Modified Mercalli Intensity Scale Research Articles

A future scenario earthquake and ground motion hazards for Kathmandu, Nepal

Since Nepal is an earthquake-prone country due to the collision of the Indian and Eurasian plates, it is crucial for its capital of Kathmandu to evaluate ground motion hazards from a future large earthquake. For this purpose, we constructed a realistic scenario earthquake with realistic rupture parameters in a likely location. To obtain the location, a new distribution of the rupture zones of large historical earthquakes along the Main Himalayan Thrust (MHT) was obtained by integrating the distribution from a previous study and the results of trench surveys. Global Navigation Satellite System observations indicated that the plate boundary is strongly coupled from the southern boundary of the MHT to a depth of approximately 10 km and there is almost no lateral change in the coupling. This implies that all regions along the MHT have similar rates of strain increase. Therefore, it is most probable that the rupture zone of the oldest previous event will rupture as a scenario earthquake. In the new distribution, the 1255 earthquake is the oldest. However, large earthquakes occurred in 1934 and 2015 within its rupture zone. Thus, we adopted the area obtained by removing the 1934 and 2015 rupture zones from the western part of the 1255 rupture zone. The relationship between the rupture area size and seismic moment of the 2015 earthquake lies between the scaling formulas for crustal earthquakes and plate-boundary earthquakes, but is closer to the former. Therefore, using this and the scheme for characterized source models, we determined realistic rupture parameters. We then simulated broadband ground motions in Kathmandu using these rupture parameters, our 3-D velocity structure models, and a hybrid method combining the finite-difference method and the stochastic Green’s function method. We obtained the peak ground accelerations (PGAs) of simulated ground motions, and calculated the seismic intensities in the Modified Mercalli intensity scale from the PGAs as indexes of hazards for Kathmandu. Intensities IX coincide with the center of the Kathmandu Valley, and intensities VIII and VII are found in the area surrounded by the sedimentary boundary and the southernmost part of the valley.Graphical abstract

Reappraisal of the 2012 magnitude (MW) 6.7 Negros Oriental (Philippines) earthquake intensity and ShakeMap generation by using ESI-2007 environmental effects

The macroseismic intensity of the February 6, 2012, Negros Oriental earthquake (MW 6.7), which affected the islands of Negros and Cebu, central Philippines, has been reassessed in this study using the Environmental Seismic Intensity Scale (ESI-2007). This earthquake caused a ∼75-km-long surface rupture along a previously unmapped fault and resulted in extensive landslides, localized liquefaction, lateral spreading, a tsunami, and widespread damage to infrastructure near the epicentral area. Considering the widespread earthquake environmental effects (EEEs), ESI-2007 intensities were evaluated for 324 locations covering an area of approximately 1000 km2 within the Negros and Cebu Islands. A systematic comparison was conducted between the ESI-2007 scale and the traditional intensity scales (PHIVOLCS earthquake intensity scale (PEIS) and Modified Mercalli Intensity scale (MM) along with the generation of an ESI-2007 shake map, which is solely based on site-specific ESI-2007 intensity values. According to the ESI-2007 scale, the epicentral intensity I0=X is assessed. This is two degrees higher than the intensity of the PEIS, and three degrees higher than the modified MM intensity provided by the United States Geological Survey (USGS). The intensity difference may also be due to the lack of suitable observations of building damage data in this sparsely populated region of the Philippines. Comparison of the ShakeMap that was constructed using the ESI-2007 intensities with the PHIVOLCS and USGS ShakeMap suggests that the instrumental or structural damage-based intensity maps underestimate the seismic intensity for the 2012 Negros Oriental earthquake. The ESI-2007 ShakeMap presented in this work is pertinent for the assessment of future seismic risk associated with other earthquake generators in the vicinity of the islands of Negros and Cebu. It can be integrated with the PEIS or MM intensity scale to improve disaster management and planning, post-earthquake recovery efforts, and damage estimation.

