peak ground acceleration

Landslides are defined as the downward movement of a portion of land materials under the direct influence of gravity. Landslides would get triggered by a wide spectrum of initiative factors such as earthquakes as a site effect of that event. In the vicinity of Tehran, significant historical earthquakes have occurred; therefore, tracing them could enhance the Tehran’s historical earthquake catalogue, due to the reason Tehran is a metropolitan and capital of Iran. However, paleoseismology could not determine the magnitude and seismic characteristics of historical earthquakes. Mobarak Abad landslide is a large and historical landslide located on Haraz road, a vital artery connecting Tehran to the Mazandaran Province, and there are significant faults like Mosha, North Alborz, and Khazar in its neighborhood. Hence, it is probable that this landslide occurred due to the generation of dynamic force resulting from an earthquake. Therefore, in this study, the geometrical characteristics of the landslide were measured by field surveying. Then with the empirical equations proposed by various researchers, we estimated the landslide volume and the magnitude of the corresponding earthquake, respectively. In the following, the epicenter and hypocenter of all the historical earthquakes within 200 kilometers of the landslide were identified. Then we utilized some conditions such as Keefer's graphs, error value in epicenter location, and peak ground acceleration to omit earthquakes and identify the corresponding earthquake event. The results demonstrate that two earthquakes of 1830 AD and 855 AD with a maximum acceleration of 0.16g are more probable than the 743 AD earthquake.

Himachal Pradesh state is located in seismically active western Himalayas (India) and its seven districts are in seismic zone V and other in zone IV as per the seismic code of India. Ninety% area of Hamirpur district, the studied area, lies in zone V. Peak ground acceleration (PGA) is one of the most important seismic response parameters in structural seismic design, largely influenced by the sub-soil and input seismic motion characteristics. In the present work, the primary objective is to identify the areas in the district that are prone to amplification of peak ground acceleration and can be delineated for infrastructural planning. Peak ground acceleration is one of the most important parameters used in seismic design of the structures. It is estimated using the computer programme ProShake, wherein the soil parameters from 181 borehole profiles up to 30 m depth and software in-built standard earthquake input motions of magnitude 6.9, 7.0, and 7.2 used as the input parameters. The output peak ground acceleration range from 0.24 g to 0.72 g at the ground surface and from 0.21 g to 0.54 g at a depth of 10 m. There is an attenuation of peak ground acceleration at 30 m depth. The estimation of peak ground acceleration will play an important role in delineating the starta having higher peak ground acceleration amplification. This information can be effectively used for planning of important infrastructure projects like hospitals, educational institutions, and commercial establishments in an economical way in the studied area.

In the present work, the empirical correlations between standard penetration test (SPT) N-values  versus  shear modulus (Gmax), and Peak Ground Acceleration (PGA) amplifications for sub-Himalayan district-Hamirpur, Himachal Pradesh (India) consisting of highly variable soil/rock strata at different depths and across the terrain are evaluated. In the first stage, the N values obtained from SPTs are conducted in the field at 184 locations covering the studied area. The shear wave velocity for each soil profile of each borehole is calculated using the best available correlation in the literature. Further, the seismic response parameters are evaluated for these values using the ProShake software. Finally, the empirical relationships between maximum shear modulus and SPT value for different soil types are determined along with the ground motion amplifications. The amplification factor for Bhoranj sub-division varies from 1.40 to 2.60 and from 1.28 to 2.30, 1.20 to 2.10, 1.22 to 1.85, and 1.22 to 1.70 for Barsar, Nadaun, Hamirpur, and Sujanpur, respectively. The studied area consists of variable soil strata including clay, silt, sand, conglomerate, sandstone, and mixture thereof. The correlation between shear modulus and N value is coherent with already reported correlations for regular soils. The amplification factor reported for the sites plays an important role in planning infrastructure in the region. The correlations between maximum shear modulus (Gmax) and SPT value for hilly terrain comprising of highly complex geological formations such as mixed soil and fractured rocks presented in the study are not available in the research work carried out earlier.

