Phayathonzu Temple in Myanmar

Earthquake Behavior Characteristics and Seismic Performance Evaluation of Phayathonzu Temple in Myanmar

Investigation of Linear and Nonlinear Behaviour of Reinforced Concrete Column Exposed to Corrosion Effect for Different Damage Limit Levels

The high performance of reinforced concrete structural elements under the effects of lateral loads such as earthquakes is of great importance in terms of minimizing the loss of life and property that may occur due to earthquakes. One of the parameters affecting the earthquake behavior of a reinforced concrete structure is the corrosion effect. The aim of this study is to investigate the behavior of reinforced concrete columns exposed to different corrosion levels for different durations within the damage limits. In this direction, it is aimed to perform linear and nonlinear analysis of reinforced concrete columns in 5 different corrosion scenarios. In the study, nonlinear analyzes of the column were made using ANSYS software, the data obtained were determined for different damage limit levels and compared with the section analysis. Because of the study, moment-curvature relations, lateral load-horizontal displacement relations, bending ductility and plastic rotation capacity of the reinforced concrete column were determined for each corrosion scenario.

The impact of different length hooked‐end fibers on the structural performance of RC folded plates

AbstractIn this article, the effect of hooked‐end fibers with different lengths on the structural performance of RC‐FPs fabricated from hybrid fiber‐reinforced self‐compacting concrete (HFR‐SCC) was investigated. For this purpose, a total of 15 full‐scale test samples having different plate thicknesses (60, 70, and 80 mm) were produced and tested under bending after a 90‐day curing period. Subsequently, load‐carrying capacity (Pp), flexural toughness (Fth), and deflection ductility index (μu) of all RC‐FPs were found using load‐deflection curves obtained from bending tests, while crack patterns were drawn from the samples tested. Besides, high‐precision contour plots are proposed to estimate the structural performance values of RC‐FPs depending on plate thickness and fiber reinforcing index. As a result, the best structural performance in RC‐FPs was obtained from the use of a longer hooked‐end steel fiber together with micro steel fiber as a hybrid, followed by the lower length hooked‐end steel fibers as singles. Specifically, irrespective of the plate thickness, the hybrid use of longer hooked steel fibers in combination with micro fibers increased the Pp, Fth, and μu values of RC‐FPs on average 1.67, 1.76, and 1.57 times, respectively, compared to the control specimens. As for when using the lower length hooked‐end fiber as single, the values of Pp, Fth, and μu increased on average 1.57, 1.69, and 1.30 times. Lastly, whereas plate thickness has little effect on improving the structural performance of thin‐walled carrier elements such as RC‐FPs, adding fibers in different lengths, aspect ratios, and combinations is much more effective. The collective test results demonstrate that using RC‐FPs made of HFR‐SCC in the roof carrier system of large span structures could improve structural performance, aesthetics, erection time, and earthquake behavior thanks to reduced dead load.

The behavior of reinforced concrete frames exposed to high temperature under cyclic load effect

Continued use of the structure through minor renovations and repairs without a complete and accurate determination of the extent of damage to the structure and its elements exposed to high temperature effects due to fire, etc. will cause more loss of life and property in the event of an earthquake that may occur later. The aim of this study is to determine the losses on the lateral load and energy damping capacities and stiffness of reinforced concrete frames exposed to 200, 400, 600 and 800 ℃ high temperatures for 60, 120 and 180 min. For this purpose, 13 reinforced concrete frame test elements with the same concrete and steel material properties and dimensions were produced. All reinforced concrete frame test members were brought to the specified target temperature within one hour and exposed to high temperature effects for 60, 120 and 180 min at these target temperatures. The test members then allowed cooling down on their own and when they reached room temperature, they removed from the oven and subjected to cyclic lateral loading tests. The data obtained from the cyclic lateral loading tests processed to obtain lateral load - horizontal displacement, stiffness - horizontal displacement, cumulative energy consumption - horizontal displacement and strength envelope curves for each test element. According to the results of the cyclic lateral loading tests, it was determined that the lateral load carrying capacities of the test members exposed to high temperature for 60, 120 and 180 min decreased by 24 %, 33.33 % and 36 % in push, and by 25.76 %, 37.6 % and 38.72 % in pull, respectively. In addition, the energy consumption of the test elements exposed to high temperature for 60, 120 and 180 min decreased by 30.98 %, 42.41 % and 39.62 %, respectively, compared to the reference test element. The initial stiffness of all test elements exposed to the high temperature effect decreased compared to the initial stiffness of the reference test element not exposed to the high temperature effect. According to these results, the effect of high temperature causes losses in many parameters that are of vital importance in the building elements, but also highly affects the earthquake behavior of the building.