Human-induced seismicity and the public acceptance of hydraulic fracturing: A vignette experiment

Despite years of debate, hydraulic fracturing (HF) remains controversial. While the balance of perceived economic benefits and environmental costs of “fracking” has generated much debate, the question of whether citizens could accept the risk of induced earthquakes from HF remains largely unanswered. This paper uses data from a survey-based vignette experiment with (n=1,300) individuals in Western Canada to analyze factors in public perceptions and the acceptance of HF projects. Scenario attributes explicitly address the role of distributional and procedural fairness in the siting of projects together with seismicity risks modelled by a modified Mercalli intensity scale. The analysis controls for proximity and common negative environmental externalities of HF. Random effects models suggest that the notion of earthquake risks alone stands in the way of public acceptance of HF; independent of where individuals stand on the HF controversy. Affiliation with the energy industry, perceived knowledge of HF, and support for and/or concerns with different energy sources and their environmental impacts are found to shape individuals’ perceptions, including benefits and risks, and the overall acceptability of HF projects. We find this polarization to extend to (mis-)trust in different sector and policy stakeholders.

Crowdsourcing Felt Reports Using the MyShake Smartphone App

Abstract MyShake is a free citizen science smartphone app that provides a range of features related to earthquakes. Features available globally include rapid postearthquake notifications, live maps of earthquake damage as reported by MyShake users, safety tips, and various educational features. The app also uses the accelerometer in the mobile device to detect earthquake shaking, and to record and submit waveforms to a central archive. In addition, MyShake delivers earthquake early warning alerts in California, Oregon, and Washington. In this study, we compare the felt shaking reports provided by MyShake users in California with the U.S. Geological Survey’s (USGSs) “Did You Feel It?” intensity reports. The MyShake app simply asks, “What strength of shaking did you feel?” and users report on a five-level scale. When the MyShake reports are averaged in spatial or time bins, we find strong correlation with the Modified Mercalli Intensity scale values reported by the USGS based on the DYFI surveys. The MyShake felt reports can therefore contribute to the creation of shaking intensity maps.

Accuracy of Seismic Response Evaluation of Two-Dimensional Analysis Model with Rigid Joints for RC Frame Buildings.

Three- or two-dimensional (2D) numerical models are used for the evaluation of the seismic performance of reinforced concrete (RC) buildings. This study examines a 2D numerical model for a specimen used in a full-scale four-story RC shaking-table test and evaluates the accuracy of the seismic response of the 2D numerical model, which is composed of a square fiber section model for the columns, a T-shape fiber section model for the beam and slab, and a rigid joint model for the beam-column joint. A parametric analysis of the effective slab width is performed to analyze its effects on the modal shape and natural period. The results suggest that the primary natural period of the considered model is almost identical to that associated with the experimental results. The applicability of the 2D numerical model for estimating the seismic response of the structure is established. By comparing the results of the seismic analysis and the experiment in the 50% amplitude of the JMA-Kobe wave, which corresponds to slightly exceeding VII on the modified Mercalli intensity scale, the root-mean-square percentage error of the 2D numerical model is 1.03% for the floor acceleration and 4.7% for the inter-story drift. Thus, the analytical model used in this study has sufficient accuracy in evaluating the seismic performance of buildings constructed in regions with a maximum seismic intensity of VII.

LAND SURFACE CHANGES DUE TO BUKITTINGGI CITY EARTHQUAKE USING THE 2019-2020 DInSAR METHOD

Bukittinggi city is in the sink segmentation "semangko" fault line, which causes Bukittinggi City to frequently experience earthquakes. From 2019 to 2020, there have been at least 9 earthquakes above 5 on the Richter scale. DInSAR is a radar imaging method that utilizes phase, amplitude, and wavelength in its processing to obtain topography and land surface changes. This study has three aims. This research shows that the earthquake from 2019 to 2020 uses 18 pairs of sentinel-1 image scans recorded in 2019-2020 and uses DEM SRTM 30, namely the earthquake that happened on February 2, 2019, in the sub-district of Guguak Panjang with a range of 1 – 45 mm. The smallest increase occurred in the sub-district of Guguak Panjang and Mandiangin Koto Selayan, with a length of 1 mm on November 11, 2019. The most significant reduction happened in the sub-district of Aur Birugo with -22 mm. In contrast, a less substantial reduction occurred in the sub-district of Guguak Panjang with -5 mm on October 8, 2019. The Modified Mercalli intensity scale for earthquakes in 2019-2020 uses the measure of Donovan's parameters demonstrated by numbers 2, 3, and 4. Number 2 indicates that resting people feel the earthquake's strength, especially hanging, shaking, and vibrating on the second floor. Number 3 represents the vibrations of passing trucks, windows, doors, and glassware clashing and making noises

