Probabilistic Seismic Hazard Assessment of Umnugobi aimag (province), Mongolia

One of the most common ways to represent results of the probabilistic seismic hazard assessments (PSHA) are maps of seismic hazard, which usually show values of Peak Ground Acceleration (PGA) in a region for a return period. A common return period is of 475 years. These types of maps are frequently incorporated in seismic codes, which include the minimum requirements to design new buildings. On the other hand, a sensitivity analysis usually gives us additional information about a procedure or result. For instance, a sensitivity analysis about a PSHA can give us information about what variables considered to compute the seismic hazard have a significant influence on the results of seismic hazard. In the present study, we performed a sensitivity analysis related to the PSHA for Barcelona. This analysis was oriented to identify the influence in the results of seismic hazard of the following variables: a) the relationship magnitude-macroseismic intensity chosen to convert values of macroseismic intensity to magnitudes; b) the beta parameter that was used to define part of the seismicity of a seismic source and; c) the ground motion prediction equation (GMPE) which was used to determine intensities values to different distances from the epicenter of earthquakes. For this purpose, we applied the code R-CRISIS, which is the updated version of CRISIS2015. Therefore, the present study had as an additional objective to test the functionality of the new R-CRISIS from the point of view of users. According to the results of the sensitivity analysis of the PSHA of Barcelona both the GMPE and the relationship magnitude-macroseismic intensity are the two variables that have the greater influence on the results of seismic hazard of the present study. For instance, in some results of seismic hazard for the city of Barcelona the values of PGA (for the same return period) differ between them until 82% depending on if we considered the means values of the PGA values of the GMPE or the mean values plus one standard deviation of the PGA values of the GMPE. Finally, according to our experience in the use of the new R-CRISIS in the present study, we can confirm that it is both a powerful and user-friendly software. R-CRISIS has valuable features, for instance, it allows to consider diverse types of criteria to define the type of seismic source. For example, R-CRISIS allows defining different types of geometries of the seismic sources, and different criteria to define the seismicity of each seismic source. An important feature of R-CRISIS is the fact that it includes a database with numerous GMPE ready to be used to compute seismic hazard. Additionally, R-CRISIS has valuables graphical tools which are very helpful during the following two stages: the assigning data and the analysis of results.

Nagaland, situated in the tectonically active eastern Himalayan region, faces significant seismic hazards due to the ongoing collision between the Indian and Eurasian plates. A lack of localised seismic hazard studies in Nagaland restricts accurate fault and ground motion assessment, impeding earthquake risk mitigation. This study aims to perform a seismic hazard analysis of Nagaland at the district level to assess varying seismic demands across the region for improved building safety and cost-effectiveness. Deterministic Seismic Hazard Assessment (DSHA) and Probabilistic Seismic Hazard Assessment (PSHA) were conducted after collecting fault and earthquake data, estimating seismicity parameters, and selecting an appropriate Ground Motion Prediction Equation (GMPE). Results were presented as controlling sources, seismic hazard curves, Peak Ground Acceleration (PGA) values, and uniform hazard spectra for district headquarters. Additionally, the seismic demand of an L-shaped unsymmetrical building was analysed using sitespecific local spectra and the Indian code response spectra (IS 1893:2016) through pushover analysis. Finally, The results shows that the PGA values range from 0.53–0.96g in the DSHA method, 0.16–0.45g for DBE (Design Basis Earthquake – 10% probability of exceedance in 50 yrs), and 0.3–0.74g for MCE (Maximum Considered Earthquake − 2% probability of exceedance in 50 yrs) recurrence interval in the PSHA method, indicating higher seismic hazard levels in Nagaland than the IS 1893:2016 standards. Chaurachandpur-Mao Fault (CMF), Sylhet, and Dauki Faults are identified as critical seismic sources, with Longleng, Mokokchung, Mon, Phek and Zunheboto districts at the highest risk. The results of this study can be helpful to local authorities in earthquake risk mitigation and disaster management planning in the region.

