Earthquake Return Period Research Articles

Liquefaction Potential Assessment for the City of Mamuju Sulawesi by using N-SPT based methods

Mamuju is the capital city of West Sulawesi Province which has experienced severe damages along its infrastructures due to Majene Earthquake Mw. 6.2 on January 15th 2021. On that event, liquefaction phenomenon has been found on several places, triggering foundation settlements of buildings. Unfortunately, information on Mamuju’s earthquake hazard is still inadequate, while earthquake hazard assessment is urgently needed. Therefore, this study aims to assess liquefaction potential for the city of Mamuju. Serial geotechnical investigations were undertaken through a number of boreholes and N-SPT measurements. For liquefaction assessment, methods of estimating CRRM=7.5 were used including NCEER (1996), Vancouver Task Force (2007), Chinese Code, Japanese Highway Bridge Code, Shibata (1981), Boulanger & Idriss (2014), Cetin et al. (2004), Seed et al. (1983), Tokimatsu & Yoshimi (1983), and Kokusho et al. (1983), while estimation of CSR, the Simplified method (Seed, 1974) was employed. The results show that the coastal areas in the city has a high level of susceptibility to liquefaction. The liquefaction thickness of the ground would be 8 m deep for a 0.367g seismic acceleration (200 years return period earthquake), and 10 – 16 m for 0.414g seismic acceleration (deterministic Mw 7.0 of Fault Mamuju). Ground settlement induced by liquefaction was computed based on Ishihara & Yoshimi (1992) method. It was found that the ground settlement could be 18 – 50 cm, and 31 – 71 cm for each assumed seismic acceleration. The validity of the method used in this study was examined through the comparation of predictive liquefaction thickness and ground settlement based on the empiric methods with the measured ones in the field.

Performance of The Existing Building Under Earthquake Loads Based on Current Indonesian National Standard

This paper presents the results of an assessment of the existing 5-storey building built in 1980, which aims to determine the level of safety against the most recent standards. The method used is non-destructive testing, collecting planning data in the form of as built drawings and implementation data. The assessment of the existing structure consists of an evaluation of the condition of the material, structural system, and analysis of the structure using the latest load standards. The test results of the existing structural material show that the compressive strength of the concrete still meets the requirements based on SNI-2847-2019. The results of the evaluation of the structure against earthquake loads show that the performance of the structure has a mass participation of 100% and the dynamic base shear force (V) reaches 100% of Vstatic therefore it meets the requirements in SNI 1726-2019. The results of the evaluation of the performance of the structure show that the lateral drift and P-delta effects still meet the requirements of the most recent standards. Horizontal and vertical structural irregularities are found in the existing structural system. The structure's overall performance level (X and Y direction earthquakes) is Damage Control. These results are still permitted for structures with a priority factor (Ie) 1.50, with an earthquake return period of 2500 years.

Force based Design Approach for Seismic Evaluation of Padma Multipurpose Bridge Pier at Different Performance Levels

The Padma Multipurpose Bridge (PMB) is one of the biggest megaprojects of Bangladesh connecting one third of the country with the capital city, Dhaka. The infrastructure is expected to produce considerable uplift on the nation’s transport system, the national and regional economy, employment, household income, and ultimately, poverty reduction. From construction and river management points of view, it is the most difficult and engineering innovation-intenstive project in the world. Hence the Padma Multipurpose Bridge (PMB) required analytical, computational and experimental studies. In this work, a 3D Finite Element (FE) model of the actual PMB containing a single (6x150m) 900m modules has been developed in MIDAS Civil, a commercial computer program for bridges. P-y soil spring model following API guideline has been developed to conform flexible support system of the bridge pier. Following BNBC 2020, the bridge's performance has been evaluated for the 475-year, 975 years, and 2475-year return periods for Service Level, Design Basis and the Maximum Credible Earthquake (MCE), respectively. The forced based design shows that the bridge pier reached only 28% and 36% of its axial and shear capacity respectively for an earthquake return period of 2475 years. On the other hand, the pier has reached a maximum of 41% of its total shear capacity for the same seismic level.

