Development of new attenuation equation for subduction mechanisms in Malaysia water

The attenuation equation for far field earthquake is important because the earthquake occurring in neighboring countries can be felt in Malaysia. In this study, a new attenuation was generated using the regression method. It was developed to calculate the peak ground acceleration (PGA) onsite (offshore platform). The database consisting of more than 150 PGAs from 9 events of earthquakes recorded by the Seismology Station in Malaysia was used to develop the relationship. In addition, attenuation relationships for subduction mechanisms from previous researchers are then compared with the newly generated ones in this research. The new attenuation equation was also validated and used to calculate the acceleration for far field earthquake in a case study of offshore platform at a Terengganu seaside. The result of PGA from the new generated attenuation relationship was in a good match with previous attenuation equations.     

Attenuation relations of peak ground acceleration and velocity in the Southern Dead Sea Transform region

Using the recorded earthquake strong ground motion, the attenuation of peak ground acceleration (PGA) and peak ground velocity (PGV) are derived in the southern Dead Sea Transform region. The expected values of strong motion parameters from future earthquakes are estimated from attenuation equations, which are determined by regression analysis on real accelerograms. In this study, the method of Joyner and Boor [Bull Seismol Soc Am 71(6):2011–2038, 1981] was selected to produce the attenuation model for the southern Dead Sea Transform region. The dataset for PGA consists of 57 recordings from 30 earthquakes and for PGV 26 recordings from 19 earthquakes. The attenuation relations developed in this study are proposed as replacement for former probabilistic relations that have been used for a variety of earthquake engineering applications. The comparison between the derived PGA relations from this study with the former relations clearly shows significant lower values than the other relations.     

Hybrid attenuation model for estimation of peak ground accelerations in the Kutch region, India

The Kutch region of Gujarat in India is the locale of one of the most devastating earthquake of magnitude (M _w) 7.7, which occurred on January 26, 2001. Though, the region is considered as seismically active region, very few strong motion records are available in this region. First part of this paper uses available data of strong motion earthquakes recorded in this region between 2006 and 2008 years to prepare attenuation relation. The developed attenuation relation is further used to prepare synthetic strong motion records of large magnitude earthquakes using semiempirical simulation technique. Semiempirical simulation technique uses attenuation relation to simulate strong ground motion records of any target earthquake. The database of peak ground acceleration obtained from simulated records is used together with database of peak ground acceleration obtained from observed record to develop following hybrid attenuation model of wide applicability in the Kutch region: $$ \begin{aligned} \ln \left( {\text{PGA}} \right) & = - 2.56 + 1.17 \, M_{\text{w}} - \, 0.015R - 0.0001\ln \left( {E + 15} \right) \\ &\quad 3.0 \le M_{\text{w}} \le 8.2;\quad 12 \le R \le 120;\quad {\text{std}} . {\text{ dev}}.(\sigma ): \pm 0.5 \\ \end{aligned} $$ ln ( PGA ) = ? 2.56 + 1.17 M w ? 0.015 R ? 0.0001 ln ( E + 15 ) 3.0 ≤ M w ≤ 8.2 ; 12 ≤ R ≤ 120 ; std . dev . ( σ ) : ± 0.5 In the above equation, PGA is maximum horizontal ground acceleration in gal, M _w is moment magnitude of earthquake, R is hypocentral distance, and E is epicentral distance in km. The standard deviation of residual of error in this relation is 0.5. This relation is compared with other available relations in this region, and it is seen that developed relation gives minimum root mean square error in comparison with observed and calculated peak ground acceleration from same data set. The applicability of developed relation is further checked by testing it with the observed peak ground acceleration from earthquakes of magnitude (M _w), 3.6, 4.0, 4.4, and 7.7, respectively, which are not included in the database used for regression analysis. The comparison demonstrates the efficacy of developed hybrid attenuation model for calculating peak ground acceleration values in the Kutch region.     