Macroseismic Intensity Re-Evaluation of the 11 June 1895 Mid-Silesia, Poland, Earthquake

Abstract Earthquakes in slowly deforming intraplate regions like Poland are not as frequent or of high intensity as at the plate boundaries. However, few low-to-moderate intensity earthquakes have been reported to have shaken different regions of Poland in the late nineteenth and early twentieth centuries. We present an intensity re-evaluation of one of these earthquakes—the 11 June 1895 Mid-Silesia, southwestern Poland earthquake. Damage reports were collected from 563 towns and villages of the Silesia region soon after the earthquake. However, these reports and the names of the places are in German. The damage reports were translated from German to English and the names of the places to present names in Polish. The intensity re-evaluation was carried out using the modified Mercalli intensity (MMI) scale. The highest intensity on the MMI scale is evaluated to be VII in two important towns of Strzelin and Ziębice. The reports mention damage to the estate officer’s house by the 11 June 1895 Mid-Silesia earthquake. In this study, the location of the estate officer’s house was determined, and suspected earthquake damage to the building was demarcated.

PRODUCTION OF ISO-INTENSITY MAP FOR THE ELAZIG EARTHQUAKE (JAN 24, 2020) USING CITIZEN COLLECTED GEODATA

Abstract. Earthquake, depending on its intensity and location of epicentre, is one of the destructive hazards. Disaster mitigation after a severe earthquake are important to minimize its detrimental effects. Nowadays, several scientific disciplines, such as biodiversity, ecology, geosciences, natural hazards etc., utilize the Citizen Science (CitSci) approaches for various purposes, since the relevant attributes can easily be provided by non-experts with mobile devices. With the CitSci method, disaster related information can be identified and provided rapidly by locals during or after a disaster. Timely, in-situ data after an earthquake can also be collected with CitSci approaches via mobile devices, which can be even more important for all countries. In addition, scientific studies on earthquakes can be enriched and accelerated by using the information provided by volunteers. By collecting reliable data with the CitSci method, the disaster mitigation efforts can be improved, and losses may be decreased. This study aims at developing a CitSci pilot project by using the data collected by volunteers (citizens) to reduce the need for field work in creating earthquake iso-intensity maps and produce them promptly. The present study was based on the 6.8 Mw Elazig earthquake occurred at 20:55 UTC on January 24th, 2020. Through the mobile application “I felt the quake”, the observations of citizens regarding the earthquake were collected. The intensities were revised from the Modified Mercalli Intensity Scale. With the help of data, an iso-intensity map was created and compared to the map produced by The Disaster and Emergency Management Presidency (AFAD), Turkey.

Correlating DYFI Data With Seismic Microzonation in the Region of Montreal

The Western Quebec seismic zone has moderate seismic activity with few historical damaging earthquakes. Nevertheless, recent risk analyses have shown that the combination of a high level of urbanization with soft soil deposits in the metropolitan area of Montreal could lead to significant damage and economic losses. Over the two decades, several projects have been completed to develop a seismic microzonation to identify zones where seismic waves could be amplified. During the same period, Natural Resources Canada developed an internet application to collect reports from the population after an earthquake and to convert them to the Modified Mercalli Intensity scale (MMI). This paper presents a first comparison of the MMI data compiled after eight recent earthquakes felt in Montreal area with the existing zonation in terms of soil classes. It shows that the MMI from individual reports increases when the observer is located in a soft soil zone. Statistics on average MMI over a regular grid confirms this trend. The numerous reports collected through the internet application, and future applications based on data collected from social media, could become a very useful source of information to complement seismic field measurements when developing and validating seismic microzonation maps.

Earthquake ground motion and human behavior: Using DYFI data to assess behavioral response to earthquakes

Human behavioral response to ground motion produced by earthquakes has been the subject of response readiness campaigns like the Great ShakeOut, conventional wisdom regarding how people respond as portrayed in news media, a small but growing social science literature and, in earlier versions of the Modified Mercalli Intensity scale, one component of the assignment of intensities to earthquakes. This study drew on the extensive USGS “Did you feel it?” (DYFI) database to explore human behavioral response in 12 earthquakes that occurred between 2005 and 2018 in 8 countries. These earthquakes varied from moderate in magnitude to very large and destructive events. Some occurred in developed nations with extensive earthquake preparedness campaigns and advanced building codes and others in developing nations with almost no attention to the hazards posed by earthquakes and no seismic provisions in building codes. Our objective was to describe and analyze the behaviors reported by those who navigated to the DYFI site and reported how they responded.