Source parameters and scaling relations for small earthquakes in mainland Gujarat region of Western Deccan Volcanic Province, India

The return period of large earthquakes in intraplate regions is more in comparison to the interplate regions. Also, the intraplate region is less instrumented and hence, these regions are devoid of acceleration time histories of large and great earthquakes. The mainland Gujarat region is one of such intraplate regions for which acceleration time histories are not available, however, is vulnerable for earthquakes of M ∼ 6.0. Simulation is performed in these scenarios and the prerequisite is the knowledge of source parameters and scaling laws. We analyzed the spectra of the P- and S-waves recorded by the stations of Gujarat Seismic Network for the mainland Gujarat region of western Deccan Volcanic Province, India. Additionally, we developed scaling laws based on the obtained source parameters. We analyze 177 digital records from 43 local earthquakes during the period 2007–2016 with a magnitude of Ml = 2.5–4.3, which are located in a distance range of 10–250 km, using Brune’s seismic source model (Brune 1970, 1971). According to our study, the calculated stress drop values do not vary considerably with seismic moment values and are generally between 1 and 100 bar for most of the events. Therefore, the earthquakes in this region adhere to the law of self-similarity. As widely observed for conventional earthquakes, we find an inverse relationship between seismic moment and corner frequency for these events. Based on a linear regression analysis between the assessed seismic moment (M 0) and corner frequency (fc), we developed the scaling relation M 0 f c 3 = 2.29 × 1015. Scaling relations developed here are in agreement with those developed for the nearby Kachchh region and various other seismically active areas around the world. Use of regional scaling is recommended instead of global scaling laws for better estimation of seismic hazard. The source parameters and scaling laws presented here can be used for a variety of applications in mainland Gujarat, including the assessment of seismic hazards and the development of earthquake scenarios.

Assessment of Seismic Loss in Surakarta School Buildings

Surakarta is a relatively small yet is categorized as a densely populated city. There are a lot of types of public buildings, such as hospitals, supermarkets, government infrastructures, and school buildings. The city has more than 1100 school buildings threatened by many potential earthquakes. The possibility of an earthquake hitting Surakarta may be fatal and cause significant losses of buildings. However, studies on seismic hazard of the city are still very rare and need more attention. This paper presents a recent study on the seismic loss assessment of school building in Surakarta. The survey has been conducted by a team to visit, check, record and document all the required information to obtain exposure, combined with the information from google map application, while the seismic hazard analysis was carried out using the event-based stochastic method. An open-source application, OpenQuake, was utilized to assess the seismic loss and the results were presented here. The elaborated analysis is presented concluding that the exposure and vulnerability of school buildings are very important factors to determine a risk of loss. It indicates that the wooden school building contributes a highest risk of loss, whereas the confined masonry ones give a lowest risk. Among the whole sub districts in Surakarta, it is assessed that Laweyan suffers the biggest seismic loss of 2.36 million USD due to 500 years return period earthquake and 5.39 million USD due to 2500 years return period earthquake. These results of this study are valuable information for government in order to overcome disaster mitigation policy of Surakarta.

Development of seismic map for offshore platform design in Indonesia, case study of the North Coast of Java

Indonesia’s design of earthquake-resistant offshore platforms does not yet have specific regulations. The commonly used standard in Indonesia, API RP 2A WSD, does not explicitly state the earthquake return period for offshore structures. A more detailed procedure is described in ISO 19901-2:2004. Two methods are introduced in the standard. First, the simplified method allows the use of earthquake maps with a return period of 1000 years. Second, the detailed method requires a site-specific seismic hazard study to determine the return period of earthquakes. This paper presents the development of seismic hazard maps using a simplified method following ISO 19901-2:2004. The maps are prepared using the probabilistic method with a case study on the North Coast of Java. The results show that the study area falls into seismic zones 1 and 2. The seismic hazard maps can be used for earthquake resistance design for structures with exposure level L2 and L3 based on the seismic risk category following the ISO.