http://www.sciencedirect.com/science/article/pii/S1674987114001376

A new model is derived to predict the peak ground acceleration(PGA) utilizing a hybrid method coupling artificial neural network(ANN) and simulated annealing(SA), called SA-ANN. The proposed model relates PGA to earthquake source to site distance, earthquake magnitude, average shear-wave velocity,faulting mechanisms, and focal depth. A database of strong ground-motion recordings of 36 earthquakes,which happened in Iran's tectonic regions, is used to establish the model. For more validity verification,the SA-ANN model is employed to predict the PGA of a part of the database beyond the training data domain. The proposed SA-ANN model is compared with the simple ANN in addition to 10 well-known models proposed in the literature. The proposed model performance is superior to the single ANN and other existing attenuation models. The SA-ANN model is highly correlated to the actual records(R=0.835 and r =0.0908) and it is subsequently converted into a tractable design equation.     

A neural network approach for attenuation relationships: An application using strong ground motion data from Turkey

This paper presents an application of neural network approach for the prediction of peak ground acceleration (PGA) using the strong motion data from Turkey, as a soft computing technique to remove uncertainties in attenuation equations. A training algorithm based on the Fletcher–Reeves conjugate gradient back-propagation was developed and employed for three sample sets of strong ground motion. The input variables in the constructed artificial neural network (ANN) model were the magnitude, the source-to-site distance and the site conditions, and the output was the PGA. The generalization capability of ANN algorithms was tested with the same training data. To demonstrate the authenticity of this approach, the network predictions were compared with the ones from regressions for the corresponding attenuation equations. The results indicated that the fitting between the predicted PGA values by the networks and the observed ones yielded high correlation coefficients (R²). In addition, comparisons of the correlations by the ANN and the regression method showed that the ANN approach performed better than the regression. Even though the developed ANN models suffered from optimal configuration about the generalization capability, they can be conservatively used to well understand the influence of input parameters for the PGA predictions.     

Seismic hazard map of Coimbatore using subsurface fault rupture

This study presents the future seismic hazard map of Coimbatore city, India, by considering rupture phenomenon. Seismotectonic map for Coimbatore has been generated using past earthquakes and seismic sources within 300 km radius around the city. The region experienced a largest earthquake of moment magnitude 6.3 in 1900. Available earthquakes are divided into two categories: one includes events having moment magnitude of 5.0 and above, i.e., damaging earthquakes in the region and the other includes the remaining, i.e., minor earthquakes. Subsurface rupture character of the region has been established by considering the damaging earthquakes and total length of seismic source. Magnitudes of each source are estimated by assuming the subsurface rupture length in terms of percentage of total length of sources and matched with reported earthquake. Estimated magnitudes match well with the reported earthquakes for a RLD of 5.2% of the total length of source. Zone of influence circles is also marked in the seismotectonic map by considering subsurface rupture length of fault associated with these earthquakes. As earthquakes relive strain energy that builds up on faults, it is assumed that all the earthquakes close to damaging earthquake have released the entire strain energy and it would take some time for the rebuilding of strain energy to cause a similar earthquake in the same location/fault. Area free from influence circles has potential for future earthquake, if there is seismogenic source and minor earthquake in the last 20 years. Based on this rupture phenomenon, eight probable locations have been identified and these locations might have the potential for the future earthquakes. Characteristic earthquake moment magnitude (M _w ) of 6.4 is estimated for the seismic study area considering seismic sources close to probable zones and 15% increased regional rupture character. The city is divided into several grid points at spacing of 0.01° and the peak ground acceleration (PGA) due to each probable earthquake is calculated at every grid point in city by using the regional attenuation model. The maximum of all these eight PGAs is taken for each grid point and the final PGA map is arrived. This map is compared to the PGA map developed based on the conventional deterministic seismic hazard analysis (DSHA) approach. The probable future rupture earthquakes gave less PGA than that of DSHA approach. The occurrence of any earthquake may be expected in near future in these eight zones, as these eight places have been experiencing minor earthquakes and are located in well-defined seismogenic sources.     