Site-specific ground motion modeling for a historical Cairo site as a step towards computation of seismic input at cultural heritage sites

Throughout time, the area of historical Cairo has been affected by several earthquakes from near and distant seismogenic zones. The maximum earthquake intensity reported in Cairo is VII, on the Modified Mercalli Intensity scale, due to the 1992 Cairo earthquake (Mw=5.9). About 212 Coptic and Islamic monuments were damaged. The spatial distribution of damage, suggests the occurrence of strong local site effects in combination with high vulnerability of the cultural heritage buildings. This study presents the application of a novel seismic hazard analysis approach at a local scale based on physics-based ground motion simulations. A site-specific multi-scenario seismic input (ground motion time histories and response spectra) is computed at a heritage building in Cairo, considering the local site effect. The seismic input is calculated in three steps: a regional scale analysis followed by a site-specific analysis and the combinations of the computed scenarios ground motion. In the regional scale analysis synthetic accelerograms are computed at the site bedrock. Then, the site-specific analysis is performed to calculate the site surface ground motions or response spectra considering the local site effect. Three earthquake scenarios have been considered, characterized by different locations, magnitudes, and fault configurations. The last step consists in the combination of the computed scenario ground motion into one single multi-scenario seismic input specific for the site of interest. This input is represented by spectral ordinates and their variability. For the engineering purpose of time history analysis, the method allows also to extract the computed site specific physics-based accelerograms, requiring no amplitude scaling nor filtering by magnitudes, distances, or site classifications, as usually done with real ground motion records.

An Earthquake Early Warning Method Based on Huygens Principle: Robust Ground Motion Prediction Using Various Localized Distance‐Attenuation Models

AbstractFor the stable operation of earthquake early warning systems under complex earthquake scenarios such as large earthquakes with complicated rupture processes and multiple simultaneous events during intense aftershock activity, wavefield‐based ground motion prediction approaches that can predict shaking directly from the observed shaking, without source parameter characterization, have been proposed. These existing algorithms, however, have weak points, including the employment of inflexible wave propagation models and limited available lead times for sites that have a potential to obtain long lead times. To address these shortcomings, I developed the Approximation by Local Pseudo‐Hypocenter Attenuation (ALPHA) method, a new wavefield‐based algorithm that predicts ground motion by estimating the distance‐attenuation relation from direct observations of the ongoing wavefield in real time. For this estimation, ALPHA uses multiple point‐source models located below each observation station to simulate elementary wave propagation in accordance with Huygens principle. Application to the 2011 Mw9.0 Tohoku‐Oki and 2016 M7.3 Kumamoto earthquakes and 21 additional earthquakes with M ≥ 7 showed that ALPHA stably calculated accurate ground motion predictions for those events and provided long lead times for sites with an intensity threshold on bedrock of three on the Japan Meteorological Agency scale (~IV–VI on the modified Mercalli intensity scale). These findings indicate that ALPHA would enable early warning systems to issue accurate warnings to wider areas at an early stage than existing algorithms.

Probable intensity of Sylhet city from an event like 1918 Srimangal earthquake

An intensity map plays an important role and is required for construction, so in this study, we presented a map of intensity for every ward of the city of Sylhet. Another objective of this research is to create a methodology to develop the intensity map for Sylhet with the equation readily available. Sylhet is Bangladesh’s most seismically susceptible region owing to its location in the southeast portion of Dauki fault. In the last 101 years, almost 184 massive earthquakes in the Sylhet area have taken place between the magnitude of 4 and 7.2. Among these earthquakes, the 1918 earthquake of Srimangal was selected as it was the first one to be felt and recorded in Bangladesh as a destructive earthquake. The probable intensity map for the Sylhet city of Bangladesh using Geographic Information Technology has been made considering the 1918 Srimangal earthquake as a scenario case. For this purpose, 157 boreholes data were collected to calculate the shear wave velocity. The SPT-N value of most of the borehole data is as deep as 15 m. Then it was converted to the required amount at a depth of 30 m. In addition, Shear wave velocity was also converted to the Peak Ground Acceleration using McGuire equation. The highest Amplification Factor was used among the three equations for converting the Peak Ground Acceleration into the Surface Acceleration. Finally, the Surface Acceleration has been converted into the Modified Mercalli Intensity scale to make it simple to comprehend. The findings show that the minimum and maximum Peak Ground Acceleration are both 0.164 g and 0.175 g, and the Amplification Factors vary between minimum and maximum from 2.027 to 3.40. Also, surface acceleration ranges from 0.347 to 0.578 g. The intensity is estimated at 27 wards in the city of Sylhet. This demonstrates that 81.48% of the intensity IX areas are impacted and 18.52% of the intensity VIII areas as a scenario case for the Srimangals 1918’s earthquake. Since the town of Sylhet does not have an intensity map, this research aims to prepare a map for all Sylhet wards.

