Rapid Estimation of Earthquake Magnitude and Source Parameters Using Genetic Algorithms

To minimize the impacts of large losses and optimize the emergency response when a large earthquake occurs, an accurate early warning of an earthquake or tsunami is crucial. One important parameter that can provide an accurate early warning is the earthquake’s magnitude. This study proposes a method for estimating the magnitude, and some of the source parameters, of an earthquake using genetic algorithms (GAs). In this study, GAs were used to perform an inversion of Okada’s model from earthquake displacement data. In the first stage of the experiment, the GA was used to inverse the displacement calculated from the forward calculation in Okada’s model. The best performance of the GA was obtained by tuning the hyperparameters to obtain the most functional configuration. In the second stage, the inversion method was tested on GPS time series data from the 2011 Tohoku Oki earthquake. The earthquake’s displacement was first estimated from GPS time series data using a detection and estimation formula from previous research to calculate the permanent displacement value. The proposed method can estimate an earthquake’s magnitude and four source parameters (i.e., length, width, rake, and slip) close to the real values with reasonable accuracy.

A Dynamic Method to Predict the Earthquake-Triggered Sliding Displacement of Slopes

The earthquake-induced permanent displacement is an important index of the potential damage to a slope during an earthquake. The Newmark method assumes that a slope is a rigid-plastic body, and the seismic responses of sliding masses or seismic forces along the slide plane are ignored. The decoupled method considers no relative displacement across the sliding plane, so it overpredicts the seismic response of the sliding mass. Both dynamic and sliding analyses are performed in the coupled method, but when Ts/Tm is large, the results are unconservative. In this paper, a method is proposed to predict the earthquake-triggered sliding displacement of slopes. The proposed method is based on the Newmark rigid method, coupled method, and decoupled method considering both the forces at the sliding interface and the system dynamics under critical conditions. For the flexible system, the displacements are calculated with different stiffness values, and the results show that as the stiffness increases and tends to infinity, the critical acceleration and displacements of the proposed method are close to those of the Newmark method. The proposed method is also compared with the Newmark method with the period ratio Ts/Tm. At small values of Ts/Tm, the flexible system analysis results of the displacement are more conservative than those of the rigid block model; at larger values of Ts/Tm, the rigid block model is more conservative than the flexible system.

A Review of the Methods Calculating the Horizontal Displacement for Modular Reinforced Soil Retaining Walls

Most of the damage to reinforced retaining walls is caused by excessive deformation; however, there is no calculation method for deformation under static and dynamic loads in the design codes of reinforced soil retaining walls. In this paper, by collecting the measured displacement data from four actual projects, four indoor prototype tests and two indoor model tests under a total of 10 static load conditions, and comparing the calculation results with seven theoretical methods, the results show that the FHWA method is more applicable to the permanent displacement prediction of indoor prototype tests and that the CTI method is more applicable to the permanent displacement prediction of actual projects and indoor model tests. Two yield acceleration calculation methods and four permanent displacement calculation formulas were selected to calculate the displacement response of two reinforced soil test models under seismic loads and compared with the measured values, and the results showed that the Ausilio yield acceleration solution method was better. When the input peak acceleration ranges from 0.1 to 0.6 g, the Richards and Elms upper limit method is used, and when the input peak acceleration is 0.6–1.0 g, the Newmark upper limit method can predict the permanent displacement of the retaining wall more accurately.

Thigmomorphogenic Responses of Epiphytic Bromeliads to Mechanical Perturbation

Vascular epiphytes represent almost 10% of all terrestrial plant diversity. Despite their growing sites exposed to frequent extensive storms, nothing is known about how external mechanical perturbations by wind affects epiphytes’ growth and development. Therefore, this study investigated the effect of such mechanical stress on the growth rate and morphology of epiphytes. Juvenile plants of two species of bromeliads, grown in the greenhouse, were subjected to varying degrees of mechanical stress – Permanent displacement, tilting and mechanical flexing. ANOVAs were used to test possible treatment effects on growth, root-shoot ratio, root diameter, and leeward-windward root area ratio. Contrary to previous studies on herbaceous plants, these bromeliads showed little to no change in root and shoot properties in either species. Although the root-shoot ratio increased in disturbed Guzmania lingulata plants (Tukey HSD, p < 0.001), it was not observed in Vriesea sp. Treatment effects on growth were inconsistent: stress effect on growth was significant only in the first three months of the experiment (padj < 0.05) in G. lingulata, while none of the stress treatments resulted in negative growth in Vriesea sp. All disturbed plants showed some degree of curvature on their stems and leaves against the area of stress to obtain an upright position. This was probably related to the maintenance of a functional tank. This study provided quantitative and qualitative data to understand thigmomorphogenic responses of bromeliads to mechanical stress. Future studies could include field surveys to quantify on-site wind stress and the corresponding morphological changes in vascular epiphytes.

Seismic Behavior of Stone Pagoda Structure by Shaking Table Test

In general, the stone pagoda structures with discontinuous surfaces are vulnerable to lateral forces and are severely damaged by earthquakes. After the Gyeongju earthquake in 2016 and the Pohang earthquake in 2017, numerous stone pagoda structures were damaged due to slippage, rotation, and the separation of stacked stone. To evaluate seismic resistance of masonry stone pagoda structures, we analyzed the seismic behavior of stone pagoda structures using the shaking table test. Shaking frequency, permanent displacement, maximum acceleration, rocking, and sliding were assessed. Responses to simulations of the Bingol, Gyeongju, and Pohang earthquakes based on the Korean seismic design standard (KDS 41 17 00) were analyzed for return periods of 1000 and 2400 years. We found that the type of stylobate affected the seismic resistance of the stone pagoda structure. When the stylobates were stiff, seismic energy was transferred from lower to upper regions of the stone pagoda, which mainly resulted in deformation of the upper region. When the stylobates were weak, earthquake energy was absorbed in the lower regions, which was associated with large stylobate deformations. The lower part of the tower body was mainly affected by rocking, because the structural members were slender. The higher part of the stone pagoda was mainly affected by sliding, because the load and contact area decreased with height.

Ambient Seismic Noise and Microseismicity Monitoring of a Prone-To-Fall Quartzite Tower (Ormea, NW Italy)

Remote sensing techniques are leading methodologies for landslide characterization and monitoring. However, they may be limited in highly vegetated areas and do not allow for continuously tracking the evolution to failure in an early warning perspective. Alternative or complementary methods should be designed for potentially unstable sites in these environments. The results of a six-month passive seismic monitoring experiment on a prone-to-fall quartzite tower are here presented. Ambient seismic noise and microseismicity analyses were carried out on the continuously recorded seismic traces to characterize site stability and monitor its possible irreversible and reversible modifications driven by meteorological factors, in comparison with displacement measured on site. No irreversible modifications in the measured seismic parameters (i.e., natural resonance frequencies of the tower, seismic velocity changes, rupture-related microseismic signals) were detected in the monitored period, and no permanent displacement was observed at the tower top. Results highlighted, however, a strong temperature control on these parameters and unusual preferential vibration directions with respect to the literature case studies on nearly 2D rock columns, likely due the tower geometric constraints, as confirmed by 3D numerical modeling. A clear correlation with the tower displacement rate was found in the results, supporting the suitability of passive seismic monitoring systems for site characterization and early waning purposes.