Future Earthquakes Research Articles

Stress dissipation and seismic potential in the central seismic gap of the north-west Himalaya

• One-third of the earthquakes in CSG show stress drop <1 bar. • High stress drop events are absent in the upper 10 km of the crust. • Source parameter values are lower in Kumaon than CSG. • Kangra and Kumaon segments can be tipped to host a future great earthquake. The central seismic gap (CSG) of the Himalaya continues to pose the ever more intriguing question of whether it has the potential to host a devastating earthquake. To address the issue, we examine the distribution and dissipation of post-seismic stress in the northwest segment of the CSG. This study computes the source parameters of 47 local earthquake events (3.5 ≤ M L ≤ 5.5) in the Garhwal-Kumaon Himalaya during the period 2016–2018 using P-wave spectral analysis. In addition, we compile the stress drop results for 326 earthquake events from numerous studies carried out across the seismic gap, to estimate the source parameter variation. The estimated seismic moments (10 12 ≤ M o ≤ 10 16 N-m), source radii (0.3 ≤ r ≤ 1.3 km) and stress drops (0.1 ≤ σ ≤ 40.6 bar) for Kumaon are observed to be significantly lower than the overall values for the CSG (10 10 ≤ Mo ≤ 10 20 N-m; 0.1 ≤ r ≤ 13.2 km; 0.01 ≤ σ ≤ 77 bar), showing incomplete dissipation of the accumulated stress. About one-third of the earthquakes in the CSG show very low stress drop (σ < 1 bar). The high stress drop events are predominant along the Main Himalayan Thrust at mid-crustal depths, with the upper ∼ 10 km of the brittle crust rarely hosting any big event. Based on the analysis, the scaling relation M o f c 3.677 = 6E + 15 N-m/s 3 has been proposed for the Kumaon region. Other scaling relations have been developed between important source parameters (M L , M w , M o , and σ) that may serve as valuable inputs for assessing the earthquake hazard in the region. The estimated b-value for the Kumaon Himalaya estimated from the local earthquake catalog is 0.64 ± 0.08, which is low compared to the Garhwal and rest of the NW Himalaya. The overall b-value of the CSG region computed from the ISC catalog is 0.62 ± 0.06. From the stress drop and b-value variation in the CSG, the Kangra and the Kumaon segments are identified to be potentially hazardous zones for a future great earthquake.

Back-projection results for the M w 7.5, 28 September 2018 Palu earthquake-tsunami

A back-projection technique allows seismologists to analyse rupture properties once seismic signals from a dense array of seismic networks are available. The observed waveforms are then traced back in space and time to the source region of an earthquake under investigation. In this study, the method utilised the back-projection image of the recorded high-frequency P-seismic waveforms filtered at 0.25-1.0 Hz by Multiple Signal Classification (MUSIC) processing to estimate the extent and the spread of earthquake rupture propagation of the M w 7.5 Palu event on 28 September 2018, generating a severe tsunami. This study aims to estimate rupture duration, its extent (the distance over which rupture propagates) and the corresponding speed, and rupture directivity (where most of the seismic energy propagates). The results revealed that the front of rupture propagates slightly offset southward at about 2.9 km/s over a distance of ~140 km away from the epicentre for about 49 s before slowing down at much smaller amplitudes after reaching the south end of Palu Bay. This finding is consistent with an NNW-SSE orientation of the active Palu-Koro Fault lying along the bay, suggesting that the strong ground motion is associated with the fault activities. This study has therefore substantial implications for enhanced earthquake and tsunami early warnings, helping the government and local authority build community resilience by warning people at risk from future possible earthquake and tsunami hazards.

Development of Fragility Curves for the Underground PVC Water Distribution Pipes in Quezon City and Damage Estimation under a Magnitude 7.2 Scenario Earthquake

Quezon City is traversed by the West Valley Fault System (WVFS) that has the capability of generating a magnitude 7.2 earthquake known as “The Big One”. It has an extensive water distribution network that is very susceptible to damages that will be caused by the ground shaking component of the M 7.2 earthquake. This study focuses on determining the behavior and estimating the damage of underground polyvinyl chloride (PVC) water pipes due to the M 7.2 earthquake by using appropriate empirical repair rates (RR) and developing fragility curves. The appropriate empirical RR equation was determined by comparing the results of selected PVC RR equations and the simulation using line-element modeling. The PGV ranges from 23.10 cm/s to 64.49 cm/s as determined using the Boore and Atkinson (2008) ground motion prediction equation. Using the results from the empirical and simulations methods, the equation by the American Lifelines Alliance (2001) was determined to be the appropriate empirical RR equation for the study area. The expected average repair rate of PVC is 0.05 repairs/km length of pipe or an estimated 84 total PVC pipe repairs in the city. Three fragility curves were generated showing the relationship of PGV and RR which is an important tool in estimating the underground pipe damages with respect to the M 7.2 earthquake and other future earthquakes of similar properties.