A probabilistic seismic hazard assessment has been carried out along the continental section of the Cameroon volcanic line (CVL) in West Africa. We compiled a catalogue of local earthquakes from different sources and homogenize the magnitudes to moment magnitude (Mw). The seismicity of the CVL is concentrated around Mount Cameroon the active volcano and diffuse on the rest. Three seismic source zones were identified: one in Mount Cameroun, the second NE of the volcano in the grabens of Kumba-Tombel, and the third seismic source corresponds to West Cameroon horst. The recurrence model is that of Gutenberg and Richter, ZMAP software was used to decluster the catalogue and to determine seismic parameters for each source zone. To calculate the hazard, we choose two ground motion prediction equations, and to account for uncertainties, a logic tree approach was implemented using CRISIS software. We estimated the peak ground acceleration (PGA) for eleven cities spread along the CVL, for return period (RP) 475 and 2475 years. The results show that for RP 475 years, Buea, located at the foot of Mount Cameroon, has a PGA of 10% g. This value decreases as one moves away from Buea. The seismic hazard was also calculated for the period of 0.2s. Uniform hazard spectra for RP 475 and 2475 years are plotted for three cities, each chosen in one of the seismic source zone. For each city and RP, the spectral acceleration increases with the period, up to around 0.1s, and then it decreases as the period increases.

Abstract. We perform a fault-based probabilistic seismic hazard assessment (PSHA) exercise in the Upper Rhine Graben to quantify the relative influence of fault parameters on the hazard at the Fessenheim nuclear power plant site. Specifically, we show that the potentially active faults described in the companion paper (Jomard et al., 2017, hereafter Part 1) are the dominant factor in hazard estimates at the low annual probability of exceedance relevant for the safety assessment of nuclear installations. Geological information documenting the activity of the faults in this region, however, remains sparse, controversial and affected by a high degree of uncertainty. A logic tree approach is thus implemented to explore the epistemic uncertainty and quantify its impact on the seismic hazard estimates. Disaggregation of the peak ground acceleration (PGA) hazard at a 10 000-year return period shows that the Rhine River fault is the main seismic source controlling the hazard level at the site. Sensitivity tests show that the uncertainty on the slip rate of the Rhine River fault is the dominant factor controlling the variability of the seismic hazard level, greater than the epistemic uncertainty due to ground motion prediction equations (GMPEs). Uncertainty on slip rate estimates from 0.04 to 0.1 mm yr−1 results in a 40 to 50 % increase in hazard levels at the 10 000-year target return period. Reducing epistemic uncertainty in future fault-based PSHA studies at this site will thus require (1) performing in-depth field studies to better characterize the seismic potential of the Rhine River fault; (2) complementing GMPEs with more physics-based modelling approaches to better account for the near-field effects of ground motion and (3) improving the modelling of the background seismicity. Indeed, in this exercise, we assume that background earthquakes can only host M < 6. 0 earthquakes. However, this assumption is debatable, since faults that can host M > 6. 0 earthquakes have been recently identified at depth within the Upper Rhine Graben (see Part 1) but are not accounted for in this exercise since their potential activity has not yet been described.

Probabilistic seismic hazard assessments (PSHA) form the basis for calculating seismic loads in most contemporary seismic provisions in building codes around the world. The current building code of Iraq, which was published in 1997, is currently undergoing a significant engineering update. This study was undertaken in order to support the building code update and to satisfy the need in Iraq for a contemporary assessment of seismic hazard in terms of spectral accelerations. Seismic source characterization largely relies on a newly compiled earthquake catalog since sufficiently detailed information is not available on active faulting in the country even though there are numerous known active faults. There is also a lack of locally recorded strong-motion data. As a result, we make use of attenuation tomography studies in the region to compare local attenuation characteristics with that in other parts of the world where ground-motion prediction equations are available for use in PSHA. For most of the country, the attenuation of 1HzLg waves indicates an attenuation rate that is slower than active tectonic regions but faster than stable continental regions. Hence, we use ground-motion prediction equations from active tectonic and stable continental regions, weighted equally. The PSHA results are presented for a 2% chance of being exceeded in 50 years and on a reference ground condition of the National Earthquake Hazards Reduction Program (NEHRP) site class B. The probability level and reference ground conditions were selected to be consistent with the update of Iraq’s building code. The largest hazard, and consequently the design ground motions, is in the northern cities of Sulaymaniyah and Erbil, consistent with the fact that they are the two urban areas closest to major tectonic features to the north and east of Iraq. Additionally, the Badra–Amarah fault zone is a significant contributor to seismic hazard in the country; therefore, urban areas near it exhibit high seismic hazard.