Earthquake Activities along the Sagaing Fault Zone, Central Myanmar: Implications for Fault Segmentation

In this study, the three terms related to the seismic activities of the Sagaing Fault Zone (SFZ), central Myanmar, of the possible maximum magnitude, return period, and probability of exceedance (POE) of an earthquake of given magnitude were evaluated and mapped using an improved earthquake catalog (free of duplicate records, foreshocks, aftershocks and recording artifacts) and implementation of a statistical approach. As a result, the SFZ was separated into five segments with different seismicity levels. The highest hazard level was found for the segment between Myitkyina–Northern Mandalay, with a likely generation of an Mw 6.4–7.2 earthquake in the next 50 years. For the Naypyidaw–Bago segment, the hazard levels were in the comparatively medium range with a magnitude 6.0–7.0 Mw earthquake return period of 20–50 and 100–200 years, respectively. The Offshore Andaman Sea segment of the SFZ was defined to have the lower hazard, with only a 10% or lower POE of a 7.0 Mw earthquake within the next 50 years. Therefore, effective mitigation plans should be prepared for this area and in particular for the region nearby to the Myitkyina–Northern Mandalay segment as the highest earthquake-prone area.

Fragility Curves of RC Bridges in México

Large earthquakes have epicenters on the Pacific Coast of Mexico and many of them are responsible of damages in reinforced concrete (RC) bridges. The Pacific Coast is a highly active seismic zone where most of the strong earthquakes in the country occur. In this region, there are new and old RC bridges subjected to ground motions from interplate and intraplate seismic sources. This study evaluates the seismic vulnerability of ten RC bridges, with typical geometry in Mexico, and two existing bridges located close to the Pacific Coast of Mexico. The group of ten bridges includes two span lengths (20 and 40 m), two pier heights (6 and 10 m) and two substructure types (single and multi-colum piers). The bridges were designed according to the regulation codes used in practice in Mexico, and their seismic capacity (C) was evaluated with pushover analysis. The seismic demand (D) was determined using a group of more than one hundred seismic records from interplate and intraplate seismic sources. The random ratio C/D was used to assess the fragility curves of the bridges using four earthquake return periods. The results showed that the two existing bridges have similar trend of behavior and the fragility curves of the bridge models can predict the expected behavior of multi-column or single-column existing bridges.

New insights into the seismic activity of Damascus fault (Syria): a quantitative analysis

Damascus fault is a remarkable reverse tectonic structure trending directly adjacent to Damascus city, and may possibly represent a significant seismic hazard to the city. In this respect, the present work examines the instrumental seismic activity and establishes an earthquake catalogue covering the period 1995-2012 for this important fault, aiming to identify its contribution to the regional seismic hazard. The quantitative analysis reveals the Damascus fault is characterized by low magnitude earthquakes, which implies that the fault could be considered in quiescence status. The analysis exhibit the b-value of Gutenberg-Richter relationship is estimated to be 0.90 using the least-squares method, which could be compatible with a thrust faulting, such as Damascus fault, regarding the published literature. Also, this value could be reasonable for further interpretations. In addition, the return periods of large earthquakes have been estimated to be very long by extrapolation of the established recurrence relationship. Moreover, the maximum regional earthquake magnitude has been estimated by Kijko's procedure as maximum likelihood estimator. This procedure has predicted the maximum possible earthquake magnitude to be 4.2. Consequently, the seismic quiescence, observed actually along Damascus fault, and the estimated long return period implies that a large earthquake could be still so far away.