Seismic Activities and Hazards of the Seismic Gaps in the Haiyuan Fault in Northeastern Tibet: Insights From Numerical Modeling Earthquake Interaction

AbstractThe 2022 Mw 6.6 Menyuan earthquake occurred in the Qilian‐Haiyuan fault system in northeastern Tibet. To investigate the mechanism behind the 2022 Menyuan earthquake and the seismic hazards (SHs) of the Tianzhu seismic gap, the spatiotemporal stress variations on the Qilian‐Haiyuan fault zone were assessed before and after 2022 by modeling the stress changes caused by 12 historical large earthquakes during the last century. The results showed that the 2022 Menyuan earthquake was delayed due to a stress shadow caused by the 1927 Mw 8.3 Gulang earthquake. The stress shadow also covers the middle section of the Tianzhu seismic gap and inhibits its seismic activities to some extent. By preventing the rupture of the Tianzhu seismic gap in a single event, this stress shadow may reduce the risk of a future earthquake with a magnitude of more than Mw 7.7 in the Tianzhu seismic gap (length = approximately 260 km). The western portion of the Tianzhu Seismic Gap (length = approximately 18 km) was stress‐loaded with the peak ΔCFS value of approximately 375.15 kPa due to the 2016 Mw 5.9 and 2022 Mw 6.6 Menyuan earthquakes, indicating its increased SHs. The eastern portion of the Tianzhu seismic gap (length = approximately 149 km) was stress‐loaded with the peak ΔCFS value of approximately 1,035 kPa due to the 1927 Mw 8.3 Gulang and 1920 Mw 8.5 Haiyuan earthquakes, indicating its increased SHs. Therefore, more efforts should be made to prepare for the future hazards prevention in the eastern portion of the Tianzhu seismic gap.

Estimation of the finite fault source model for the 2018 Mw7.1 Acari, Peru earthquake using a hybrid simulation prediction approach

The near-field motion of large earthquakes is generally simulated using finite fault source models (FFSMs). Most of these models use post-earthquake observation data as the constraints for the inversion model, and therefore, it is difficult to generate FFSMs until after the earthquake has occurred. We use parameters from previous earthquakes to generate FFSMs in a hybrid simulation prediction approach that combines the asperity model and the k−2 model. New scaling laws for global and local parameters are used to estimate the asperity model parameters and the coordinates of the fracture initiation point. Using the k−2 model, 30 sets of FFSMs are established using truncated normal distributions and several regional geological structural parameters. After applying the residual evaluation criteria to the various response spectra, we select the average source model. We then apply our methodology to the 2018 Acari earthquake in Peru. Both our average model and the USGS inversion model have two asperities, but their positions are different. The response spectra of the four representative points of our model are similar to those of the USGS model, and the peak difference is between −13.4% and 18.4%. The USGS model is a post-earthquake model, which requires many parameters and post-earthquake observation data. Our FFSM requires few parameters and represents the most representative source model for future earthquakes in this area with similar magnitudes, and it is intended to be supplementary to the inversion model. Therefore, our hybrid approach may be used for the early prediction or rapid estimation of the resulting ground motions.

A Framework of Systematic Land Use Vulnerability Modeling Based on Seismic Microzonation: A Case Study of Miri District of Sarawak, Malaysia

The objective of this research is to develop the framework for sustainable land-use planning on the basis of seismic microzonation to reduce the devastating effects of future earthquakes by utilizing the software geographical information system (ArcGIS). Miri district of Sarawak in Malaysia has been chosen as the study area because of having the highest peak ground acceleration which is 0.09g in terms of the 10% probability of exceedance in 50 years. In addition, the frequency of an earthquake with a magnitude up to 5.3 is approximately every 5-7 years. Therefore, it is vital to introduce land use planning in order to diminish the adverse effects of earthquakes in the future. For this purpose, Google Earth Pro was used for the collection of satellite image data for land use planning purposes. From the results, it was found that the seismic hazard in the Miri district varies from low to high corresponding to 2475 years of return period with low to moderate as predominant over the Miri district. Only a few areas are under high hazard. Also, the land use planning map was compared with the current land use map acquired from satellite imagery and it was found that all built-up is in the low hazard area. It is envisaged that the findings from this research will contribute immensely to the literature that will serve as background information and a guide for analysts, disaster management, engineering designers and seismologists in Malaysia and the world as a whole.