The first peak ground motion attenuation relationships for North of Vietnam

The first attenuation relationships of peak ground acceleration (PGA) and peak ground velocity (PGV) for northern Vietnam are obtained in this study. Ground motion data are collected by a portable broadband seismic network in northern Vietnam as a part of cooperation between the Institute of Geophysics, Vietnamese Academy of Science and Technology, Vietnam and Institute of Earth Sciences, Academia Sinica, Taiwan. The database comprises a total of 330 amplitude records by 14 broadband stations from 53 shallow earthquakes, which were occurred in and around northern Vietnam in the period between 01/2006 and 12/2009. These earthquakes are of local magnitudes between 1.6 and 4.6, focal depths less than 30 km, and epicentral distances less than 500 km. The new attenuation relationships for PGA and PGV are:

log₁₀(PGA)=-0.987+0.7521M_L-log₁₀(R)-0.00475R,     

Re-evaluations of seismic hazard of Iraq

In recent years, Iraq has experienced an increase in seismic activity, especially, near the east boundary with Iran. Previous studies present their results in terms of PGA and for return periods of 500 years and less, and other studies not continued to include the whole PSHA process whereas some recent studies continued to include the whole PSHA process using earthquakes data till 2009 including dependent events. This study includes two main stages, the first is collecting the earthquakes records including the recent events till the end of March 2016 and applying data processing to get the net catalog to independent events. The second stage is applying the steps of PSHA method. Matlab programs have been built to execute these two stages and to convert the results of PSHA computations into contours of 5% damping PGA and spectral accelerations at 0.2 and 1.0 s for a return period of 2475 years, and for rock sites. Also, spectral acceleration against period has been presented for main cities. Also, the PGA map, for a return period of 475 years, has been plotted and then prepared together with similar maps of neighbor countries in one map for comparison. In general, this comparison indicates the similarity in behavior but, the values reveal a relative agreement and they are between Turkish and Iranian values.     

Characterization of site effects in Montreal,Canada

Recent destructive earthquakes have clearly shown that near-surface geological conditions play a major role in the level of ground shaking in urban areas. In Canada, Montreal is ranked second for seismic risk after Vancouver considering its population and regional seismic hazard. The city is largely built on recent unconsolidated marine and river deposits and most of its infrastructure is old and deteriorated. A seismic risk project that includes a combined methodology for site effects zoning in large cities, using microtremor measurements (H/V method) coupled with 1D numerical modelling (SHAKE91), has been initiated. The experimental approach gives good estimates of the fundamental frequency of soft deposits, while the numerical approach provides good estimates of the soil response in terms of amplification factor related to frequency. Main mechanical properties of soft soils were compiled from various data available, and a sample of input rock motions from real and synthetic earthquakes was used to compute soil response. The influence of marine clays on soil response is significant and is well correlated with thickness of these deposits. PGA amplification factors range from 2 to 4 at frequencies from 2 to 7 Hz, with some occasional larger values. The results demonstrate that the methodology used for our study is both fast and efficient to determine the influence of soft soils in urban environments. Such studies are essential for the effective deployment of seismic instrumentation, land-use planning and seismic mitigation.     

Preliminary seismic hazard maps of Slovenia

The preparation of the preliminary seismic hazard maps of the territory of Slovenia has been based on an expansion of the basic approach laid out by Cornell in 1968. Three seismic source models were prepared. Two of them are based mainly on the earthquake catalogue using the Poissonian probability model. A map of seismic energy release and a map of earthquake epicenter density are used to delineate seismic sources in these models. The geometry of the third model which is based on a rough estimate of seismotectonic setting is taken from the probabilistic seismic hazard analysis of a nuclear power plant in Slovenia. Published ground motion attenuation models based on strong motion records of recent strong earthquakes in Italy are used. Test maps for variable and uniform b-values are presented. The computer program, Seisrisk III, developed by the U.S. Geological Survey is used.     