<p>The broader Aegean area is one of the highest seismicity regions in Europe, with almost half of the European seismicity released in this region, often with damaging mainshocks, such as the recent <strong>M</strong>7.0 Samos event. While several Probabilistic Seismic Hazard Assessment (PSHA) studies have been performed for this area, an attempt to quantify the main factors controlling PSHA has not been performed. To study the effect that each input factor (seismic source model, GMPE, seismicity parameters, etc.) has on the seismic hazard calculations, an <strong>OFAT</strong> (One Factor at A Time) analysis has been conducted. For this analysis we considered two standard peak ground motion parameters, PGA and PGV, for a typical PSHA scenario, namely 10% probability of exceedance for a mean return period of 50 years (equivalent to a 476 yr return period). For the analysis the following factors were considered: a) Four (4) seismicity area-type source models for the broader Aegean area (Papazachos, 1990; Papaioannou and Papazachos, 2000; Woessner et al., 2015; Vamvakaris et al., 2016), as well as various uncertainties for the associated G-R seismicity parameters and active fault geometries of each seismic source, b) ten (10) Ground Motion Prediction Equations (GMPEs), which contain four NGA-West2 (Abrahamson et al., 2014; Boore et al., 2014; Campbell and Bozorgnia, 2014; Chiou and Youngs, 2014), two European (Bindi et al., 2011; Cauzzi and Faccioli, 2008) and four “Greek” (Theodulidis and Papazachos, 1992; Skarlatoudis et al., 2003; Danciu and Tselentis, 2007; Chousianitis et al., 2018) equations, as well as a variable number of sigma for each equation and, c) the minimum (Mmin) and maximum (Mmax) source magnitude of each seismic source. Tornado diagrams (Howard, 1988) were generated for 42 selected sites of seismological interest that span the study area, allowing to explore the extent of each factor’s effect on the PSHA results. The sensitivity analysis results suggest that the GMPE selection, as well as uncertainties in the G-R parameters <strong>a</strong> and <strong>b</strong> are the most critical factors, significantly affecting the PGA/PGV levels for all sites. They also reveal a strong correlation of PSHA sensitivity with other seismicity parameters. For example, the employed source model and Mmax play a more critical role for regions of low seismicity, while the least important factor is the selected Mmin. The spatial distribution of the PSHA sensitivity on the various factors considered was also examined through the generation of several maps, exposing regions of high and of low PSHA uncertainty. The results can be efficiently employed by scientists and engineers in order to focus research and application efforts for a targeted uncertainty minimization of the most critical factors (which may not be the same for all sub-regions of the examined Aegean area), as well as to evaluate the reliability and uncertainty of the current PSHA estimates that are employed in seismic design.</p>

Earthquake is a sudden release of energy due to faults. Natural calamities like earthquakes can neither be predicted nor prevented. However, the severity of the damages can be minimized by development of proper infrastructure which includes microzonation studies, appropriate construction procedures and earthquake resistant designs. The earthquake damaging effect depends on the source, path and site conditions. The earthquake ground motion is affected by topography (slope, hill, valley, canyon, ridge and basin effects), groundwater and surface hydrology. The seismic hazard damages are ground shaking, structural damage, retaining structure failures and lifeline hazards. The medium to large earthquake magnitude (< 6) reported in Ethiopia are controlled by the main Ethiopian rift System. The spatial and temporal variation of earthquake ground motion should be addressed using the following systematic methodology. The general approaches used to analyze damage of earthquake ground motions are probabilistic seismic hazard assessment (PSHA), deterministic seismic hazard assessment (DSHA) and dynamic site response analysis. PSHA considers all the scenarios of magnitude, distance and site conditions to estimate the intensity of ground motion distribution. Conversely, DSHA taken into account the worst case scenarios or maximum credible earthquake to estimate the intensity of seismic ground motion distribution. Furthermore, to design critical infrastructures, DSHA is more valuable than PSHA. The DSHA and PSHA ground motion distributions are estimated as a function of earthquake magnitude and distance using ground motion prediction equations (GMPEs) at top of the bedrock. Site response analysis performed to estimate the ground motion distributions at ground surface using dynamic properties of the soils such as shear wave velocity, density, modulus reduction, and material damping curves. Seismic hazard evaluation of Ethiopia shown that (i) amplification is occurred in the main Ethiopian Rift due to thick soil, (ii) the probability of earthquake recurrence due to active fault sources. The situation of active fault is oriented in the N-S direction. Ethiopia is involved in huge infrastructural development (including roads, industrial parks and railways), increasing population and agricultural activity in the main Ethiopian Rift system. In this activity, socio-economic development, earthquake and earthquake-generated ground failures need to be given attention in order to reduce losses from seismic hazards and create safe geo-environment.