Intensity Attenuation Model Evaluation for Bangladesh with Respect to the Surrounding Potential Seismotectonic Regimes

An effort has been made through this study to evaluate the existing intensity attenuation model (IPE) for the potential seismotectonic regimes in and around Bangladesh. To reach the goal, the seismicity of the concerned tectonic regimes has been analyzed. Apart from evaluating the appropriate intensity model, this research has also assessed the predictive performance of epicentral intensity estimation. Different magnitude types have been made uniform by converting into moment magnitude and subsequently into the Modified Mercalli Intensity scale (MMI). The epicentral intensity conversion following Li in Chinese Earthquakes (Seismological Press, Beijing, 1980) fits best for the study area among the utilized four predictive equations. The epicentral intensity conversion from the moment magnitude shows that small to moderate earthquakes get significantly overestimated. Suitable attenuation models have been applied to the different tectonic regimes based on the criteria of using the IPEs. Among all the utilized IPEs, the relation of Bakun et al. (Bull Seismol Soc Am 93:190–202, 2003) exhibits the highest standard deviation (σ = 1.61) in attenuation with distance. Although the Szeliga et al.’s (Bull Seismol Soc Am 100(2):570–584, 2010) attenuation relation has a standard deviation of 1.22, the intensity decay is little even for the greater distance (~ 800–900 km). Up to Mw 7.0, the IPE of Bindi et al. (Geophys J Int 187(1):327–337, 2011) shows realistic attenuation scenario (with σ = 1.3); however, at lower magnitude range (< Mw 7.0), the intensity starts to decay sharply. Still, the IPE of Bindi et al. (2011) is more realistic in comparison of the shakemaps of the past and in terms of convincible intensity decay with greater distance (~ 500–900 km). However, the intensity close to the epicenter gets very high MMI (XI or larger) value for the major events (Mw ≥ 8.5). Although the IPE of Chandler and Lam (J Asian Earth Sci 20(7):775–790, 2002) has distance constraints, its performance is acceptable considering the attenuation scenario with distance along with the lowest standard deviation (~ 0.92). Considering the seismic events from the only strike-slip Churachandpur Mao fault of the study area, Bakun and Wentworth (Bull Seismol Soc Am 87(6):1502–1521, 1997) relation has been applied to determine the attenuation pattern.

Characteristics of landslides triggered by the 2018 Hokkaido Eastern Iburi earthquake, Northern Japan

On 6 September 2018, a Mj 6.7 (Mw 6.6) earthquake with a focal depth of approximately 37 km and maximum seismic intensity of 7.0 on the Japan Meteorological Agency (JMA) scale (corresponding to approximately X on the Modified Mercalli Intensity (MMI) scale) struck the central and eastern Iburi regions of Hokkaido, Northern Japan, 1 day after the Typhoon Jebi passed through the region. Thousands of landslides were triggered and significant losses resulted from the earthquake sequence. A detailed landslide inventory map, including 5625 coseismic landslides, was delineated on the basis of 3307 published landslide sites. Most of the coseismic landslides are translational landslides of small to medium scale with high mobility and long run-out distance. Thirty-six people were killed by the landslides despite the afflicted area being sparsely populated. It is found that all the 5625 landslides spread in an elliptic area extending NNW/SSE, running approximately parallel to the strike of (active) faults in this region. The preferred aspect of the landslide-affected area is southerly, running nearly perpendicular to the NNW/SSE striking (active) faults. Most coseismic landslides are distributed in regions with seismic intensity of 7.0 to 8.0 (MMI Scale), with peak ground acceleration (PGA) of 0.4 to 0.7 g. Most of the coseismic landslides occurred at the elevation between 100 and 250 m, and the slope angle between 15° and 35°. Miocene sedimentary rock is the predominant bedrock type identified in the landslide area. Slope failures were triggered in stratified pyroclastic fall deposits, in the combination of strong seismic ground motion and intense antecedent precipitation. Sliding zone liquefaction phenomena were confirmed in the field investigation. The relationship between the old landslides (slope failures occurred prior to the Iburi earthquake) and the coseismic landslides is also discussed in this study.