Global Attenuation Relationship for Estimating Peak Ground Acceleration

Peak Ground Acceleration (PGA) is a very important ground motion parameter which is used to define the degree of ground shaking during an earthquake. It is also very helpful for designing earthquake resistant structure. The PGA can be estimated by attenuation relationships using magnitude, distance, source type etc of a ground motion. In the past, several researchers have developed over 450 attenuation relationships for predicting PGA for a specific region. In the present study an attempt has been made to develop an attenuation relationship on the basis of these available previous relationships in rock site which will be applicable for any region of the world. In the present study, PGA has been expressed as a function of moment magnitude and hypo-central distance in rock site. Chi-square test have also been performed with available earthquake data in American and Indian region for verifying the accuracy of the generated attenuation relationship. Using multiple regression and Genetic Algorithm (GA) the attenuation relationship equations have also been generated. These equations will be very helpful for performing seismic hazard analysis and predicting earthquake force in any region of the world.     

Statistical evaluation of the effect of earthquake with other related factors on landslide susceptibility: using the watershed area of Shihmen reservoir in Taiwan as a case study

Landslide susceptibility evaluation is one of the most important issues in watershed management. After an earthquake, the landslide susceptibility decreases functionally with increases in the distance from the epicenter. Under the same rainfall intensity, landslides are more likely to occur in an area where earthquakes occur more frequently. However, the questions of how much an earthquake should be weighted and how to evaluate the effects of an earthquake still need to be studied. To understand how earthquakes affect rainfall-triggered landslides, the horizontal peak ground acceleration (PGA) data from the Central Weather Bureau Seismic Network is used as the earthquake factor and combined with other factors to determine the weight of earthquakes in landslide susceptibility using logistic regression. The results indicate that the ability of landslide prediction is better when considering the earthquake factor. This study also proved that although there are no co-seismic landslides (after earthquakes) in the study area, the earthquake factor is still required to increase the model accuracy. PGA has been described as a usable factor. In areas with frequent earthquakes and high geological activity, when using historical data to evaluate landslide susceptibility, the earthquake factor should be taken into consideration to prevent errors.     

Strong ground motion attenuation in Aswan area, Egypt

Recent and paleo seismicity indicate that moderate seismic activity is relatively large for Aswan area. This is a warning on the possibility of occurrence of earthquakes in the future too. No strong motion records are available in Aswan area for engineers to rely upon. Consequently, the seismological modeling is an alternative approach till sufficient instrumental records around Aswan become available. In the present study, we have developed new ground motion attenuation relationship for events spanning 4.0?≤? M _w?≤?7.0 and distance to the surface projection of the fault up to 100 km for Aswan based on a statistically simulated seismological model. We generated suites of ground motion time histories using stochastic technique. The ground motion attenuation relation describes the dependence of the strength of the ground motions on the earthquake magnitude and distance from the earthquake. The proposed equation for peak ground acceleration (PGA) for the bed rock is in the form of: $ {\mathbf{log}}{\text{ }}\left( {{\mathbf{PGA}}/{\mathbf{gal}}} \right){\text{ }} = {\mathbf{1}}.{\mathbf{24}} + {\mathbf{0}}.{\mathbf{358}}{M_{\mathbf{w}}} - {\text{ }}{\mathbf{log}}\left( {\mathbf{R}} \right){\text{ }}-{\text{ }}{\mathbf{0}}.{\mathbf{008}}{\text{ }}{\mathbf{R}}{\text{ }} + {\text{ }}{\mathbf{0}}.{\mathbf{22}}{\text{ }}{\mathbf{P}} $ . Where PGA is the peak ground acceleration in gal (cm/s²); M_w, its moment magnitude; R is the closest distance between the rupture projection and the site of interest; and the factor P is a dummy variable. It is observed that attenuation of strong motion in Aswan is correlated with those used before in Egypt.     