Reinforced concrete tall building failure, in residual areas, can cause catastrophic disaster if they can’t survive during the destructive earthquakes. Hence, determining the damage of these buildings in the earthquake and detecting the probable mechanism formation are necessary for insurance purposes in urban areas. This paper aims to determine the failure modes of the moment resisting concrete frames (MRFs) according to the damage of the beam and column.  To achieve this goal, a 15-storey moment resisting reinforced concrete frame is modeled via IDARC software, and nonlinear dynamic time history analysis is performed through 60 seismic accelerograms. Then the collapse and non-collapse vectors are constructed obtaining the results of dynamic analysis in both modes. The artificial neural network is used for the classification of the obtained modes. The results show good agreement in failures classes. Hence it is possible to introduce the simple weight factor for frame status identification.

There are two common intensity measures (IM), i.e., the peak ground acceleration (PGA) and the spectral acceleration (Sa), for earthquake waves. PGA is a simple peak value of wave, while Sa considers more complex spectral characteristics. And it is necessary to identify which one is suitable for evaluating the seismic vulnerability of high-speed railway (HSR) bridges rapidly developed in the world. A finite element model of a (48 + 80 + 48)m continuous girder HSR bridge with track structure was built by OpenSEES software, and was calculated via an incremental dynamic analysis using both PGA and Sa. The seismic fragility curves of bridge and track components were developed by comparing the seismic demand and capacity of components. The comparison results, respectively, using PGA and Sa, show that both PGA and Sa are suitable for evaluating the seismic vulnerability of HSR bridges, and the using of PGA obtains more conservative fragility curves. Those severely nonlinear components, such as the sliding layer and the sliding bearings, etc., do not have constant local natural vibration periods and their seismic responses are not sensitive to the spectral characteristics of earthquakes. The dispersion of engineering demand parameters (EDPs) using PGA is larger or less than that using Sa for those severely nonlinear components. However, the dispersion of EDPs using PGA is always larger than that using Sa for those linear or slightly nonlinear components.

Seismic hazard assessment like many other issues in seismology is a complicated problem, which is due to a variety of parameters affecting the occurrence of an earthquake. Uncertainty, which is a result of vagueness and incompleteness of the data, should be considered in a rational way. Using fuzzy method makes it possible to allow for uncertainties to be considered. Fuzzy inference system, is used since the study based on uncertainty estimation of seismic hazard for the region Qom, is done. First, the input parameters required for Seismic hazard assessment is fuzzified by fuzzification (in Matlab fuzzy tool-box) and the membership functions are used to set the degree of membership. The inference engine produces fuzzified sets using the output from the fuzzification stage and the rule base engine. The fuzzified sets are then defuzzified using the center of the area. Eventually, using a set of attained coordinates for the Holy Shrine (Masoumeh) a deterministic estimation of seismic hazard is made using both the usual deterministic approaches and the Mamdani fuzzy Inference System. Our results show a peak ground acceleration value of 0.43g using fuzzy inference system.

In the present study, two new hybrid approaches are proposed for predicting peak ground acceleration (PGA) parameter. The proposed approaches are based on the combinations of Adaptive Neuro-Fuzzy System (ANFIS) with Genetic Algorithm (GA), and with Particle Swarm Optimization (PSO). In these approaches, the PSO and GA algorithms are employed to enhance the accuracy of ANFIS model. To develop hybrid models, a comprehensive database from Pacific Earthquake Engineering Research Center (PEER) are used to train and test the proposed models. Earthquake magnitude, earthquake source to site distance, average shear-wave velocity, and faulting mechanisms are used as predictive parameters. The performances of developed hybrid models (PSO-ANFIS-PSO and GA-ANFIS-GA) are compared with the ANFIS model and also the most common soft computing approaches available in the literature. According to the obtained results, three developed models can be effectively used to predict the PGA parameter, but the comparison of models shows that the PSO-ANFIS–PSO model provides better results.