High-Intensity Assignments for the 22 February 2011 Mw 6.2 Christchurch, Canterbury, New Zealand, Earthquake: A Contribution toward Understanding the Severe Damage Caused by This Event

ABSTRACT This article presents modified Mercalli intensity (MMI) data for the 22 February 2011 Mw 6.2 Christchurch, New Zealand, earthquake. These data include intensity levels above MMI 8 that have not been assigned previously. Two sources of data have been used in this research: GeoNet’s “Felt Classic” online questionnaires and felt reports gathered during a field study in Christchurch in February 2013. Taken together, these sets of data provided 331 valid (i.e., with all the needed information) felt reports in areas of MMI 8 or above, with 299 (90%) of the reports used to assign MMI levels above 8. This article presents a more detailed picture of the geographical damage distribution of this earthquake than has previously been available. The data differentiate damage in the center of Christchurch, with 8 communities assigned a community MMI (CMMI) of 9, 11 communities a CMMI of 10, and 8 communities a CMMI of 11, which is the maximum possible intensity in the New Zealand MMI scale, and a level of intensity not previously reported in New Zealand (Dowrick et al., 2008). The geographical damage distribution for Christchurch has been updated for intensities below MMI 8. This was done using a recently developed method that groups intensity data and allows intensities to be aggregated for a community and a single value assigned. Comparisons between MMI and peak ground velocity using the CMMI data and two ground-motion intensity correlation equations (GMICEs) indicate an underestimation of MMI when using the GMICEs and the need to review New Zealand’s GMICE.

Nowcasting earthquake damages with Twitter

The Modified Mercalli intensity scale (Mercalli scale for short) is a qualitative measure used to express the perceived intensity of an earthquake in terms of damages. Accurate intensity reports are vital to estimate the type of emergency response required for a particular earthquake. In addition, Mercalli scale reports are needed to estimate the possible consequences of strong earthquakes in the future, based on the effects of previous events. Emergency offices and seismological agencies worldwide are in charge of producing Mercalli scale reports for each affected location after an earthquake. However, this task relies heavily on human observers in the affected locations, who are not always available or accurate. Consequently, Mercalli scale reports may take up to hours or even days to be published after an earthquake. We address this problem by proposing a method for early prediction of spatial Mercalli scale reports based on people’s reactions to earthquakes in social networks. By tracking users’ comments about real-time earthquakes, we create a collection of Mercalli scale point estimates at municipality (i.e., state subdivisions) level granularity. We introduce the concept of reinforced Mercalli support, which combines Mercalli scale point estimates with locally supported data (named ‘local support’). We use this concept to provide Mercalli scale estimates for real-world events by providing smooth point estimates using a spatial smoother that incorporates the distribution of municipalities in each affected region. Our method is the first method based on social media that can provide spatial reports of damages in the Mercalli intensity scale. Experimental results show that our method is accurate and provides early spatial Mercalli reports 30 minutes after an earthquake. Furthermore, we show that our method performs well for earthquake spatial detection and maximum intensity prediction tasks. Our findings indicate that social media is a valuable source of spatial information for quickly estimating earthquake damages.

