Determination of earthquake prone zones at university of tadulako based on dominant periods and peak ground acceleration (PGA)

University of Tadulako is the largest State University in Palu City. When an earthquake with a magnitude of 7.4 Mw on September 28, 2018, occurred, many buildings were damaged and even collapsed at that time, even causing casualties due to the rubble. Research on the Local Site Effect is essential for the assessment of seismic hazard. In this study, the local site effect was analyzed using the HVSR method based on microtremor data. The predominant Period (To) ranges between 1.709 s to 3.816 s, indicates that this area consists of alluvium and has a very thick sediment layer. Another parameter calculated in this paper is the peak ground acceleration (PGA) with values from 0.914 g to 0.924 g. This value is the first indicated soil damage level due to ground motions. The results of this study can be used as a consideration in the development of regional spatial planning and building structures based on earthquake analysis.

Ergodic site response model for subduction zone regions

We present an ergodic site response model with regional adjustments for use with subduction zone ground-motion models. The model predicts site amplification of peak ground acceleration, peak ground velocity, and 5% damped pseudo-spectral accelerations of the orientation-independent horizonal component for oscillator periods from 0.01 to 10 s. The model depends on the time-averaged shear-wave velocity in the upper 30 m ( VS30), basin depth, and region and is independent of subduction earthquake type. It has three components: a linear site-amplification term in the form of VS30-scaling, a nonlinear term that depends on VS30 and shaking intensity parameterized by peak ground acceleration at the reference-rock velocity condition of 760 m/s, and a basin sediment-depth term for Japan and Cascadia conditioned on the depth to the 2.5 km/s shear-wave velocity isosurface ( Z2.5). A global VS30-scaling model is provided along with regional adjustments for Japan, Taiwan, South America, Alaska, and Cascadia. The nonlinear model is global, with a functional form that has often been used to fit nonlinear responses inferred from simulations, but here we calibrate it empirically. Relative to a prior model for shallow earthquakes in active tectonic regions, our subduction zone global VS30-scaling is comparable at short periods (<1.0 s) but weaker at long periods, while the nonlinear site response is generally less pronounced but extends to lower levels of shaking. Basin depth models are conditioned on the difference of the actual Z2.5 and a VS30-conditioned mean Z2.5. Sites with positive differential depths have increased long-period site responses and decreased short-period responses, with the opposite occurring for negative differential depths.

Mobile home fragility curves

Seismic fragility of mobile (manufactured) homes is investigated. Compiled is a catalog of home performance in past earthquakes. Intensity measures causing damage are characterized by peak ground acceleration and velocity. Damage is defined as when the home is knocked out of position necessitating repairs and re-installation. Four categories of support conditions are identified: unanchored, tie-downs, proprietary systems, and perimeter wall foundations. Suggested fragility curves for unanchored homes and homes with tie-downs are derived from computer simulations. As a benchmark, a fragility curve for proprietary and perimeter wall systems is taken as the same as that for conventional wood homes. Shortcomings of using tie-down and proprietary systems in high seismic zones are discussed. The suggested fragility curves account for the different categories of support conditions thereby representing advancement to those in the Hazus national standardized risk modeling methodology.

The Comparison of Spatial Models in Peak Ground Acceleration (PGA) Study

This study was conducted to compare the performance of three different spatial analysis models: Inverse Distance Weighted (IDW), Ordinary Kriging,­­ and Regularized Spline interpolation technique to determine the best fit model representing Peak Ground Acceleration (PGA) in West Java Province, Indonesia. The three models are commonly used in spatial visualization, but have different calculation methods. The calculations were performed using available formulas while the spatial modeling was conducted using the algorithms in GIS software. Meanwhile, the accuracy of the spatial model and factual calculation was determined through the Root Mean Square Error (RMSE). The results showed differences for both spatial distribution and maximum and minimum values for each model. However, IDW was observed to be the model which approaches the factual value of the PGA calculation as indicated by its RMSE value of 0.772352 in comparison with the 7.169879 (Ordinary Kriging) and 1.140802 (Regularized Spline).

Relationships between macroseismic intensity and peak ground acceleration and velocity for the Vrancea (Romania) subcrustal earthquakes

The goal of this paper is to develop a new empirical relationship between observed macroseismic intensity and strong ground motion parameters such as peak ground acceleration (PGA) and velocity (PGV) for the Vrancea subcrustal earthquakes. The recent subcrustal earthquakes provide valuable data to examine these relationships for Vrancea seismogenic region. This region is one of the most active seismic zones in Europe and it is well-known for the strong subcrustal earthquakes. We examine the correlation between the strong ground-motion records and the observed intensities for major and moderate earthquakes with Mw ≥ 5.4 and epicentral intensity in the range VI to IX MSK degrees that occurred in Vrancea zone in the period 1977-2009. The empirical relationships between maximum intensity and ground parameters obtained and published by various authors have shown that these parameters do not always show a one-to-one correspondence, and the errors associated with the intensity estimation from PGA/PGV are sometimes +/-2 MSK degree. In the present study, the relation between macroseismic intensity and PGA/PGV will be given both as a mathematical equation, but also as corresponding ground motion intervals. Because of the intensity data spreading and errors related to mathematical approximations, it is necessary to systematically monitor not only the acceleration and velocity but also all the other ground motion parameters. The mathematical relation between these parameters might be used for the rapid assessment of ground shaking severity and potential damages in the areas affected by the Vrancea earthquakes.