Risk assessment of CLT-RC hybrid building: Consideration of earthquake types and aftershocks for Vancouver, British Columbia

Tall-timber buildings using cross-laminated timber (CLT) have become a viable sustainable system. This paper presents seismic vulnerability and risk assessment of a 10-story CLT-reinforced concrete hybrid building. The building is designed for the seismicity of Vancouver, and detailed 3D finite element model is developed in OpenSees. The evaluation is undertaken within a performance-based earthquake engineering framework in which seismic demand limits are defined with respect to the earthquake return periods. Two engineering demand parameters, i.e. maximum inter-story drift ratio in both X and Z directions, as well as their combination are considered. Using 30 mainshock and mainshock-aftershock earthquake records (two horizontal components per record), multiple stripe analysis and cloud analysis are performed, and the corresponding fragility and risk are quantified. In addition efficiency of different intensity measures are considered. The vulnerability and risk assessment results show viability of the hybrid building in high seismic zones.

Earthquake risk assessment of the Opak and Merapi-Merbabu active faults to support mitigation program in Yogyakarta province and its vicinity

Based on historical records, Yogyakarta has a high seismic risk related to the earthquake events along active faults, such as the Opak and Merapi-Merbabu Faults. These faults were responsible for several destructive earthquakes in Yogyakarta City and its vicinity and caused fatalities and building damage in the area, e.g., the 2006 (Mw 6.3) Yogyakarta earthquake and earlier in 1943 and 1867. A previous study shows that the Opak Fault has a geodetic slip-rate of 5 mm/y and a potential magnitude Mw 6.6. In addition, the active Merapi-Merbabu Fault has a geodetic slip-rate of 1 mm/y and a potential magnitude Mw 6.6. We used scaling law relations of earthquake parameters and magnitude scenarios to estimate the recurrence time of each fault based on a kinematic model. Our results estimate that the earthquake return period (Tr) for the Opak Fault (Mw 6.6) is ∼162 years, the maximum intensity is ∼VII-VIII MMI scale, the Peak Ground Acceleration (PGA) is ∼36 % g, and Peak Ground Velocity (PGV) is ∼ 30 cm/s for a 5 km hypocentral depth. In the meantime, the earthquake return period for the Merapi-Merbabu Fault (Mw 6.6) is estimated to be ∼810 years, the maximum intensity is ∼ VI-VII MMI, the PGA is ∼ 30-36 % g, and the PGV is ∼ 21-24 cm/s for a 5 km hypocentre depth. Both faults potentially produce destructive earthquakes (Mw > 6.0) in Yogyakarta City and its vicinity. Therefore, assessments of (paleo) earthquakes are needed of both the Opak Fault and the Merapi-Merbabu Fault to support the long-term earthquake hazard mitigation program.

SEISMIC PROPERTIES AND FRACTAL DIMENSION OF SUBDUCTION ZONE IN JAVA AND ITS VICINITY USING DATA FROM 1906 TO 2020

As the highest population density area in Indonesia which experienced tsunami-earthquakesin 1921 (Mw7.6), 1994 (Mw7.6), and 2006 (Mw7.7), the Java region has the threat of seismic activities, which could inflict great losses. Several seismic hazard studies have been carried out, but essential parameters have not been explicitly identified, and data on earthquake return periods remain limited. This study addresses such issues by identifying the seismic properties, including the seismic activity (a-value), frequency magnitude distribution related to the tectonic parameter (b-value), fractal dimension (D), and maximum magnitude (Mmax) of the subduction zone along the Java Island. The earthquake data used are those from 1906 to 2020. The research started with the processing of earthquake data, continued by determining the a-b values of Gutenberg-Richter relation using the maximum likelihood method.The fractal dimensionswere estimated based on the fracture distance and the maximum magnitudeswere calculated using some return period scenarios. Our results show that low seismic activity levels are relatively consistent with a low b-value pattern. The lowest b-values are in the south coast of West Java and the south coast of Central-East Java. Based on thefractal dimension analysis, theinterplate zones have a more complex fault geometry than intraplate ones. The maximum earthquake magnitude estimation of each subduction segment is presented and discussed comprehensively in this paper. These findings will redound to the benefit of earthquake and tsunamidisaster mitigation and earthquake modeling efforts for future seismic hazard studies.