Probabilistic Seismic Hazard Assessment (PSHA) was carried out for the administrative region of Attica (Greece). Peak Ground Acceleration (PGA) and Peak Ground Velocity (PGV) values were calculated for return periods of 475 and 950 years for five sub-areas covering the entire region. PGA hazard curves and Uniform Hazard Spectra (UHS) in terms of spectral acceleration (Sa) values were generated for Athens, Methana, and the capitals of each island of Attica (Salamina, Aegina, Poros, Hydra, Spetses, Kythira, and Antikythira). Area sources were adopted from the Euro-Mediterranean Seismic Hazard Model 2013 (ESHM13) and its update, ESHM20, taking into account both crustal and slab tectonic environments. Ground Motion Prediction Equations (GMPEs) proposed for the Greek territory were ranked for PGA and PGV. Each GMPE was reconstructed as a weighted model, accounting for normal and non-normal focal mechanisms for each area source. PGA, PGV, and Sa values were computed using a logic tree, integrating the seismotectonic models as major branches and sub-logic trees, comprised of multiple ranked GMPEs for each area source, as minor branches. The results showed higher seismic hazard values in sub-areas near the Gulf of Corinth and the slab interface, which could indicate a need to revise the active building code in Attica.

BackgroundThere were more than 700 earthquakes with a magnitude of more than 5.0 over the past 100 years in the Special Region of Yogyakarta, Indonesia. Due to the high intensity of seismic activities, it is essential to perform seismic hazard analysis by considering local site effects. Therefore, this study aimed to analyze the peak ground acceleration (PGA) value based on the earthquake scenario of May 27, 2006, with a magnitude of 6.3, which occurred on the eastern side of the Opak Fault.MethodsThe study was conducted in the southern part of the Progo River, the Special Region of Yogyakarta, using 31 boreholes and 18 microtremor measurement points. The analysis was carried out using four methods: Kanai (In: Proceeding of Japan Earthquake Engineering Symposium 1–4, 1966) equation using microtremor data, deterministic equations with Ground Motion Prediction Equations Next Generations Attenuation West 2 (GMPE NGA West 2), Kanno et al (Bull Seismol Soc Am 96:879–897, 2006) attenuation equation, and probabilistic method referring to the Indonesian Seismic code.ResultsResults indicated that the highest value of PGA was obtained using the deterministic GMPE NGA West 2 weighted attenuation equation, which varied from 0.475 to 0.549 g. Meanwhile, Kanno et al (Bull Seismol Soc Am 96:879–897, 2006) attenuation equation resulted in values ranging from 0.266 to 0.394 g. In contrast, PGA values obtained through microtremor measurement resulted in a smaller value, in the range of 0.126–0.214 g. Probabilistic analysis in the study area produces values ranging from 0.373 to 0.450 g.ConclusionThe location on the central side of the Progo River shows a lower PGA value than the other sides. PGA values will tend to be higher at locations near the earthquake source. The low PGA value that resulted from microtremor analysis was due to the consideration of local site effects in determining earthquake parameters in the study area. Determining the seismic hazard analysis method in infrastructure planning requires a comprehensive analysis by considering various parameters, such as the planning and design objectives, the location proximity to earthquake sources, historical seismic conditions, and the presence of the local site effects.