The earthquake environmental effects (EEEs) of the 6th February 2018, Hualien earthquake (Mw=6.4): A contribution to the seismic hazard estimation in the epicentral area

The macroseismic intensity of the February 6, 2018, Mw 6.4, Hualien earthquake, which caused extensive damage around the Hualien area of eastern Taiwan is reassessed using the Environmental Seismic Intensity (ESI-07) scale. We compiled data on earthquake environmental effects (EEEs) caused by the 2018 Hualien earthquake, which includes surface ruptures, ground cracks, liquefaction, and occasional landslides, and estimated the epicentral intensity (I0) as well as site-specific intensities. We found that the ESI-07 epicentral intensity of the Hualien quake in 2018 is IX. We note that the epicentral area of the 2018 Hualien earthquake was the mesoseismal area of the October 22, 1951, (Mw 6.6) Hualien earthquake, as reported in primary contemporary sources and historical earthquake catalogs. The 1951 Hualien earthquakes also caused prominent surface ruptures, liquefaction, and ground cracks. Consequently, we reassess the macroseismic intensities of this historical seismic event and compare it to the Hualien earthquake in 2018. The comparison suggests similar epicentral intensities for the two earthquakes (IX and X ESI-07). Moreover, we conducted a systematic comparison between intensity obtained using different scales which revealed the differences of two to three degrees between the ESI-07 and traditional intensity scales. This result reconfirms the significance of documentation and recording of earthquake environmental effects to make intensity assessments for modern seismic events consistent with the historical earthquake records. Moreover, a re-evaluation of historical earthquake intensity in eastern Taiwan could be performed in order to update the seismic hazard map. Application of the ESI-07 intensity scale of recent and historical earthquakes will be helpful in post-earthquake recovery efforts for a future earthquake. The prepared ShakeMaps from the ESI-07 values suggests completely different shapes to the previously generated ShakeMaps considering the peak ground acceleration or peak ground velocity. It suggests that the ShakeMaps prepared from the earthquake environmental effects can be complemented with the instrumental based intensity map to have a better seismic hazard prediction and future land use planning for the region.

Ensuring Earthquake-Proof Development in a Swiftly Developing Region through Neural Network Modeling of Earthquakes Using Nonlinear Spatial Variables

Northern Pakistan, the center of major construction projects due to the commencement of the China Pakistan Economic Corridor, is among the most earthquake-prone regions globally owing to its tectonic settings. The area has experienced several devastating earthquakes in the past, and these earthquakes pose a severe threat to infrastructure and life. Several researchers have previously utilized advanced tools such as Machine Learning (ML) and Deep Learning (DL) algorithms for earthquake predictions. This technological advancement helps with construction innovation, for instance, by designing earthquake-proof buildings. However, previous studies have focused mainly on temporal rather than spatial variables. The present study examines the impact of spatial variables to assess the performance of the different ML and DL algorithms for predicting the magnitude of short-term future earthquakes in North Pakistan. Two ML methods, namely Modular Neural Network (MNN) and Shallow Neural Network (SNN), and two DL methods, namely Recurrent Neural Network (RNN) and Deep Neural Network (DNN) algorithms, were used to meet the research objectives. The performance of the techniques was assessed using statistical measures, including accuracy, information gain analysis, sensitivity, specificity, and positive and negative predictive values. These metrics were used to evaluate the impact of including a new variable, Fault Density (FD), and the standard seismic variables in the predictions. The performance of the proposed models was examined for different patterns of variables and different classes of earthquakes. The accuracy of the models for the training data ranged from 73% to 89%, and the accuracy for the testing data ranged from 64% to 85%. The analysis outcomes demonstrated an improved performance when using an additional variable of FD for the earthquakes of low and high magnitudes, whereas the performance was less for moderate-magnitude earthquakes. DNN, and SNN models, performed relatively better than other models. The results provide valuable insights about the influence of the spatial variable. The outcome of the present study adds to the existing pool of knowledge about earthquake prediction, fostering a safer and more secure regional development plan involving innovative construction.