Comparison of Performance Analysis Results with Developed Site-Specific Response Spectra and Turkish Seismic Design Code: A Case Study from the SW Türkiye Region

On 6 February 2023, the Kahramanmaraş earthquakes clearly showed that the elastic spectrum curves in TBEC-2018 are insufficient to represent earthquake behavior. In this study, the effect of using a site-specific spectrum curve instead of the elastic spectrum given in TBEC-2018 on the earthquake safety of a building is investigated. For this purpose, the provinces in southwest Anatolia, Türkiye, which is one of the most tectonically complex regions with frequent seismic events, were selected. In the first stage of the study, spectrum curves were obtained for earthquakes with return periods of 2475, 475, and 72 years for each of the provinces in this region. These spectrum curves were obtained using probabilistic seismic hazard studies that take into account the active faults of the provinces and earthquake activity in both historical and instrumental periods. In the second stage of the study, analytical models of a selected model RC building were created according to each province, and static pushover analyses of these building models were performed both according to the elastic spectrum given in TBEC-2018 and according to the spectrum curve created specifically for the province. The results of the analyses show that the change in the spectrum changes the target displacement level of the buildings, and as a result, the cross-sectional damage zone of the structural elements under the earthquake effect is changed. So much so that using the site-specific instead of the elastic spectrum given in TBEC-2018 changed the damage zone of 43% of the beams and 26.4% of the columns in the İzmir model. The change in the section damage zones changed the performance level of some floors of the models and the performance level of the building. The study revealed the importance of using the most realistic elastic spectrum curves in order to determine the earthquake performance of buildings that is as close as possible to their behavior in a possible earthquake.

Determination of future creep and seismic behaviors of dams using 3D analyses validated by long-term levelling measurements

This study aims to assess the future structural performance of the Kozlu-Ulutan clay core rockfill (CCR) dam, one of the most significant water structures in the Black Sea region of Turkey, by utilizing 35 years of levelling measurements and 3D finite-difference analyses. Settlement measurements were obtained from five different points on the dam surface every 6 months. Subsequently, a three-dimensional (3D) model of the dam was created using the finite-difference method. Time-dependent creep analyses and seismic analyses were conducted sequentially, employing the Burger-Creep and Mohr–Coulomb material models, respectively. Non-reflecting boundary conditions were defined for the boundaries of the dam model. The 3D numerical analysis results were found to be highly compatible with the 35 years of levelling measurements. Additionally, the future seepage and settlement behaviors of the dam over a 100-year period (2023–2123) were analyzed, considering special time functions. Current and future seismic analyses were performed, taking into account the settlement results of the dam in 2023 and 2123. For seismic analyses, data from ten various earthquakes that occurred in Kahramanmaraş, Hatay, Malatya, and Gaziantep in Turkey in 2023 were utilized. The seismic analysis results provided significant information about the future seismic behavior of the Kozlu-Ulutan Dam, revealing notable differences between the current and future earthquake behaviors of the dam. Moreover, it was concluded that the clay core is the most crucial section concerning the current and future seismic behaviors of CCR dams. The study results emphasized the importance of continuous monitoring and periodic seismic evaluations for the safe operation of CCR dams.

Laboratory Earthquake Ruptures Contained by Velocity Strengthening Fault Patches

AbstractMany natural faults are believed to consist of velocity weakening (VW) patches surrounded by velocity strengthening (VS) sections. Numerical studies routinely employ this framework to study earthquake sequences including repeating earthquakes. In this laboratory study, we made a VW asperity, of length L, from a bare Poly(methyl methacrylate) PMMA frictional interface and coated the surrounding interface with Teflon to make VS fault sections. Behavior of this isolated asperity was studied as a function of L (ranging from 100 to 400 mm) and the critical nucleation length, , which is inversely proportional to the applied normal stress (2–16 MPa). Consistent with recent numerical simulations, we observed aseismic slip for < 2, periodic slip for 2 < < 6, and non‐periodic slip for 10 < . Furthermore, we compared the experiments where L was contained by VS material to standard stick‐slip events where L was bounded by free surfaces (i.e., L = the total sample length). The free surface case produced ∼10 times larger slip during stick‐slip events compared to the contained fault ruptures, even with identical . This disparity highlights how standard, complete‐rupture stick‐slip events differ from contained events expected in nature, due to both the free surface conditions and the heterogeneous normal stress along the fault near the free ends, as confirmed by Digital Image Correlation analysis. This study not only introduces the Teflon coating experimental technique for containing laboratory earthquake ruptures, but also highlights the utility of as a predictive parameter for earthquake behavior.