Abstract. Italy is one of the most seismically active countries in Europe. Moderate to strong earthquakes, with magnitudes of up to ∼ 7, have been historically recorded for many active faults. Currently, probabilistic seismic hazard assessments in Italy are mainly based on area source models, in which seismicity is modelled using a number of seismotectonic zones and the occurrence of earthquakes is assumed uniform. However, in the past decade, efforts have increasingly been directed towards using fault sources in seismic hazard models to obtain more detailed and potentially more realistic patterns of ground motion. In our model, we used two categories of earthquake sources. The first involves active faults, and using geological slip rates to quantify the seismic activity rate. We produced an inventory of all fault sources with details of their geometric, kinematic, and energetic properties. The associated parameters were used to compute the total seismic moment rate of each fault. We evaluated the magnitude–frequency distribution (MFD) of each fault source using two models: a characteristic Gaussian model centred at the maximum magnitude and a truncated Gutenberg–Richter model. The second earthquake source category involves grid-point seismicity, with a fixed-radius smoothed approach and a historical catalogue were used to evaluate seismic activity. Under the assumption that deformation is concentrated along faults, we combined the MFD derived from the geometry and slip rates of active faults with the MFD from the spatially smoothed earthquake sources and assumed that the smoothed seismic activity in the vicinity of an active fault gradually decreases by a fault-size-driven factor. Additionally, we computed horizontal peak ground acceleration (PGA) maps for return periods of 475 and 2475 years. Although the ranges and gross spatial distributions of the expected accelerations obtained here are comparable to those obtained through methods involving seismic catalogues and classical zonation models, the spatial pattern of the hazard maps obtained with our model is far more detailed. Our model is characterized by areas that are more hazardous and that correspond to mapped active faults, while previous models yield expected accelerations that are almost uniformly distributed across large regions. In addition, we conducted sensitivity tests to determine the impact on the hazard results of the earthquake rates derived from two MFD models for faults and to determine the relative contributions of faults versus distributed seismic activity. We believe that our model represents advancements in terms of the input data (quantity and quality) and methodology used in the field of fault-based regional seismic hazard modelling in Italy.

Recent earthquakes in the Sichuan Province have contributed to significantly expand the existing ground-motion database for China with new, high-quality ground-motion records. This study investigated the compatibility of ground-motion prediction equations (GMPEs) established by the NGA-West2 project in the US and local GMPEs for China, with respect to magnitude scaling, distance scaling, and site scaling implied by recent Chinese strong-motion data. The NGA-West2 GMPEs for shallow crustal earthquakes in tectonically active regions are considerably more sophisticated than widely used previous models, particularly in China. Using a mixed-effects procedure, the study evaluated event terms (inter-event residuals) and intra-event residuals of Chinese data relative to the NGA-West2 GMPEs. Distance scaling was investigated by examining trends of intra-event residuals with source-to-site distance. Scaling with respect to site conditions was investigated by examining trends of intra-event residuals with soil type. The study also investigated other engineering characteristics of Chinese strong ground motions. In particular, the records were analyzed for evidence of pulse-like forward-directivity effects. The elastic median response spectra of the selected stations were compared to code-mandated design spectra for various mean return periods. Results showed that international and local GMPEs can be applied for seismic hazard analysis in Sichuan with minor modification of the regression coefficients related to the source-to-site distance and soil scaling. Specifically, the Chinese data attenuated faster than implied by the considered GMPEs and the differences were statistically significant in some cases. Near-source, pulse-like ground motions were identified at two recording stations for the 2008 Wenchuan earthquake, possibly implying rupture directivity. The median recorded spectra were consistent with the code-based spectra in terms of amplitude and shape. The new ground-motion data can be used to develop advanced ground-motion models for China and worldwide and, ultimately, for advancing probabilistic seismic hazard assessment (PSHA).

