Yih-Min Wu

This study examines the relationship between operational ground-motion parameters and building damage during the 2016 M _w 6.4 Meinong earthquake in southern Taiwan. We integrate strong-motion recordings from 599 Taiwan Strong Motion Instrumentation Program (TSMIP) stations with a manually verified, georeferenced dataset of 626 damaged buildings, including 271 red-tagged and 355 yellow-tagged buildings in Tainan City. The analysis was conducted at the administrative-district level by comparing district-level damage rates with interval-based peak ground acceleration (PGA) and peak ground velocity (PGV) estimates. Non-zero district-level damage rates first appeared in the PGA interval of approximately 150–175 gal and the PGV interval of approximately 10–20 cm/s, corresponding to approximately MMI VI–VII. In this interval-averaged district-level analysis, PGA showed a clearer descriptive correspondence with red- and yellow-tagged building damage rates than PGV. Building-story information indicates that approximately 70% of the damaged buildings were low-rise structures, suggesting that the observed PGA correspondence may be related to the predominance of low-rise buildings and short-period shaking in the most heavily damaged areas. The results do not imply that PGA is universally superior to PGV; rather, PGA and PGV should be interpreted as complementary parameters whose relative usefulness depends on building inventory, site conditions, and analytical scale. This work provides a manually verified building damage dataset and an event-specific reference for interpreting rapid shaking maps and seismic impact information under Taiwan’s updated red- and yellow-tagged building classification system.

Local magnitude (M _L ), the earliest magnitude scale developed in southern California, enables rapid earthquake characterization based on observed amplitudes and zero-magnitude reference amplitudes (A ₀ ) derived from local events. However, amplitudes are sensitive to path and site effects, motivating the development of the physically robust moment magnitude (M _W ). Previous studies have demonstrated an approximately 1:1 relationship between M _L and M _W for M _L < 6.5 in southern California. In contrast, M _L in Taiwan systematically overestimates M _W , reflecting distinct regional attenuation characteristics. Although prior work has recalibrated the logA ₀ attenuation model for shallow earthquakes in Taiwan, deep events for focal depth larger than 35 km exhibit even larger overestimation, with an average bias of 0.5 magnitude units. In this study, we investigate deep earthquakes in Taiwan and establish a new depth-dependent logA ₀ attenuation model. A model relying solely on hypocentral distance produces depth-dependent residuals; therefore, a depth term (logD) is incorporated to logA ₀ attenuation model. The final regression model is logA ₀ = 0.097–1.587logR − 0.0014R + 0.417logD ± 0.273, where R is hypocentral distance and D is focal depth. The results demonstrate that logA ₀ attenuation varies systematically with both distance and depth, consistent with Richter’s description that earthquakes at different depths require distinct logA ₀ values. The recalibrated M _L shows no depth dependence and exhibits a stable 1:1 relationship with M _W , with a standard deviation of 0.16. The proposed logA ₀ attenuation model enables rapid and reliable M _L estimation for deep earthquakes in Taiwan, enhancing real-time hazard assessment and reducing magnitude conversion uncertainty in combined earthquake catalogs.

Background: Landslides pose significant risks to lives and infrastructure. This study developed landslide susceptibility mapping (LSM) for Yilan County, Taiwan, a region highly affected by seismic activity and intense rainfall. A comprehensive inventory of 12,047 landslides (2004–2017) and 12 causative factors spanning topography, hydrology, geology, and seismicity were compiled. Three multivariate statistical methods, Analytical Hierarchy Process (AHP), Frequency Ratio (FR), and Simple Additive Weighting (SAW), were applied and validated using Area Under the Curve (AUC) and a suite of error metrics. Results: The dataset was partitioned into 70% training and 30% testing samples. Multicollinearity analysis confirmed that all causative factors (Pearson correlation < 0.7, variance inflation factor < 10) were suitable for inclusion. Chi-square ranking identified slope gradient and annual rainfall as the two most influential factors. The Jenks natural breaks method classified susceptibility into four levels: low, moderate, high, and very high. Validation results showed that AHP achieved the highest AUC (training: 0.830, testing: 0.839), followed by FR (training: 0.828, testing: 0.828) and SAW (training: 0.824, testing: 0.814). AHP also yielded the lowest error values (mean squared error = 1.7 × 10 ⁻³ , root mean square = 2.7 × 10 ⁻² ) and the highest correlation coefficient ( r = 0.9974). Although differences among methods were relatively small (maximum AUC difference of 0.025), AHP consistently outperformed the others across all metrics. High and very high susceptibility zones, comprising approximately 37.5–49.5% of the study area depending on the method, were concentrated in southern Yilan, particularly in Tiansongpi Township, where steep slopes exceeding 30° coincide with annual precipitation of 3100–4700 mm. Conclusions: This framework provides a practical and reproducible approach for landslide hazard assessment and risk management in similar geological settings worldwide.