Coseismic Faulting Complexity of the 2019 Mw 5.7 Silivri Earthquake in the Central Marmara Seismic Gap, Offshore Istanbul

Abstract The submarine Main Marmara fault is overdue for an M &amp;gt; 7 earthquake in direct vicinity to the Istanbul megacity and the only segment of the right-lateral North Anatolian fault zone that has not been activated since 1766. On 26 September 2019, an Mw 5.7 earthquake occurred offshore Silivri (west of Istanbul), stimulating the discussions on a future major earthquake. The predominant faulting style for this pending earthquake remains enigmatic. Here, we study the coseismic rupture evolution of the 2019 Silivri earthquake and decipher the multitype-faulting aspects by a nonstandard approach. The event was dominated by a large compensated linear vector dipole component, of about −50%, that we interpret as a consecutive strike-slip and thrust double-couple episode, closely collocated in space and time. Because of local variations of the fault geometry at the eastern boundary of the central basin, crustal shortening and related thrust faulting are expected. A striking observation is the almost synchronous occurrence of both faulting types during a single earthquake. The earthquake complexity here is reported for the first time in the Sea of Marmara region and has to be considered in future rupture scenarios of an expected M &amp;gt; 7 event, with subsequent consequences for tsunami hazard and risk.

System dynamics modeling of the earthquake-induced interruption of a business

ABSTRACT This study proposes a system dynamics simulation model that characterizes the dynamics post-earthquake performance of a business considering its dependency on lifelines (i.e., utilities and road networks) and the state of the market. The model characterizes the relationships between the business’s profitability and the resources it needs to operate (e.g., staff, raw materials, and equipment). It also considers the supply and demand dynamics that govern the prices of goods or services the business produces. It can be used to holistically investigate a business’s post-earthquake performance and recovery. It helps administrators acquire an insight into how to reduce the vulnerability of their businesses against probable future earthquakes. The model application is showcased by applying it to simulate the post-earthquake performance and recovery of a manufacturing business. The results indicate that, unlike retrofits, post-earthquake measures like increasing prices or changing shipping policies do not adequately mitigate earthquake-induced business losses.

Integrated seismic risk assessment in Nepal

Abstract. Seismic risk analysis is necessary to mitigate the potential losses resulting from future earthquakes and supplement scientific risk management. In order to assist systematic evaluation and management of risk, it is indispensable to interpret risk in terms of social and economic consequences due to hazardous events like earthquakes. There is an interrelationship between hazards, physical risk, and the social characteristics of populations. Therefore, based on the existing studies focusing on each of these aspects, this paper presents the integrated seismic risk assessment along the subdivisional administrative units of Nepal using 2011 census data. The administrative unit “provinces” are subdivided into districts and each district into municipalities and village development committees (VDCs). The districts, municipalities, and VDCs were considered as our study units. In this paper, the physical or seismic risk was evaluated from the exposure model, hazard curves, and the vulnerability model of the country, whereas the social vulnerability was assessed using social vulnerability index (SoVI) methods. To formulate the physical risk, the assets used were five types of buildings under the exposure model. This model was combined with the physical vulnerability functions of the building and the hazard curves of the country. The result of the physical risk has been presented as annual average loss (AAL). Similarly, among 92 social vulnerability variables, 54 variables were reduced to 7 weighted parameters using principal component analysis (PCA). The scores of a total of 45 parameters were used to evaluate the SoVI index, which was further combined with the physical risk to evaluate integrated risk. The results showed that populated cities like Kathmandu, Hetauda, and Janakpur have a highly integrated risk index. Similarly, the Terai region bordering its neighbor India and some parts of the central hilly region are highly vulnerable, while most parts of the mountainous region in the central and eastern regions are the least vulnerable. The results from the present study can be utilized as a part of a comprehensive risk management framework at the district level to recuperate and recover from earthquakes.

