Modified Mercalli Research Articles

Earthquake Environmental Effects of the 1992 MS7.3 Suusamyr Earthquake, Kyrgyzstan, and Their Implications for Paleo-Earthquake Studies

Large pre-historical earthquakes leave traces in the geological and geomorphological record, such as primary and secondary surface ruptures and mass movements, which are the only means to estimate their magnitudes. These environmental earthquake effects (EEEs) can be calibrated using recent seismic events and the Environmental Seismic Intensity Scale (ESI2007). We apply the ESI2007 scale to the 1992 MS7.3 Suusamyr Earthquake in the Kyrgyz Tien Shan, because similar studies are sparse in that area and geological setting, and because this earthquake was very peculiar in its primary surface rupture pattern. We analyze literature data on primary and secondary earthquake effects and add our own observations from fieldwork. We show that the ESI2007 distribution differs somewhat from traditional intensity assessments (MSK (Medvedev-Sponheuer-Karnik) and MM (Modified Mercalli)), because of the sparse population in the epicentral area and the spatial distribution of primary and secondary EEEs. However, the ESI2007 scale captures a similar overall pattern of the intensity distribution. We then explore how uncertainties in the identification of primary surface ruptures influence the results of the ESI2007 assignment. Our results highlight the applicability of the ESI2007 scale, even in earthquakes with complex and unusual primary surface rupture patterns.

Reversible ground motion-to-intensity conversion equations based on the EMS-98 scale

The relation between observed macroseismic intensities and recorded ground motion parameters is a matter of interest in earthquake engineering, and it has been widely discussed in literature in the past. Several relationships already exist, correlating macroseismic intensity and peak ground motion parameters (i.e. PGA, PGV or PGD, respectively peak ground acceleration, velocity and displacement). However, most of these formulations are based on Mercalli-Cancani-Sieberg (MCS) scale, developed using regional databases and difficult to be applied at large scale. In this research, new formulations are proposed that correlate European Macroseismic Scale (EMS-98) with ground shaking parameters (PGMs), Arias intensity and Housner intensity. An initial PGM/EMS-98 intensity dataset was assembled for this scope, collecting 610 data pairs of observations, from 35 different Italian seismic events derived from the Parametric Catalogue of Italian Earthquakes (CPTI15) and the Italian Accelerometric Archive (ITACA), subsequently filtered considering only tectonic events and data pairs with site – station distances lower than 3 km. The resulting final dataset of 220 data pairs from 22 earthquakes was thus used to obtain regression relationships, finally compared with existing models based on the Modified Mercalli (MM) scale and MCS scale.

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.

Earthquake Macro-zonation Based Peak Ground Acceleration, Modified Mercalli Intensity, And Type of Rocks around Matano Fault

This study aims to determine earthquake vulnerable zones. We conducted research on earthquake macro-zonation based on PGA, Modified Mercalli Intensity (MMI), and type of rocks around Matano Fault in the area of 1.60 S to 2.990 S and 120.50 E to 122.470 E. We have acquired Maximum PGA and Modified Mercalli Intensity (MMI) for each observation point on the ground from the four major earthquake events. The empirical model is used due to lack of acceleration data recorded. We tried some empirical methods, but the McGuire method is found to be acceptable for this area. The result gives the maximum variation of PGA which is ranged between 18.40 - 363.54 gals. While the variation of MMI using empirical Wald attenuation gives values ranging from 2.9 - 7.7 MMI. The most vulnerable zone is located around Sorowako city with PGA value of 326.55 gals and MMI value of 7.5 MMI. This area is between ultra-basic rock and metamorphic rock formation. The vulnerable zone is near largest earthquake 6.2 M on 15-02-2011.