Seismic and Structural Analyses of the Eastern Anatolian Region (Turkey) Using Different Probabilities of Exceedance

Seismic hazard analysis of the earthquake-prone Eastern Anatolian Region (Turkey) has become more important due to its growing strategic importance as a global energy corridor. Most of the cities in that region have experienced the loss of life and property due to significant earthquakes. Thus, in this study, we attempted to estimate the seismic hazard in that region. Seismic moment variations were obtained using different types of earthquake magnitudes such as Mw, Ms, and Mb. The earthquake parameters were also determined for all provincial centers using the earthquake ground motion levels with some probabilities of exceedance. The spectral acceleration coefficients were compared based on the current and previous seismic design codes of the country. Additionally, structural analyses were performed using different earthquake ground motion levels for the Bingöl province, which has the highest peak ground acceleration values for a sample reinforced concrete building. The highest seismic moment variations were found between the Van and Hakkari provinces. The findings also showed that the peak ground acceleration values varied between 0.2–0.7 g for earthquakes, with a repetition period of 475 years. A comparison of the probabilistic seismic hazard curves of the Bingöl province with the well-known attenuation relationships showed that the current seismic design code indicates a higher earthquake risk than most of the others.

Evaluation of potential liquefaction based on Cone Penetration Test (CPT) data

An earthquake can inflict a liquefaction hazards which can damage buildings and infrastructure. Furthermore, earthquakes are difficult to predict when and where earthquakes will occur and happen suddenly without being preceded by signs. Therefore, we must do a geological investigation before building a construction to evaluate the potential liquefaction in that area. Evaluation of the potential liquefaction using Cone Penetration Test (CPT) is one method can be used because repeatable, provided a continuous profile, and economic. This method needs peak ground acceleration (amax) value at an interval of 0.1 g to 0.6 g and earthquake magnitude of 6.2 scale richter. Based on the results of the research was obtained in this research area, there were potential liquefactions when the peak ground acceleration (amax) value was above 0.3 g.

Risk-adjusted Design Basis Earthquake’s Adequacy for use in Seismic Design Codes

In most buildings’ seismic design codes design basis peak ground acceleration (PGADBE) is provided by employing a uniform-hazard approach. However, a new trend in updating seismic codes is to adopt a risk-informed method to estimate the PGADBE so-called risk-adjusted design basis peak ground acceleration (PGARDBE). An attempt is made here to examine the adequacy of the PGARDBE to fulfill the assumptions made in seismic codes for converting the maximum considered earthquake’s (MCE) intensity to PGADBE. To this end, the performance of regular intermediate steel moment frames (IMF) is assessed in terms of collapse margin (CMR) and residual drift ratios in the event of MCE and design basis earthquake (DBE), respectively. The PGARDBEs are computed for Karaj County, Iran. A set of 96 index archetypes of regular IMF are designed considering four design parameters, which include the number of stories (2, 3, 6, 9, 12, and 15), span lengths (4 and 8 meters), occupancies (residential and commercial), and seismic demands (0.15, 0.25, 0.35 and 0.45g). The PGADBE prescribed by Standard No. 2800 for Karaj neither meets the assumed acceptance criteria nor stands on the safe side. Meanwhile, PGARDBE fulfills the acceptance criteria but does not necessarily satisfy the implicit assumption made in codes that the code-conforming buildings have at least a CMR of 1.5 if the MCE occurs. This emphasizes that the PGARDBE should not be used without examining the CMR fulfillment. The results recommend that a lower limit need to be set on PGARDBEs, which is found to be 0.35g for Karaj. Outcomes also reveal that the code-conforming buildings designed with the proposed PGARDBE can fulfill both repairability and life safety performances at the DBE and MCE, respectively. These buildings also have a high chance to be even considered as repairable ones at the seismic demand of MCE. Furthermore, regardless of the employed method for estimating PGADBE, various relationships between design parameters with different performance indicators such as CMR, residual drift ratio, ductility demand, imposed drift ratio, and building’s normalized weight are presented. These relationships can be used to evaluate the buildings’ safety factor against collapse and repairability, justification of using IMF in regions with high seismicity, level of structural and nonstructural damage as well as the economic consequence of changes in PGADBE. The presented relationships provide a multi-criteria decision-making tool to decide on the optimum PGADBE leading to an affordable alternative and tolerable damage.

Estimation of Peak Ground Acceleration (PGA) and Spectral Acceleration (Sa) Vertical Component for Interface Subduction Zone Earthquakes of North-east India (NEI) and Adjacent Regions

This article presented ground motion model (GMM) for vertical peak ground acceleration (PGA) and pseudo spectral acceleration (Sa) at 5 % damping for North-east India (NEI) and adjacent regions at a time period of 0.01 to 5 s, and hypocentral distance 40 to 300 km. We used combined point source (4.5 ≤ Mw ≤ 6.5) and finite fault model (6.5 < Mw ≤ 9.5) (refer as combined model) to develop GMM for vertical component of ground motion (VCGM) for the region. The vertical GMM obtained is validated with the available recorded events in NEI and adjacent regions for the interface subduction zone earthquakes. It is observed that peak ground accelerations and spectral accelerations are 55 to 65% lesser than the horizontal components of ground motions. VCGM parameters obtained in this study play an important role in designing low rise buildings and linear superstructures such as bridges, silos and chimneys.