Calibration of a Bayesian spatio-temporal ETAS model to the June 2000 South Iceland seismic sequence

SUMMARY The reliable forecasting of seismic sequences following a main shock has practical implications because effective post-event response is crucial in earthquake-stricken regions, aftershocks can progressively cause increased damage and compound economic losses. In the South Iceland Seismic Zone (SISZ), one of two large transform zones in Iceland where earthquake hazard is the highest, an intense seismic sequence took place during 17–24 June 2000, starting with a ${M}_{\rm{w}}$ 6.4 main shock on 17 June 2000, followed by another ${M}_{\rm{w}}$ 6.5 main shock four days later and on a different fault. Both earthquakes caused considerable damage and incurred heavy economic losses. They were immediately followed by intense aftershock activity on the causative faults and triggered earthquakes as far as 80 km away along the transform zone. To investigate the feasibility of forecasting the progression of such complex sequences, we calibrated a spatio-temporal epidemic-type aftershock sequence (ETAS) clustering model to the June 2000 seismic sequence in the framework of Bayesian statistics. Short-term seismicity forecasts were carried out for various forecasting intervals and compared with the observations, the first generated a few hours after the first main shock and followed by daily forecasts. The reliability of the early forecasts was seen to depend on the initial model parameters. By using an adaptive parameter inference approach where the posteriors from each preceding forecasting interval served as informative priors for the next, the fast convergence of the parametric values was ensured. As a result, the 16–84 percentile range of the forecasted number of events captured the actual number of observed events in all daily forecasts, and the model exhibited a strong spatial forecasting ability, even only a few hours after the main shock, and over all subsequent daily forecasts. We present the spatio-temporal ETAS parameters for the June 2000 sequence as ideal candidates of prior estimates for future operational earthquake forecasting of other Icelandic aftershock sequences. Past seismic sequences need to be analysed retrospectively to confirm the stability of the parameters of this study, effectively enable the application of the Bayesian ETAS model as an operational earthquake forecasting system for aftershocks in Iceland.

Pseudo-prospective testing of 5-year earthquake forecasts for California using inlabru

Abstract. Probabilistic earthquake forecasts estimate the likelihood of future earthquakes within a specified time-space-magnitude window and are important because they inform planning of hazard mitigation activities on different time scales. The spatial component of such forecasts, expressed as seismicity models, generally relies upon some combination of past event locations and underlying factors which might affect spatial intensity, such as strain rate, fault location and slip rate or past seismicity. For the first time, we extend previously reported spatial seismicity models, generated using the open source inlabru package, to time-independent earthquake forecasts using California as a case study. The inlabru approach allows the rapid evaluation of point process models which integrate different spatial datasets. We explore how well various candidate forecasts perform compared to observed activity over three contiguous 5-year time periods using the same training window for the input seismicity data. In each case we compare models constructed from both full and declustered earthquake catalogues. In doing this, we compare the use of synthetic catalogue forecasts to the more widely used grid-based approach of previous forecast testing experiments. The simulated catalogue approach uses the full model posteriors to create Bayesian earthquake forecasts, not just the mean. We show that simulated catalogue based forecasts perform better than the grid-based equivalents due to (a) their ability to capture more uncertainty in the model components and (b) the associated relaxation of the Poisson assumption in testing. We demonstrate that the inlabru models perform well overall over various time periods: The full catalogue models perform favourably in the first testing period (2006–2011) while the declustered catalogue models perform better in the 2011–2016 testing period, with both sets of models performing less well in the most recent (2016–2021) testing period. Together, these findings demonstrate a significant improvement in earthquake forecasting is possible although this has yet to be tested and proven in true prospective mode.

Evidence of Active Quaternary Deformation on the Great Valley Fault System near Winters, Northern California

Abstract The Great Valley fault system defines the tectonic boundary between the Coast Ranges and the Central Valley in California, is active throughout the Quaternary, and has been the source of several significant (M &amp;gt; 6) historic earthquakes, including the 1983 M 6.5 Coalinga earthquake and the 1892 Vacaville–Winters earthquake sequence. However, the locations and geometries of individual faults in the Great Valley fault system are poorly constrained, and fault slip rates and paleoearthquake chronology are largely unknown. Here, we report geomorphic and subsurface geophysical evidence of surface-deforming displacement on a strand of the Great Valley fault system west of Winters, California. Detailed geomorphic mapping and a high-resolution seismic reflection and tomography survey along an ∼800 m profile across the Bigelow Hills document a fault, which we call the West Winters strand of the Great Valley fault system, with apparent east side-up displacement of surficial geologic units. These data together suggest that the West Winters strand is active in the latest Quaternary. Together with local reports from the time, this raises the possibility that the West Winters strand may have ruptured and deformed the surface during the 1892 M 6 Vacaville–Winters earthquake sequence. Future earthquakes with vertical displacement on this and Great Valley fault system structures could have significant hazard implications, given the region’s low relief and the presence of major water conveyance infrastructure.