One of the serious damages of tremendous earthquakes is the damage to bridges as the major components in an arterial road network, as relief operation is interrupted following cutting roads. Regardless of the magnitude and severity of an earthquake, other factors are also important in the strength and seismic performance of concrete bridges. Freezing-thawing cycles are among the factors, which erode the piers of concrete bridges over time. Therefore, it is necessary to evaluate the seismic vulnerability of bridges for future designs.
This research aims at discussing the effect of freeze-thaw cycles on the seismic performance of concrete bridges using fragility curves. Fragility curves express the conditional probability to reach or exceed a level of damage as a function of ground motion parameters. The curves have been developed analytically using a probabilistic method. Ground motion parameter, peak ground acceleration, structural criterion, and relative displacement of piles were considered. The non-linear time history analysis in OpenSees was used for demand determination. The curves were drawn for the slight, moderate, and extensive damage levels in two modes of before and after damage caused by thawing and freezing, i.e. the mode in which the compressive strength of column section expose reduced. With respect to the fragility curves, the strength reduction increases bridge vulnerability, especially on slight damage levels. Comparing with the cyclic curves of the most vulnerable column in two modes of before and after the damage showed that energy absorption capacity lowered with the expose compressive strength reducing.

In the present study two popular approaches for the seismic fragility evaluation of RC buildings are considered. First approach is based on series of time history analysis and a power law representing probabilistic seismic demand model. Second approach is based on Incremental Dynamics Analysis to determine the median collapse intensity measure. The two methods are formulated with different assumptions and methodologies for evaluations. The fragility curves and reliability indices are developed for a typical four storeyed frame by both the approaches and a comparison study is performed. The both methods yield almost the same results at same total dispersions.

During January – December 2012 more than 1341 records were recovered from permanent Iran strong motion stations operated by the Road, Housing and Urban Development Research Center. Accelerograms were recovered from ISMN triggered by 634 earthquakes in the magnitude 2.0 to 6.4 ranges. Peak ground acceleration was recorded in Chaykandi1 station about 607 cm/s2 on September 27th, 2012 earthquake.

During January–December 2011 more than 311 records were recovered from permanent Iran strong motion stations operated by the Road, Housing and Urban Development Research Center. Accelerograms were recovered from ISMN triggered by 199 earthquakes in the magnitude 2.0 to 7.2 ranges. Peak ground acceleration was recorded in Baba Monir station about 299 cm/s2 on March 5th, 2011 earthquake.

After the devastating earthquake of 26 December 2003 in Bam, a discipline was followed to prepare a preliminary site effect microzonation map for the city. Seismic hazard studies for two return periods, geological studies accompanied by geophysical surveys and aftershock and microtremor measurements were carried out to provide site classification and PGA distribution maps. The results of this study show that reasonable agreements exist between the 2475 years PGA distribution map and the damage distribution map for the recent earthquake. The 475 years PGA microzonation maps could also be used as a preliminary useful hint in reconstruction and urban planning of the totally destroyed city.

During this year, 329 accelerograms were recorded by 196 accelerographs, which were triggered by 176 earthquakes with different magnitudes. The Reygan earthquake of 2 th December 2010 in Kerman province was the greatest earthquake in this year that triggered 24 accelerographs. The maximum PGA of about 0.61g was recorded in Koohezar station on August 27, 2010 earthquake.

The main objective of this study is to present new method on the basis of genetic algorithms for attenuation relationship determination of horizontal peak ground acceleration and spectral acceleration. The proposed method employs the optimization capabilities of genetic algorithm to determine the coefficients of attenuation relationships of peak ground and spectral accelerations. This method has been applied to 361 Iranian earthquake records with magnitudes between 4.5 and 7.4 obtained from two seismic zones, namely Zagros and Alborz-Central Iran. The obtained results indicated that the proposed method can be characterized as a powerful tool for prediction horizontal peak ground and spectral accelerations.