用小波变换讨论地震中的多普勒现象

地震中多普勒效应可以确定地震的破裂面等,说明对多普勒效应的研究有实际意义,但目前确定地震中是否存在多普勒效应的方法并不成熟。在研究多普勒效应空间分布规律的基础上,提出用小波变换确定地震中是否存在多普勒效应的方法。选择位于汶川地震断层滑动前方的若干台站对台站最初时段的地震记录进行小波变换时,发现随着震中距的增加,小波谱高频幅值明显大于小波谱低频幅值;说明虽然存在介质对地震波的吸收衰减作用,但多普勒效应的存在仍使得小波谱高频幅值增大。选择与汶川地震断层垂直方位的若干台站对台站最初时段的地震记录进行小波变换时,发现随着震中距的增加,小波谱高频幅值迅速降低,震中距大到一定程度后低频部分的小波谱幅值会明显大于高频部分的小波幅值;说明在该方向上,介质对地震波的高频吸收衰减起主要作用,没有发生多普勒效应。     

Seismic microzonation study in Doon valley, northwest Himalaya, India

Fundamental frequency map of site amplification at different sites in Doon valley, Uttarakhand, India is prepared from microtremor (ground ambient noise) using Horizontal to Vertical Spectral Ratio (HVSR) technique. The fan deposited alluvium filled synclinal valley of Doon lies between Main Boundary Thrust (MFT) and Himalayan Frontal Thrust (HFT) in the Himalayan active seismic belt and experienced many earthquakes in the past. The HVSR at different sites in the Doon valley ranges between the predominant frequencies 0.13 and 12.77 Hz. The HVSR in lower frequencies indicates that the site has either thick sediment covers or less compact rocks with fractures. Based on information on fundamental frequency and soft soil thickness, site classification map is generated. Results indicate that degree of compactness of rock types and presences of sediments vary significantly, which may play a major role in seismic hazard. The use of microtremor, therefore, constitutes an effective and inexpensive approach to site response and soft soil thickness estimation for preliminary microzonation.     

Modeling of strong ground motions for 1991 Uttarkashi, 1999 Chamoli earthquakes, and a hypothetical great earthquake in Garhwal–Kumaun Himalaya

In this study, stochastic finite fault modeling is used to simulate Uttarkashi (1991) and Chamoli (1999) earthquakes using all available source, path, and site parameters available for the region. These two moderate earthquakes are recorded at number of stations of a strong motion network. The predicted peak ground accelerations at these stations are compared with the observed data and the ground motion parameters are constrained. The stress drop of Uttarkashi and Chamoli earthquakes is constrained at 77 and 65?bars, respectively, whereas the quality factor Q _C is 112 $ f^{0.97} $ and 149 $ f^{0.95} $ for these two regions. The high-frequency attenuation parameter Kappa is in the range 0.04?C0.05. The constrained ground motion parameters are then used to simulate Mw 8.5 earthquake in central seismic gap region of Himalaya. Two scenarios are considered with epicenter of future great earthquake at locations of Uttarkashi and Chamoli earthquakes using above constrained parameters. The most vulnerable towns are the towns of Dehradun and Almora where expected PGA is in excess of 600?cm/s² at V_S30 520?m/s when the epicenter of the great earthquake is at the location of Uttarkashi (1991) earthquake. The towns of Shimla and Chandigarh can expect PGA close to 200?cm/s². Whereas when the epicenter of the great earthquake is at the location of Chamoli (1999) earthquake, the towns of Dehradun and Almora can expect PGA of around 500 and 400?cm/s², respectively, at V_S30 620?m/s. The National Capital Region, Delhi can expect accelerations of around 80?cm/s² in both the cases. The PGA contour maps obtained in this study can be used to assess the seismic hazard of the region and identify vulnerable areas in and around central Himalaya from a future great earthquake.     