Prospects for developing methods for short-term forecasting of strong earthquakes based on satellite monitoring of cloudiness anomalies

Forecasting earthquakes of various intensities will continue to be an urgent task that has yet to bene resolved. The use of various forecasting methods makes it possible to conduct analysis and warnings more objectively and reliably. Methods of short-term prediction of strong earthquakes based on satellite monitoring of cloudiness anomalies can be used with some success. Based on the research results, it was established that before strong earthquakes, linear cloudiness anomalies are observed over the Earth's deep fault zones, which can be used for short-term earthquake forecasting. The most effective method of studying cloudiness anomalies is the use of satellite methods. As a result of the analysis of linear cloudiness anomalies, a conclusion was made about the possibility of a regional short-term forecast of strong and catastrophic earthquakes with an assessment of the possible magnitude and approximate position of the future earthquake. The reliability of the forecast depends on the tectonic structure of the region and atmospheric conditions. It is important to be able to forecast the magnitude of the future earthquake based on the length of the cloudiness anomaly. It was established that the length of the cloudiness anomaly before a catastrophic earthquake allows one to predict the magnitude, which is very important for forecasting the level of seismic danger in the coming days.

Cyclic Behavior of Retrofitted Low- and High-Strength Concrete Scaled Bridge Piers under Quasistatic Loading

Bridges are vulnerable to devastation in the earthquake, resulting in the closure of the whole transport system of the particular region. Generally, pre-Kashmir earthquake bridges in Pakistan were not designed according to present seismic zoning requirements. Therefore, it is critical to evaluate their seismic performance and accordingly enhance their strength, stiffness, and thus reliability. Seismic retrofitting of existing bridges with CFRPs (carbon fiber-reinforced polymers) may be planned for typical bridge types of Pakistan. High-strength concrete (HSC) is now widely used in bridge construction, and the seismic behavior of typical bridge piers being a key component needs to be assessed. This investigation aims to evaluate the seismic performance of HSC piers before and after retrofitting in association with the earlier research in Pakistan on low-strength concrete prototypes. An experimental program was executed wherein scaled-down (4 : 1) HSC (6192 psi) RC bridge pier prototypes with axial load at the top were subjected to quasistatic cyclic loadings (QSCLs) under controlled drifts. The damaged pier prototypes were retrofitted with CFRP sheets beside another set of undamaged retrofitted models. The samples were tested under QSCL against several drift levels ranging from 0 to 5%. Hysteresis loops were drawn for each sample. The tests were studied for the assessment of the structural behavior of the prototypes. The results for the control models, damaged retrofitted models, and undamaged retrofitted models of low-strength concrete (LSC, 1800 psi and 2400 psi) obtained from doctoral research by Ali and Iqbal were compared with corresponding models of high-strength concrete (6192 psi). The outcomes clearly show a noteworthy increase in lateral load carrying capacity, ductility, strength, and energy absorption on an increase in concrete strength and retrofitting of the prototypes. The numerical modeling of these piers was in consistence with the experimental results. When retrofitted with CFRP, the existing bridge piers will enable the bridge stock to withstand high-intensity future earthquakes and lessen their seismic vulnerability against prospective damages.

Development of LSN-based pipe repair rate models utilising data from the 2011 Christchurch earthquakes

The Canterbury Earthquake Sequence (CES) adversely impacted built, economic and social environments. This included widespread physical damage to the water supply pipe network in Christchurch, resulting in long service disruptions. The transient and permanent ground deformations generated by the earthquakes in the CES caused a range of pipe damage, particularly in the MW 6.2 22 February 2011 and the relatively less damaging MW 6.0 13 June 2011 event. Damage to the pipes in both events was largely attributed to liquefaction and lateral spreading effects. Pipes made of ductile material (e.g. PVC, HDPE) sustained lesser damage (and therefore lower repair rates) compared to the pipes made of non-ductile material (e.g. AC, CI). In all cases, the repair rates (number of repairs per kilometre) typically increased with increasing liquefaction severity. Utilising the pipe repair dataset and Liquefaction Severity Number (LSN) maps generated from extensive geotechnical investigation following the CES events, new repair rate prediction models for water pipes subjected to liquefaction effects have been derived and are presented in this paper. Repair data from both earthquakes has been analysed independently and in combination, providing two sets of repair rate functions and different levels of uncertainty. Repair rate functions were first derived from pipes grouped by combination of diameter (i.e. ϕ &lt; 75 mm or ϕ ≥ 75 mm) and material type (i.e. ductile or non-ductile). The models were then refined by adding correction factors for those material types and diameters with sufficient sample length. Correction factors were derived for AC, CI, PVC pipes of diameter ≥75 mm and for MDPE and HDPE80 pipes of diameter &lt;75 mm. Galvanised Iron (GI) pipes performed poorly during the earthquakes, resulting in very high repair rates compared to the other non-ductile pipes of diameter &lt;75 mm damaged in the network; this warranted a separate repair rate model to be developed for this pipe type. The proposed models can be used in risk assessment of water pipe networks; i.e. to estimate the number of pipe repairs from potential liquefaction damage from future earthquakes.