Seismic risk assessment is crucial for mitigation of strong earthquakes’ effects on communities since it offers a comprehensive framework for minimizing damage, casualties, and economic losses. This can be accomplished through designing earthquake-resistant structures, retrofitting the existing buildings, economic resilience, urban planning, and public education. One of the key elements of seismic risk assessment is to estimate the earthquake hazard in the region of interest. The most acceptable way to evaluate the earthquake hazard in a given region is to perform a probabilistic seismic hazard assessment (PSHA). The seismic hazard and risk are highest in southwest Iceland due to the transform faulting near a relatively populated region with all critical infrastructures and lifelines. The South Iceland Seismic Zone (SISZ) is one of the two major transform zones of Iceland where earthquakes take place on an array of short, near vertical, and north-south trending right-lateral strike slip faults, known as the ‘bookshelf fault system’. This bookshelf fault system has been shown to be continuous towards the west along the entire Reykjanes Peninsula Oblique Rift (RPOR). Based on geological and seismological evidence, seismogenic potential is variable in the SISZ-RPOR, with the increasing seismogenic depth from west to east. This results in the maximum magnitudes from ∼5.5 in the westernmost part of the RPOR to ∼7−7.2 in the easternmost part of the SISZ, which agrees with the seismicity and also historical catalogue in southwest Iceland. Recently, a new physics-based finite-fault system model has been developed for the SISZ-RPOR, calibrated to the steady-state relative plate velocity of transcurrent tectonic motions across the zone. This model, which is constrained by historical and instrumental seismicity, accounts for the variability in inter fault distances guided by fault mapping and relative relocations of seismic swarms. Therefore, the resulting model is completely specified in terms of suites of 3D strike-slip faults along with their corresponding annual slip rates, thus fully capturing the salient characteristics of spatially variable maximum magnitudes and zone-specific magnitude frequency distributions (MFDs). These zone-specific MFDs are entirely compatible with the physical constraints, effectively explain the observed Icelandic catalogues and also avoid the bias introduced by the short duration of earthquake catalogues. This model was further used to simulate a synthetic finite-fault earthquake catalogue (FFCAT) for a long-time interval with random locations across the region. This physics-based approach is in stark contrast to conventional PSHA which relies on simplified seismic source models and simplistic statistics of an earthquake catalogue that for each subzone is effectively incomplete, whereas the finite-fault catalogues fully incorporate the first two key elements of PSHA, the seismic source locations along with their activity rates. In this study, we take advantage of a new physics-based FFCAT and carry out a Monte Carlo PSHA (MC-PSHA) for several major cities and towns in Southwest Iceland. In the MC-PSHA, the ground motion intensity measures of interest are predicted from each finite-fault by several GMMs. However, different ground motions predictions by different GMMs have the largest contributions to the overall epistemic uncertainty. To reduce the epistemic uncertainty, therefore, we use different data-driven GMM-ranking methods to reduce subjectivity in the selection process. For inferring the most suitable GMMs, we consider several empirical GMMs developed from local, regional and worldwide data. The ranking results favor the Icelandic Bayesian GMMs and thus the logic tree is populated with six Bayesian GMMs with different functional forms for use in PSHA. The PSHA results of this study are shown in terms of hazard curves at different periods. We conclude that this study avoids the use of limited statistics from observed catalogues and is firmly rooted in a physical finite-fault system of Southwest Iceland.

The Canterbury region of the South Island of New Zealand straddles a wide zone of active earth deformation associated with the oblique continent-continent collision between the Australian and Pacific tectonic plates east of the Alpine fault. The associated ongoing crustal strain is documented by the shallow earthquake activity (at depths of &lt;40 km) and surface deformation expressed by active faulting, folding and ongoing geodetic strain. The level of earth deformation activity (and consequent earthquake hazard) decreases from the northwest to the southeast across the region. Deeper-level subduction related earthquake events are confined to the northernmost parts of the region, beneath Marlborough. To describe the geological setting and seismological activity in the region we have sub-divided the Canterbury region into eight domains that are defined on the basis of structural styles of deformation. These eight domains provide an appropriate geological and seismological context on which seismic hazard assessment can be based. A further, ninth source domain is defined to include the Alpine fault, but lies outside the region. About 90 major active earthquake source faults within and surrounding the Canterbury region are characterised in terms of their type (sense of slip), geometry (fault dimensions and attitude) and activity (slip rates, single event displacements, recurrence intervals, and timing of last rupture). In the more active, northern part of the region strike-slip and oblique strike-slip faults predominate, and recurrence intervals range from 81 to &gt;5,000 years. In the central and southern parts of the region oblique-reverse and reverse/thrust faults predominate, and recurrence intervals typically range from -2,500 to &gt;20,000 years. In this study we also review information on significant historical earthquakes that have impacted on the region (e,g. Christchurch earthquakes 1869 and 1870; North Canterbury 1888; Cheviot 1902; Motunau 1922; Buller 1929; Arthurs Pass 1929 and 1994; and others), and the record of instrumental seismicity. In addition, data from available paleoseismic studies within the region are included; and we also evaluate large potential earthquake sources outside the Canterbury region that are likely to produce significant shaking within the region. The most important of these is the Alpine fault, which we include as a separate source domain in this study. The integrated geological and seismological data base presented in this paper provide the foundation for the probabilistic seismic hazard assessment for the Canterbury region, and this is presented in a following companion paper in this Bulletin (Stirling et al. this volume).

