The research, led by Guan Chen of the Earth Observatory of Singapore and the National University of Singapore, together with Siau Chen Chian, Michael Beer, and Shengji Wei, addresses a persistent gap in seismic hazard analysis. Engineers can already estimate how strong ground shaking will be at a given distance from an earthquake of a certain size using ground-motion prediction equations. What has been harder to quantify is the impulsive character of near-fault motion — how long the dominant pulse lasts, how large its velocity amplitude is, and how these quantities vary with the seismological setting. The new work links pulse parameters directly to magnitude, distance, and site stiffness, giving hazard analysts a physically grounded way to generate realistic near-fault ground motions for any scenario of interest.

The first technical challenge the team tackled was identification. Not every record close to a fault contains a clear pulse, and distinguishing pulse-like from non-pulse-like ground motions has traditionally relied on wavelet-based classification methods, most famously the approach introduced by Jack Baker in 2007. Many existing identification procedures, however, tend to extract a single type of pulse from a record, which can miss the richer structure of real near-fault motions. Records from large continental earthquakes frequently contain multiple pulses, arising from forward-directivity effects as the rupture front races toward the site, from fling-step associated with permanent tectonic deformation, or from constructive interference of seismic waves with basin geometry. A method that captures only one pulse type risks underrepresenting the destructive potential of the motion.

To overcome this limitation, the researchers developed a novel extraction procedure that integrates a parametric pulse model with the generalized continuous wavelet transform, or GCWT. The parametric model provides a mathematical description of the pulse shape, while the wavelet transform scans the velocity time series across scales and times to locate the energy concentration that corresponds to the pulse. By combining the two, the procedure can capture various types of pulses within a single record, preserving both the diversity and the accuracy of the extracted signals. The authors report that the pulses extracted by their method effectively match the pulse characteristics visible in the original records, a critical validation step before any statistical modeling can proceed.

Armed with this identification tool, the team mined the PEER NGA-West2 database, one of the largest curated collections of strong-motion recordings from shallow crustal earthquakes worldwide. Out of 21,222 records examined, 815 were identified as pulse-like ground motions. This carefully classified dataset forms the empirical backbone of the study. Each pulse-like record was decomposed into its pulse component and a residual component, and the parameters describing the pulse — including its period, amplitude, and the number of significant cycles — were tabulated alongside the corresponding earthquake magnitude, source-to-site distance, and Vs30 for each station.

The second major contribution is a set of empirical regression models that predict the pulse parameters from these three explanatory variables. The functional form of the models was developed with attention to the underlying physics: larger earthquakes produce longer rupture durations and hence longer pulse periods, pulses attenuate with distance as seismic energy spreads and is absorbed, and soft soil sites can amplify and lengthen the dominant velocity cycles relative to stiff rock. Model uncertainty was quantified through residual analysis, following the random-effects regression framework that has become standard in ground-motion modeling since the work of Abrahamson and Youngs in 1992. The proposed models were then validated against existing pulse models and against independent datasets not used in the calibration, providing confidence that the predictions generalize beyond the fitting sample.

A particularly valuable practical outcome of the study is a workflow for synthesizing near-fault broadband ground motions. The approach combines the empirical pulse model with a stochastic representation of the residual component — the high-frequency, incoherent part of the motion that remains after the coherent pulse is removed. Because the pulse and the residual are treated separately, the resulting artificial ground motions retain the distinctive impulsive features that govern structural response while simultaneously matching the spectral velocity and spectral acceleration of benchmark recordings across a broad frequency range. This two-component strategy echoes the spectral representation method in stochastic process simulation and offers a computationally efficient alternative to full physics-based rupture simulations, which remain expensive for routine hazard applications.

The implications for earthquake engineering are substantial. Previous research has demonstrated that near-fault pulses impose large deformation demands on flexible structures: moment-resisting frames subjected to pulse-like records accumulate damage differently than those subjected to ordinary shaking, and offshore wind turbines, tunnels, and seismically isolated buildings all show heightened vulnerability when the impulsive content of the motion is ignored. By providing pulse parameters conditioned on magnitude, distance, and site class, the new model allows analysts to construct scenario-consistent suites of near-fault motions without waiting for the next large earthquake to supply fresh recordings. The authors also note that the framework was informed by recent events, including the 2023 moment magnitude 7.8 Kahramanmaras earthquake in Turkey, whose near-fault recordings have become an important test case for pulse identification and simulation methods.