Deterministic and Probabilistic Seismic Hazard Analysis of Tindharia, Darjeeling Sikkim Himalaya, India

Abstract The simulation of appropriate ground motion is the main objective in earthquake-resistant designing to mitigate the impact of landslides and structural damages. The seismic hazard studies serve as the basis for quantifying the hazard associated within the particular area over a given time period. In this study, the detailed site specific hazard analysis of Tindharia site as well as Darjeeling Sikkim Himalaya (DSH) region has been carried out to assure the safety of human and infrastructure against seismic risk. The study area is mountainous region on north western side of India, falls in seismic zone IV and V, and is one of the most seismically active regions with vulnerable earthquakes along with fatal landslides. The future large earthquakes are likely to occur in the region due to constant movement of Indian plate towards Eurasian plate. Therefore, the heightened seismic risk increases the demand for seismic studies near the Himalayan belt. Thus, the assessment of associated seismic hazard in the study area has been carried out by deterministic and probabilistic seismic hazard approaches. From the results, the seismo-tectonic map of a 300km radial distance of the study area is developed. The deterministic hazard distribution in terms of peak ground acceleration (PGA) and the PGA and peak spectral acceleration (PSA) hazard maps for 2% and 10% probability of exceedance in 50 years at different time periods have been generated. The updated hazard maps developed in this study play pivotal roles in mitigation measures with better pre-disaster prevention by earthquake resistant design and in preparedness and post disaster rescue in the study area.

PARAMETRIC STUDY ON TORSIONAL EFFECTS OF IRREGULAR BUILDING WITH STIFFNESS AND MASS IRREGULARITY UNDER SEISMIC ZONE

Due to the expanding population all throughout the world, there is an enormous need for the construction of high-rise structures. One of the most crucial ways to prevent damage from future earthquakes is the construction of engineering structures that are earthquake- resistant. Earthquake forces are irregular forces that may or may not cause structural damage. Failure starts in the weakest area during an earthquake. This weakness might be brought on by the structure's discontinuity in mass, stiffness, and shape. According to (IS: 18933, 2002), a story inside a building is considered to have mass irregularity only if its mass is greater than 200% of the story next to it. Average lateral stiffness or less than 70% of the stiffness in the level above. This paper presents the analysis conducted on the G+10 RC frame structure from zones II to V with mass and stiffness irregularities (response spectrum). The results show that the mass at the top floor was critical compared to other floors, whereas the stiffness at the ground floor was critical compared to other floors. Key Words: Earthquake, Response Spectrum, Mass and Stiffness Irregularity.

Strong ground motion data of the 2015 Gorkha Nepal earthquake sequence in the Kathmandu Valley

Strong-motion records of earthquakes are used not only to evaluate the source rupture process, seismic wave propagation and strong ground motion characteristics, but also to provide valuable data for earthquake disaster mitigation. The Kathmandu Valley, Nepal, which is characterised by having soft sediments that have been deposited in an earthquake-prone zone, has experienced numerous earthquakes. We have operated four strong-motion stations in the Kathmandu Valley since 2011. These stations recorded the 2015 magnitude 7.8 Gorkha Nepal earthquake that occurred in the Himalayan continental collision zone. For several months after the mainshock, we deployed four additional temporary stations. Here, we describe the seismic data for 18 earthquakes over magnitude 5.0 collected by this array, including the 2015 magnitude 7.3 Dolakha earthquake of maximum aftershock and three large aftershocks of magnitude 6-class. These data are essential for validating the sedimentary structure of the basin and for evaluating the hazard and risk of future earthquakes in the Kathmandu Valley.