Seismic hazard studies for Gaziantep city in South Anatolia of Turkey

Seismic hazard studies were conducted for Gaziantep city in the South Anatolia of Turkey. For this purpose, a new attenuation relationship was developed using the data of Zaré and Bard and accelerations were predicted employing this new equation. Deterministic approach, total probability theorem and GIS methodology were all together utilized for the seismic assessments. Seismic hazard maps with 0.25° grid intervals considering the site conditions were produced by the GIS technique. The results indicated that the acceleration values by the GIS hazard modelings were matched with the ones from the deterministic approach, however, they were underestimated comparing with the total probability theorem. In addition, the GIS based seismic hazard maps showed that the current seismic map of Turkey fairly yields conservative acceleration values for the Gaziantep region. Therefore, the constructed GIS hazard models are offered as a base map for a further modification of the current seismic hazard map.     

Probabilistic seismic hazard analysis of Kahramanmaras Province,Turkey

Kahramanmaras and its surroundings are under the influence of East Anatolian and Dead Sea fault zones which have significance in the tectonics of Turkey. The long-term energy accumulation in these zones creates a very high risk level in terms of seismic hazard. In this study, the seismic hazard of Kahramanmaras Province and its vicinity was tried to be determined by using the probabilistic seismic hazard method approach. The earthquake catalog used in the study comprises 424 earthquakes equal or greater than M _w ?=?4.0, covering a time period between 1 January 1900 and 1 January 2015. The earthquake data have been compiled from the catalogs of the International Seismological Center (ISC), Republic of Turkey Prime Ministry Disaster and Emergency Management Precidency (RTPMDEMP), Bogazici University Kandilli Observatory and Earthquake Research Institute. Seismic sources that could affect the study area have been identified according to the Earthquake Model of the Middle East (EMME). Seismic hazard parameters and peak horizontal acceleration values were obtained by using the selected attenuation relationships, and the results were given with iso-acceleration maps corresponding to a recurrence period of 475 years. The calculated peak horizontal acceleration values are generally varying between 0.21 and 0.41 in the study area. The result of this study shows that the southeastern parts of the study area have a greater seismic hazard compared with other parts.     

Comparison Between Recorded and Derived Horizontal Peak Ground Accelerations in Jordan

The isoseismal map for the earthquake that occurred in the Jordan Valley on 11 July 1927 was analyzed and used to develop Peak Ground Acceleration (PGA) Attenuation relation for Jordan needed for use in relevant seismic hazard evaluation procedures. Strong motion data of earthquakes that occurred in Jordan and Israel during the last 15 years were summarized. A comparison is made between recorded PGA's and those calculated using the derived Attenuation relations commonly used by experts in the region. The comparison showed that the derived relation is appropriate for estimating PGA values on alluvium foundations. The derived relation gave results close to those obtained using a relation introduced by Esteva in 1974. The 1982 relation of Ben-Menahem and co-workers gave reasonable predictions of PGA values for most geological formations of foundations, in general.     

Non-Poisson probabilistic seismic hazard assessment

The development of the new seismic hazard map of metropolitan Tehran is based on probabilistic seismic hazard computation using the non-Poisson recurrence time model. For this model, two maps have been prepared to indicate the earthquake hazard of the region in the form of iso-acceleration contour lines. They display the non-Poisson probabilistic estimates of peak ground accelerations over bedrock for 10 and 63 % probability of exceedance in 50 years. To carry out the non-Poisson seismic hazard analysis, appropriate distributions of interoccurrence times of earthquakes were used for the seismotectonic provinces which the study region is located and then the renewal process was applied. In order to calculate the seismic hazard for different return periods in the probabilistic procedure, the study area encompassed by the 49.5–54.5°E longitudes and 34–37°N latitudes was divided into 0.1° intervals generating 1,350 grid points. PGA values for this region are estimated to be 0.30–0.32 and 0.16–0.17 g for 10 and 63 % probability of exceedance, respectively, in 50 years for bedrock condition.