Accessibility is another notable feature of the work. The processed dataset, together with MATLAB code for identifying the optimal pulse in near-fault ground motions and for generating the empirical pulse model, has been released publicly through Zenodo, while the raw waveforms remain freely downloadable from the PEER NGA-West2 database. This open approach lowers the barrier for practicing engineers and researchers in seismically active regions to incorporate directivity and fling effects into their hazard and risk calculations. The study also acknowledges insightful discussions with Professor Jack W. Baker of Stanford University regarding pulse types and the functional form of the model, and it was supported by the Ministry of Education, Singapore, under the InVEST program for integrating volcano and earthquake science and technology.

For cities that sit directly above or beside active faults — from Los Angeles and Wellington to Istanbul and Kathmandu — the difference between ordinary shaking and a coherent velocity pulse can be the difference between repairable damage and collapse. By transforming decades of strong-motion recordings into a compact, predictive, and openly available model, this research moves the field closer to hazard assessments that reflect not just how hard the ground will shake, but how it will shake. As computational tools for seismic risk analysis grow more sophisticated, models of this kind provide the physically consistent input that engineers need to design structures capable of withstanding the sharpest blows an earthquake can deliver.

Subject of Research: Empirical modeling of near-fault velocity pulses in earthquake ground motion

Article Title: Empirical pulse model for near-fault ground motion considering magnitude, distance, and site characteristics

Article References: Chen, G., Chian, S. C., Beer, M., & Wei, S. (2026). Empirical pulse model for near-fault ground motion considering magnitude, distance, and site characteristics. Bulletin of Earthquake Engineering. https://doi.org/10.1007/s10518-026-02650-2

Image Credits: AI Generated

DOI: 10.1007/s10518-026-02650-2

Keywords: near-fault ground motion, velocity pulse, pulse-like records, NGA-West2, wavelet transform, seismic hazard, ground motion simulation, rupture directivity, fling-step, Vs30, earthquake engineering, Bulletin of Earthquake Engineering

Prefabricated reinforced concrete construction occupies a distinctive place in structural engineering. Unlike cast-in-place buildings, whose columns and beams are monolithically poured, precast structures are assembled from factory-produced elements joined on site. This makes them fast and economical to build, but it concentrates seismic vulnerability in the connections. In the classic Turkish precast industrial building, roof girders rest on column corbels, typically through dowel bars and elastomeric bearing pads, and the entire lateral load path depends on how well these joints hold together when the ground lurches. The 2023 Kahramanmaraş earthquake sequence, with its pulse-like near-fault motions and unusually high vertical accelerations, tested those joints as severely as any event in Turkish history.

The research team began with field investigations in the affected region, documenting damage patterns across prefabricated buildings exposed to the twin shocks. Their reconnaissance identified a recurring catalogue of construction deficiencies: inadequate dowel detailing at girder-corbel connections, missing elastomeric bearing pads, substandard grout applications, and insufficient confinement reinforcement in columns and joints. Each of these defects, individually modest in appearance, proved capable of triggering or accelerating structural failure. Where bearing pads were absent, girders pounded directly against concrete corbels, crushing the bearing surfaces and losing their ability to accommodate the relative displacements that near-fault shaking imposes. Where dowels were poorly anchored or under-reinforced, the connections that should have tied roof girders to columns simply gave way.

These observations align with a long history of lessons from Turkish earthquakes. Precast structures were damaged in the 1998 Ceyhan earthquake, the 1999 Kocaeli earthquake, the 2011 Van earthquake, and the 2020 Sivrice earthquake, and in each event the same weak points surfaced: connections, corbels, and the detailing that modern codes require but field practice does not always deliver. What distinguishes the new study is that it does not stop at cataloguing damage. It converts the field evidence into quantitative fragility models, the statistical machinery that engineers use to estimate the probability that a structure will exceed a given damage state at a given level of ground shaking intensity.

Fragility analysis works by subjecting numerical models of a structure to suites of ground motion records and tracking how often a governing limit state, such as the onset of significant connection damage or loss of lateral load capacity, is exceeded as shaking intensity increases. The team built detailed nonlinear models of representative reinforced concrete prefabricated buildings and ran them through ground motions representative of the Kahramanmaraş sequence, including records with the velocity pulses and strong vertical components characteristic of near-fault sites. The resulting fragility curves provide a probabilistic portrait of vulnerability, allowing engineers to compare design variants on a common, defensible footing rather than relying on anecdote alone.