This study examines the relationship between ground motion parameters and building damage during the 2016 Mw 6.4 Meinong earthquake in southern Taiwan. We integrate strong-motion recordings from 599 Taiwan Strong Motion Instrumentation Program (TSMIP) stations with a georeferenced dataset of 626 damaged buildings (271 red-tagged, 355 yellow-tagged) in Tainan City. Results show that structural damage began at thresholds of ~150-175 gal for peak ground acceleration (PGA) and ~10-20 cm/s for peak ground velocity (PGV). Regression analysis indicates that PGA correlates much more strongly with building damage (r = 0.98 for red-tagged, 0.81 for yellow-tagged) than PGV (r = 0.46 and 0.26). About 70% of damaged buildings were low-rise (1-3 stories), consistent with resonance effects from short-period ground motions. Local soil liquefaction further contributed to failures in some areas with modest PGV. These findings highlight the dominant role of PGA in assessing low-rise building vulnerability, while PGV remains relevant for high-rise damage. We conclude that both parameters should be jointly considered in seismic impact assessments. This work provides the first quantitative validation of PGA and PGV against Taiwan’s updated red/yellow-tagged building damage classification, establishing a benchmark for future risk evaluation.

The Local Magnitude (ML), was the earliest proposed magnitude scale, allows for rapid determination based on observed amplitudes and a zero magnitude reference amplitudes (A0) derived from local events. However, the amplitudes are susceptible to external factors, the physically robust Moment Magnitude (Mw) was proposed. The previous studies showed a 1:1 relationship between ML and Mw for ML < 6.5 in Southern California; however, ML in Taiwan tend to overestimate when compare to Mw due to different regional attenuation characteristics. Although the previous study has recalibrated the logA0 attenuation model for shallow earthquakes in Taiwan, deep events exhibit an even more significant overestimation, averaging overestimate 0.528. Therefore, this study aims to discuss deep earthquakes in the Taiwan and establish a new logA0 attenuation model for deep events. Since models relying solely on hypocentral distance (R) result in depth-dependent residuals, a depth term (D) was incorporated to account for the physical characteristic of deep seismic waves often propagating through high-Q plates. The derived regression model is:logA0 = 0.097 - 1.587logR - 0.0014R + 0.417logD ± 0.273The results demonstrate that logA0 attenuation varies distinctly with distance at different depths, aligning with Richter mentioned that different depth events require distinct calibration. Furthermore, the logA0 value at a hypocentral distance 100 km differs from that of shallow event models, indicating the difference in attenuation properties. The recalibrated ML demonstrates no depth dependency and a consistent 1:1 relationship with Mw, with a standard deviation ±0.160. This study proposed model provides a rapid and precise ML calculation. This new model enhances the reliability of real-time hazard assessment and reduces magnitude conversion errors in catalog combination.

Syn‐to late‐orogenic extension caused by gravitational collapse is a process that has been documented in most orogens. In this paper, we investigate the contemporaneous stress field in Taiwan to examine syn‐orogenic extensional faulting and the possible gravitational collapse modes by which it is taking place. We use a new, large, well‐constrained, clustered earthquake focal mechanism data set from which we calculate the stress field ( σ ₁ , σ ₂ , σ ₃ ), the direction of the maximum compressive horizontal stress ( S _H ), and determine the most likely fault plane orientations and kinematics. Our results show that, in the upper 21 km of the crust, shearing, with lesser compression are the dominant stress regimes in the Western Foothills and Hsuehshan Range, resulting in a complex interaction of strike‐slip (with transpression and transtension) and thrust faulting. Extension is predominately localized in the upper 14 km of the crust in the Central Range (CR), where it is roughly orogen‐parallel. S _H and the best‐fit fault planes in the CR strike roughly NW‐SE, at a high angle to the structural and topographic grain. At depths greater than 21 km, compression and shear, with transpression and minor extension are the dominant stress regimes throughout Taiwan. Along the eastern flank of the mountain belt, mixed compression and shear stress regimes at depths greater than 50 km are related to the Manila and Ryukyu subduction zones. Our new results allow, for the first time, to characterize an ongoing, large‐scale, orogen‐parallel extension in Taiwan related to lateral extrusion with free‐boundary gravitational collapse.