De la neotectónica a la amenaza sísmica en América Latina y el Caribe

Today it is understood that the seismic risk, as well as any type of risk, is proportional to the disastrous combination of the seismic threat and the vulnerability of the exposed systems. Considering that the seismic threat is of natural origin, therefore not modifiable or controllable by man to any extent - unlike other threats that are anthropic or generated by man himself (eg nuclear explosions, seismicity induced by dams or reservoirs of water, etc.) if they are-, risk reduction is achieved both by increasing resilience (a system's own capacity to recover from an adverse event) and by reducing the exposure of potentially exposed systems. However, it should be noted that risk can be better characterized and quantified if the threat is better defined and known, even though it cannot be controlled. That is why the seismic threat needs to be the best bounded, measured and defined, to the extent of the available information, in order to reduce uncertainties to the maximum. It then requires that the seismic activity of the region under study be studied in detail, which also implies identifying and characterizing the generating sources of these earthquakes (seismogenic faults); that is, the geological faults responsible for such seismicity (seismotectonic association; Figure 1). It is customary in seismic hazard studies to study both aspects (source faults and seismicity) in a radius of at least 200 km; distance resulting from the attenuation of seismic energy as it propagates through the medium. So it is understood that the seismic energy released during most large earthquakes is expected to be attenuated to low hazard levels at that distance. The built environment located in sedimentary basins filled with soft or little consolidated sediments, such as the cases of Mexico City and Caracas, probably escape this practice, due to wave amplification effects as a site effect, which could be excited by large shallow or shallow earthquakes. subduction, with epicenters beyond that distance prescribed by practice. Consequently, it is necessary to retrace the seismic history –or earthquake chronology, which is the sum of the instrumental, historical and pre-historical earthquakes that make up the entire seismic activity (Audemard, 2019) - of the region surrounding the site. subject to a seismic hazard assessment (EAS; in English, Seismic hazard Assessment -SHA-), in the most complete way, as well as extensive in the time possible, in order to determine two fundamental parameters when calculating said estimate: the Maximum probable earthquake and the return period of large earthquakes with destructive capacity, for each of the identified faults, or their individual segments if they are defined. Given that these EAS can be addressed by two approaches, probabilistic and deterministic (or various combinations of both), the longest in time is the evaluated period, the statistical evaluations of both parameters indicated above - known under the term of seismogenic potential- , they will be more robust and reliable to estimate the seismic threat.

Shallow slow earthquakes to decipher future catastrophic earthquakes in the Guerrero seismic gap

The Guerrero seismic gap is presumed to be a major source of seismic and tsunami hazard along the Mexican subduction zone. Until recently, there were limited observations at the shallow portion of the plate interface offshore Guerrero, so we deployed instruments there to better characterize the extent of the seismogenic zone. Here we report the discovery of episodic shallow tremors and potential slow slip events in Guerrero offshore. Their distribution, together with that of repeating earthquakes, seismicity, residual gravity and bathymetry, suggest that a portion of the shallow plate interface in the gap undergoes stable slip. This mechanical condition may not only explain the long return period of large earthquakes inside the gap, but also reveals why the rupture from past M < 8 earthquakes on adjacent megathrust segments did not propagate into the gap to result in much larger events. However, dynamic rupture effects could drive one of these nearby earthquakes to break through the entire Guerrero seismic gap.