Typical seismic hazard problem lies on determination of ground motion characteristics associated with future earthquakes. Strong ground motion characteristics such as Peak Ground Acceleration (PGA) is important information for engineers in order to provide earthquake resistant building. The Indonesian government has provided update of maps of PGA by released a series official PSHA (Probabilistic Seismic Hazard Assessment) maps in 1978, 2002, 2010 and 2017. On the other hand, the NDSHA (Neo-Deterministic Seismic Hazard Assessment) method has been developed and successfully applied to Sumatra. Because of the availability of numerical PGA data for the official PSHA 2010 and 2017, this paper discusses the comparison of PGA between derived from NDSHA and that of official PSHA updated in 2010 and 2017. The spatial resolution of the PGA digital map of PSHA is 0.01 degree and NDSHA is 0.1 degree. Due to the different resolution, a program and a script are developed to incorporate PSHA data into the NDSHA data points by performing interpolation procedure. The comparison results show the PGA of PSHA 2017 is significantly greater than PGA PSHA 2010. However, the PGA values of the 2017 PSHA map are lower than that of PSHA 2010 such as along the Sumatran fault in Central and South Sumatra. The PGA values estimated by using standard NDSHA with 10 Hz cut-off is higher than those of the computed PGA from PSHA at PE (Probability of Exceeding) of 2% in 50 year for official map released in 2010 and 2017. For comparison with PE of 2% in 50 year, the near field NDSHA gives the PGA value greater than that of the PSHA; and for the far field sources. This means the NDSHA calculation for Sumatra gives reasonable results based on the adopted magnitude distance threshold. This is due to the fact that the standard NDSHA is based on the realistic physical simulation of the seismic wave propagation. The comparison between the PGA computed based on the proposed enhanced version of NDSHA and PSHA shows that the updated version gives the same values at near field and lower values at the far sites; whereas the standard one gives a higher value in NDSHA, which in turn gives a higher PGA value for the near and far field sources.

Major seismic activity in India is concentrated along the Himalayan arc including the western Himalaya. A region in the vicinity of Main Boundary Thrust (MBT) and Main Central Thrust (MCT) bounded by latitude 29 N to 36 N and longitude 73 E to 80 E was considered for the study. Nine Seismogenic Source Zones (SSZ), were identified on the basis of seismicity and the tectonics around it. Seismic hazard parameters were computed for each source zone and return periods were calculated for different magnitude earthquakes. For validation of return periods, seven recent earthquakes were studied. Out of seven earthquakes three earthquakes of magnitude between 5.0 and 6.0 occurred in Kangra SSZ . Two Ground Motion Prediction Equations (GMPE’s) were used to estimate peak ground acceleration (PGA) in the region. PGA in the region was estimated to vary between 0.013 g to 0.315 g for 10% probability of exceedance in 50 years, and between 0.024 g to 0.68 g for 2% probability of exceedance in 50 years. Highest PGA values ≥ 0.31 g were observed in Kangra and Chamba district of Himachal Pradesh. For the Kangra SSZ, a return period of 141 years was estimated for magnitude Mw = 8.0, 44 years for Mw = 7 and 14 years for Mw = 6. Results obtained in the present study were compared with other studies. This hazard analysis study underlines the urgency for carrying out vulnerability analysis to estimate the populations that are at risk to this threat perception, so that appropriate mitigation measures can be put in place.