The single most striking quantitative finding concerns the roof girder-to-corbel connection. When the dowels connecting girders to columns were bolted, the seismic resilience of the structure improved dramatically: the median ground motion intensity at which the governing limit state was exceeded nearly doubled compared with structures relying on unbolted dowel connections. In practical terms, a building with bolted dowel connections could withstand roughly twice the shaking intensity before reaching its critical damage threshold. That is not an incremental improvement; it is the difference between a structure that survives a near-fault event and one that does not, achieved through a connection detail that costs comparatively little to implement.

The study also examined the role of infill walls, the masonry or precast panels that fill the bays between columns. In general, infill walls improved seismic resistance, stiffening the frames and sharing lateral load that would otherwise concentrate entirely on the columns. But the analysis revealed a crucial caveat: the benefit depended heavily on the integrity of the connections between the walls and the surrounding frame. Where those connections were robust, the walls acted as effective seismic fuses and load-sharing elements. Where the connections were poor, the walls detached early, their contribution vanished, and in some scenarios the falling panels introduced additional hazards. The lesson is that infill walls are not a passive benefit that can be assumed; they are only as good as the detailing that ties them into the structural system.

Near-fault effects emerged as a decisive amplifier of all these vulnerabilities. Earthquakes that rupture directly beneath or very close to a site produce ground motions with forward directivity, meaning a long-period velocity pulse arrives with much of the fault’s slip concentrated in a single large cycle of motion. The Kahramanmaraş events, including documented episodes of supershear rupture, delivered exactly this kind of pulse-like loading, along with vertical accelerations strong enough to degrade the friction and bearing capacity of simply supported precast elements. For connections already weakened by missing pads or deficient dowels, the combination of horizontal pulses and vertical acceleration was punishing. The study’s numerical results make clear that fragility assessments for precast buildings in near-fault zones must explicitly account for these motion characteristics rather than relying on generic record sets.

From these findings the authors draw a clear retrofitting agenda for the existing stock of reinforced concrete prefabricated structures. Priority measures include upgrading connection details, particularly bolting dowel connections at girder-corbel joints; adding elastomeric bearing pads where they are missing; and installing properly designed precast infill walls with reliable connections. Beyond the physical interventions, the study emphasizes the need for clear design guidelines and rigorous field assessment protocols so that existing buildings, especially in regions exposed to near-fault seismicity, can be systematically evaluated and reinforced before the next earthquake rather than after. The authors note that implementing these strategies would substantially enhance the seismic resilience of the precast building stock, reducing potential future human and economic losses.

The broader significance of the work extends beyond Türkiye. Precast industrial construction is common across seismic regions worldwide, from the Mediterranean to the Americas, and the failure modes documented after Kahramanmaraş echo those observed after the 2012 Emilia earthquakes in Italy, the 1994 Northridge earthquake in California, and the 1995 Kobe earthquake in Japan. The Turkish study adds a quantitative dimension to that international record, demonstrating with fragility curves just how much performance hinges on a handful of connection details. For engineers, the message is disarmingly simple: in prefabricated construction, the earthquake finds the joints. Bolting a dowel, seating a bearing pad, or grouting a connection properly may look like minor line items in a construction budget, but the difference they make, roughly a doubling of the shaking a building can survive, is the kind of margin on which lives and livelihoods depend when the fault finally slips.

Subject of Research: Seismic fragility and construction deficiencies of reinforced concrete prefabricated buildings in the 2023 Kahramanmaraş earthquakes

Article Title: Seismic performance assessment of reinforced concrete prefabricated structures during the 2023 Kahramanmaraş earthquakes: fragility analysis and construction deficiency evaluation

Article References: Seismic performance assessment of reinforced concrete prefabricated structures during the 2023 Kahramanmaraş earthquakes: fragility analysis and construction deficiency evaluation. (n.d.). https://doi.org/10.1007/s10518-026-02712-5

Image Credits: AI Generated

DOI: 10.1007/s10518-026-02712-5

Keywords: prefabricated concrete, Kahramanmaraş earthquakes, fragility analysis, seismic performance, dowel connections, corbel connection, elastomeric bearing pads, infill walls, near-fault ground motion, retrofitting, East Anatolian Fault, Bulletin of Earthquake Engineering