Model system dynamics potential impact of disasters due to the re-period of the October 25th, 2010 earthquake in the Mentawai Islands

Geographically, the Mentawai Islands Regency has a territorial boundary with the sea. The north side is the Siberut Strait, the south side is bordered by the Indian Ocean, the east side is bordered by the Mentawai Strait, and the west side is bordered by the Indian Ocean. The Mentawai Islands Regency area has a high level of seismicity which makes it prone to earthquakes and tsunamis because it has an earthquake return period. Population and economic growth in the Mentawai Islands Regency continue to increase, resulting in a higher level of threat due to earthquakes and tsunamis to people and buildings. By using earthquake return period modeling based on secondary data and population and building growth modeling using system dynamics, Pentahelix can implement disaster risk mitigation in the Mentawai Islands Regency to reduce the risk of casualties and material losses. Based on the prediction that the Mentawai earthquake return period on October 25, 2010, will occur for 24 years to 57 years or around 2034 to 2067, and the results of system dynamics modeling with Powersim Studio 10 software, the number of vulnerable people affected is 24,764 people up to 42,944 people and potential losses. housing sector between 144.73 billion to 250.98 billion.

ONE DIMENSIONAL SEISMIC RESPONSE ANALYSIS AT THE NON-COMMERCIAL NUCLEAR REACTOR SITE, SERPONG - INDONESIA

One dimensional seismic response analysis on the ground surface of the Non-Commercial Power Reactor (RDNK) site based on the mean uniform hazard spectrum (UHS) and disaggregation analysis has been conducted. The study’s objective was to perform an analysis on site-specific response spectra on the ground surface based on existing mean UHS and disaggregation data of the site that correspond to a 1,000 and 10,000 year return period of earthquakes in compliance with the national nuclear regulatory body requirements of Indonesia. Detailed site characterization was defined based on secondary data of a geotechnical drill-hole, seismic cross-hole, downhole data, and microtremor array data. The dynamic site characteristic analysis was presented along with strong motion selection and processing using two types of strong motion datasets. An investigation of strong motion selection, spectral matching, and scaling has been presented as an essential step in ground motion processing. One-dimensional equivalent linear analysis simulation was performed by computing the processed ground motions. A seismic design spectrum and ground surface response spectra from the two datasets of strong motion, both corresponding to a 10,000 and 1,000 year return period, are presented at the end of this study. This study has shown that in order to establish the appropriate seismic response design spectrum, site-specific data and seismic hazard analysis must be immensely considered.

Assessment on earthquake resistance spectral design load criteria for buildings and infrastructures in Indonesia

General assessment on earthquake resistance spectral design load criteria for buildings and infrastructures associated with the recent development of Indonesian seismic hazard maps is presented in this paper. The assessment is directed toward general identification of their associated risks for input to policy formulation of disaster risk reduction management plans or strategies. Indonesian seismic hazard maps haveevolved for the last three decades. This is originated from an early development map before 2002, where a seismic hazard map particularly for buildings (1983) was developed adopting the early process of probabilisticseismic hazard analysis (PSHA) for 200 years return period (RP). Further, a 2002 version seismic hazard maphas been developed in the form of peak ground acceleration (PGA) for 500 years RP. Spectral design criteriafor buildings and bridges have been later developed by updating PSHA involving new seismic source zones, ground-motion predictive equations, and various earthquake RP, accommodating seismic codes for buildings(2500 years RP), for bridges (1000 years RP) and dams involving various RP up to 10,000 years RP correspond to its design level. The spectral accelerations also have included PGA, short (0.2s) period, and 1-s period. The latest update hazard maps (2017) have been developed and adopted for seismic codes for buildings, bridges, dams, and other related infrastructures. The increase in spectral design load criteria is identified to assess the general risk of existing constructions, considering the results of several recent building damage surveys. Adoption of new seismic codes based on the most recent hazard maps along with its enforcement is expected to contribute to seismic disaster risk reduction in Indonesia.