Experimental and numerical investigation of hysteretic earthquake behavior of masonry infilled RC frames with opening strengthened by adding rebar-reinforced stucco

Adding a reinforced stucco layer to the masonry infill walls is a preferred method for strengthening RC frame system structures with an easy-to-apply method that does not require a long time, is economical, and does not require detailed and extensive workmanship. However, no research has been discovered as a result of the extensive literature review that investigates the effects of masonry-infilled RC frames strengthened with a reinforced stucco layer on the seismic performance of openings that must be due to architectural requirements such as doors, windows, installations, and similar ventilation systems. As a result, an experimental study was planned to investigate the effects of the dimensions and location of the opening in the masonry infill walls on the performance of the strengthening method with the reinforced stucco layer. The applied strengthening method increased the ultimate load capacity, initial stiffness, and energy dissipation capacity values of reinforced concrete frames with masonry infill walls by 83%, 226%, and 62%, respectively, but resulted in a 38% decrease in displacement-ductility ratios. The study found that the openings in the masonry infill walls harm the performance of the strengthening technique by adding a rebar-reinforced stucco layer and decreasing the success level. When the opening size increased, and the opening was located at the corner of the masonry wall, the performance of the applied strengthening technique was negatively affected and decreased. Furthermore, nonlinear numerical analyses of the experiments conducted as part of the study were performed using ABAQUS finite element software. The numerical analysis results were compared to the experimental results. It has been determined whether numerical analysis models are compatible with experimental results.

Manufacture of a Simple One-Way Vibration Table and Earthquake-Safe Structure Model as Props in The Strengthening Structural Method

The problem raised is the absence of earthquake-safe structural props as learning support, so students still struggle to describe the behavior and effects of earthquakes on buildings. This research aims to produce earthquake-safe structural props media that are feasible to use as learning support media in the Structural Reinforcement Methods course. This research uses the Research and Development method, which adapts the DDD-E model, which consists of the Decide, Design, Develop, and Evaluate stages. The instrument used in this research is an assessment questionnaire for the media validation and practicality tests. Based on the product assessment of the earthquake-safe structure props media in the course of Structural Reinforcement Methods with the Aiken formula by media experts from all aspects obtained a V Aiken value of 0.87 with valid criteria, and the assessment by material experts from all elements received a V Aiken value of 0.96 with valid criteria. At the same time, students' practicality test of the earthquake-safe structure props media obtained a percentage value of 87% with very practical criteria. Therefore, the produced media can be declared very valid and applicable as learning support media.

Along-Strike Variation of Rupture Characteristics and Aftershock Patterns of the 2023 Mw 7.8 Türkiye Earthquake Controlled by Fault Structure

Abstract On 6 February 2023, an Mw 7.8 earthquake occurred along the East Anatolian fault zone (EAFZ) in southeastern Türkiye, representing the strongest earthquake in the region in nearly 80 yr. We investigate rupture characteristics and aftershock patterns of the earthquake through focal mechanism calculation, backprojection analysis, and finite-fault inversion. The results show bilateral rupture propagation of the mainshock with transient supershear speed in the southwest portion of the EAFZ, as well as shallower coseismic slip and abundant normal-faulting aftershocks in the same portion. We attribute these earthquake behaviors to the along-strike variation of fault structure of the EAFZ, which features a more complex fault geometry accompanied by numerous short normal faults in the southwest portion. These results shed light on fault segmentation, rupture speed variation, and slip partitioning along the EAFZ, advancing our understanding of fault structural control on earthquake behaviors in a complex multisegment fault system.

Effect of soil types on nonlinear earthquake behavior of buildings

The Winkler method, which is widely used today, assumes that the soil behaves elastically and does not take into account the soil shear stress values, it is insufficient to reflect the actual soil behavior. Especially in the earthquake calculations of rigid and massive structures such as high-rise buildings, dams, suspension bridges, viaducts, it is necessary to consider soil as a dynamic system that changes shape and affects the behavior of the structure in terms of inertia. In response to the effect of soil on the structure, the structure also affects soil both kinematically and dynamically. Thus, in the absence of the structure, the earthquake data, which is only a result of the dynamic behavior of the soil in its internal structure, now acquires a more complex soil motion characteristic that is also affected by the presence of the structure. The observations made in some earthquakes show that the changes between the records taken simultaneously on the building foundation and at soil surface not a point far from foundation, show that the structure also affects soil therefore soil motion in response to the effect of the earthquake on the structure. In this study, the effect of soil types on the nonlinear seismic behavior of reinforced concrete structures was investigated. For this purpose, 7-storey building models with different plans and rigidities were created. The behavior of these models under 11 different earthquake loads for the ZA, ZB, ZC, ZD, ZE soil types specified in the Turkish Building Earthquake Code has been investigated. Analyzes were made using the time history method with the help of the SAP2000 program. As a result of the analysis, the displacements, plastic hinge formation, Effective inter-storey drift and period values obtained for different models were compared.

Earthquake behavior of flat slab structures, particularities and opportunities for use in the building stock of the Chisinau municipality

The Republic of Moldova is characteristic for active seismic phenomena and there is always a direct danger of strong earthquakes. The building stock of the country has a complex character, this aspect is manifested in the municipality of Chisinau, where we have different buildings in terms of materials used, structural systems and height regime. New trends in construction are focused on buildings with a load-bearing frame structural system and a frame with a flat slab structure. The usual design practice is characteristic for the implementation of beam-column systems, where the plates are supported by the beams and the beams are supported by the columns. Nowadays, for the residential buildings design, a more elegant and ergonomic floor system is used - the flat slab system. Therefore, the slabs are subjected to increased loads, which requires special attention in the design and implementation of these types of structures.