On the Devastating Earthquake at the Iran–Iraq Border

The process of the lead up and development of a catastrophic seismic event that affected the Earth’s crust and the upper mantle, which led to a change in the natural environment in the western part of the Zagros folded mountain belt, is analyzed. The macroseismic effect, the focal mechanism, the aftershock sequence, the seismotectonic position of the epicentral area, and other parameters characterizing the features of the zone of this catastrophic earthquake with magnitude М = 7.4 that occurred near the Iran–Iraq border on November 12, 2017, are described. In one settlement (Iraq, the city of Dzharband khan), a macroseismic effect corresponding to 9-points according to the Modified Mercalli Intensity scale is recorded. An area of about 150 × 100 km2 underwent impacts of 7–8 points, tremors with the intensity of 5–6 points covered an extensive area of about 800 × 700 km2, and 4- to 5-point impacts were observed all over western Iran and eastern Iraq and appeared in major cities such as Tehran, Baghdad, Kirkuk, Ahvad, and Pasht. In the period from November 12, 2017, until January 21, 2018, more than 50 aftershocks with magnitude mb = 4.2–5.6 were registered in the epicenter zone of the earthquake according to data from the Federal Research Center Geophysical Survey of the Russian Academy of Sciences (RAS). Their epicentral area extended in the near-meridional direction along the Iraq–Iran border, primarily to the south from the epicenter of the main shock. Its length reached about 210 km and width was about 60 km. The position of the epicentral field of the aftershocks makes it possible to associate the earthquake focus of November 12, 2017, with the Khanaqin fault zone of the meridional strike and dextral strike-slip kinematics. The fault crosses Zagros diagonally near the Iran–Iraq border. Given that the size of the earthquake focus is established by the distribution of epicenters of the aftershocks, it covered the Khanaqin fault zone almost over its entire length. Sufficient attention is paid to the identified prognostic effects. The data of observations from geophysical observatories reflecting the processes of earthquake lead up and development are presented. Before the earthquake of November 12, 2017, the information and measuring systems of the North Caucasus geophysical observatory of Schmidt Institute of Physics of the Earth, RAS, had recorded gravitomagnetic disturbances of the ultralow frequency range. These prognostic effects appeared a few hours before the main shock. The conditions of the origination and development of seismogravity and gravitomagnetic disturbances are specified. In light of the presented material, it becomes clear that the experimental study of a separate class of fundamental gravitomagnetism problems identified in recent years is a defining problem of geophysics today. The gravitomagnetic disturbances in the lithosphere and other geospheres of the Earth recorded at large distances from the focal area can be considered a source of information on the time of appearance of the main high-magnitude shock. To use these effects for a real prediction of the expected magnitude and location and time of the pending earthquake, it is apparently necessary to develop a monitoring network at the observatory equipped with specialized measuring systems that can detect weak gravitomagnetic and seismogravity signals in the high-interference signaling environment on the Earth.

Surface Level Synthetic Ground Motions for M7.6 2001 Gujarat Earthquake

The 2001 Gujarat earthquake was one of the most destructive intraplate earthquakes ever recorded. It had a moment magnitude of M w 7.6 and had a maximum felt intensity of X on the Modified Mercalli Intensity scale. No strong ground motion records are available for this earthquake, barring PGA values recorded on structural response recorders at thirteen sites. In this paper, synthetic ground motions are generated at surface level using the stochastic finite-fault method. Available PGA data from thirteen stations are used to validate the synthetic ground motions. The validated methodology is extended to various sites in Gujarat. Response spectra of synthetic ground motions are compared with the prescribed spectra based on the seismic zonation given in the Indian seismic code of practice. Ground motion characteristics such as peak ground acceleration, peak ground velocity, frequency content, significant duration, and energy content of the ground motions are analyzed. Response spectra of ground motions for towns situated in the highest zone, seismic zone 5, exceeded the prescribed spectral acceleration of 0.9 g for the maximum considered earthquake. The response spectra for towns in seismic zone 5 exhibit peaks in the low period ranges, indicating high vulnerability of low rise structures designed as per the provisions of the Indian seismic code of practice. The response spectra for towns situated in seismic zone 3 were considerably lower than the prescribed maximum spectral acceleration of 0.4 g. The substantial damage reported in towns situated in seismic zone 3 is due to poor construction practices and non-compliance with provisions of seismic design standards.

Statistical model for earthquake economic loss estimation using GDP and DPI: a case study from Iran

As earthquakes can result in multi-dimensional negative consequences such as human loss and building damage, the ability to make accurate economic loss estimations immediately after the occurrence is crucial. Unfortunately, in many earthquake-stricken countries such as Iran, governments are often unable to quickly or accurately assess post-earthquake losses. The aim of this paper, therefore, is to extend the model developed by Chan et al. (Nat Hazards 17:269–283, 1998) to two independent variables to develop an earthquake economic loss estimation method based on the economic and socio-economic indices gross domestic product (GDP) and disposable personal income (DPI) and a seismic hazard probability function. A global cell map is also considered to assess the GDP and DPI based on the population in each cell affected by the earthquake. In the final stage, using the Modified Mercalli Intensity Scale, 18 earthquake damaged areas in Iran are taken as case study to estimate the economic losses using the new model presented in this paper.