Appraisal of Main Extreme Parameters of Earthquakes in Nigeria Using the Weibull Equations

This study investigated earthquake occurrences in Nigeria using the Weibull equations. The data employed in this study was the historical and instrumental data recorded from 1933 to 2018. The relationship between intensity scale and Richter magnitude scale given by Gutenberg and Richter&#x0D; was used to convert from intensity scale to Richter scale. The Weibull equations were used to compute probabilities and return periods of earthquakes. The findings of the study revealed that the return period for an earthquake of magnitude 6.5 on Richter’s scale is 86 years; an earthquake of magnitude 4.7 is 34.4 years; an earthquake of magnitude 4.2 is 17.2 years and earthquake of magnitudes 2-3.7 is between 5.56-14.3years. This implies that Nigeria may not likely experience any earthquake of magnitude 6.5 till the year 2025 since earthquake of magnitude 6.5 last occurred in 1939 but the probability of occurrence is 1.16% or 0.0116. Earthquakes of highest magnitudes 6.5, 4.7 and 4.2 on Richter’s scale for a 100 year period which indicate the most hazardous in the location with probabilities exceedance of 1.16%, 2.91% and 4.65% were evaluated. It was observed that as the time increases the probability of occurrence of these earthquakes increases with it and vice versa with magnitude 4.2 having (99.1%), magnitude 4.7 having (94.8%) and magnitude 6.5 having (80.07%). But earthquake forecast or prediction is still a complicated issue due to saturation of earthquake magnitudes and variation in seismic data collection by different seismic stations and networks. The implication of this study is that the findings will help Nigeria government to protect its people, infrastructures and the constructions that are going to take place especially earthquake – prone areas like southwestern Nigeria.

Impacts of simulated M9 Cascadia Subduction Zone earthquakes considering amplifications due to the Georgia sedimentary basin on reinforced concrete shear wall buildings

AbstractSouthwest British Columbia has the potential to experience large‐magnitude earthquakes generated by the Cascadia Subduction Zone (CSZ). Buildings in Metro Vancouver are particularly vulnerable to these earthquakes because the region lies above the Georgia sedimentary basin, which can amplify the intensity of ground motions, particularly at medium‐to‐long periods. Earthquake design provisions in Canada neglect basin amplification and the consequences of accounting for these effects are uncertain. By leveraging a suite of physics‐based simulations of M9 CSZ earthquakes, we develop site‐specific and period‐dependent spectral acceleration basin amplification factors throughout Metro Vancouver. The M9 simulations, which explicitly account for basin amplification for periods greater than 1s, are benchmarked against the 2016 BC Hydro ground motion model (GMM), which neglects such effects. Outside the basin, empirical and simulated seismic hazard estimates are consistent. However, for sites within the basin and periods in the 1‐5 s range, GMMs significantly underestimate the hazard. The proposed basin amplification factors vary as a function of basin depth, reaching a geometric mean value as high as 4.5 at a 2‐s period, with respect to a reference site located just outside the basin. We evaluate the impact of the M9 simulations on tall reinforced concrete shear wall buildings, which are predominant in the region, by developing a suite of idealized structural systems that capture the strength and ductility intended by historical seismic design provisions in Canada. Ductility demands and collapse risk conditioned on the occurrence of the M9 simulations were found to exceed those associated with ground motion shaking intensities corresponding to the 975 and 2475‐year return periods, far exceeding the ∼500‐year return period of M9 CSZ earthquakes.

Prijedlog spektara odziva u drugoj generaciji Eurokoda EN1998-1-1 za seizmička područja i usporedba s postojećom normom EN 1998-1: 2004

Fundamental changes of the existing standard EN 1998-1, with incorporation of latest research results, are proposed in the second generation of Eurocode EN 1998-1-1. A spectrum of earthquake loads, defined by several points established in a probabilistic manner, is presented and commented on. In addition, the new EN 1998-1-1: a) introduces 12 return periods for earthquakes (instead of the previous two periods), b) cancels previous elastic spectra Type 1 and Type 2, c) introduces a new moment magnitude Mw instead of the surface magnitude Ms, d) introduces four limit states instead of the previous two NCR and DLR, etc.