Earthquake and resultant apocalypse of Shimla city

Vulnerability of cities largely depends upon rising population, its unchecked constructional growth and failure in lifeline infrastructure. Shimla city lying in the lapse of Western Himalayas was founded by the British in the early 19th century. The region is seismically active and lies in Zone IV of India with modified Mercalli (MM) intensity scale of VIII and peak ground acceleration (PGA) of 4.0 metres per second squared. The objective of this conceptual and empirical research paper is to evaluate Shimla city's earthquake vulnerability with regard to past and present scenario of infrastructures within it, supported by local residents' perspective. This study sought out the awareness of seismicity among the residents of Shimla, their opinion and knowledge, related to earthquake resistant houses, lifeline structures, earthquake measures and trust in city authorities. The comparison between primary data and available secondary data is indicative of the high seismic vulnerability levels and concludes with suggestions, for both authorities and residents of Shimla city.

Earthquake and resultant apocalypse of Shimla city

Vulnerability of cities largely depends upon rising population, its unchecked constructional growth and failure in lifeline infrastructure. Shimla city lying in the lapse of Western Himalayas was founded by the British in the early 19th century. The region is seismically active and lies in Zone IV of India with modified Mercalli (MM) intensity scale of VIII and peak ground acceleration (PGA) of 4.0 metres per second squared. The objective of this conceptual and empirical research paper is to evaluate Shimla city's earthquake vulnerability with regard to past and present scenario of infrastructures within it, supported by local residents' perspective. This study sought out the awareness of seismicity among the residents of Shimla, their opinion and knowledge, related to earthquake resistant houses, lifeline structures, earthquake measures and trust in city authorities. The comparison between primary data and available secondary data is indicative of the high seismic vulnerability levels and concludes with suggestions, for both authorities and residents of Shimla city.

Strong ground motion simulation for the 2013 Lushan MW6.6 earthquake, Sichuan, China, based on the inverted and synthetic slip models

It is well known that quantitative estimation of slip distributions on fault plane is one of the most important issues for earthquake source inversion related to the fault rupture process. The characteristics of slip distribution on the main fault play a fundamental role to control strong ground motion pattern. A large amount of works have also suggested that variable slip models inverted from longer period ground motion recordings are relevant for the prediction of higher frequency ground motions. Zhang et al. (Chin J Geophys 56:1412–1417, 2013) and Wang et al. (Chin J Geophys 56:1408–1411, 2013) published their source inversions for the fault rupturing process soon after the April 20, 2013 Lushan earthquake in Sichuan, China. In this study, first, we synthesize two forward source slip models: the value of maximum slip, fault dimension, size, and dimension of major asperities, and corner wave number obtained from Wang’s model is adopted to constrain the generation of k−2 model and crack model. Next, both inverted and synthetic slip models are employed to simulate the ground motions for the Lushan earthquake based on the stochastic finite-fault method. In addition, for a comparison purpose, a stochastic slip model and another k−2 model (k−2 model II) with 2 times value of corner wave number of the original k−2 model (k−2 model I) are also employed for simulation for Lushan event. The simulated results characterized by Modified Mercalli Intensity (MMI) show that the source slip models based on the inverted and synthetic slip distributions could capture many basic features associated with the ground motion patterns. Moreover, the simulated MMI distributions reflect the rupture directivity effect and the influence of the shallow velocity structure well. On the other hand, the simulated MMI by stochastic slip model and k−2 model II is apparently higher than observed intensity. By contrast, our simulation results show that the higher frequency ground motion is sensitive to the degree of slip roughness; therefore, we suggest that, for realistic ground‐motion simulations due to future earthquake, it is imperative to properly estimate the slip roughness distribution.

The recording of floods and earthquakes in Lake Chichój, Guatemala during the twentieth century

Laguna Chichoj (Lake Chichoj) is the only deep permanent lake in the central highlands of Guatemala. The lake is located in the boundary zone between the North American and Caribbean plates. The lake has been struck by devastating earthquakes and tropical cyclones in historical times. We investigated the imprint of twentieth century extreme events on the sedimentary record of this tropical lake using a bathymetric survey of the lake, coring the lake floor, and providing a chronology of sediment accumulation. The lake occupies a series of circular depressions likely formed by the rapid dissolution of a buried body of gypsum. 210Pb and 137Cs inventories and varve counting indicate high rates of sedimentation (1–2 cm year−1). The annually layered sediment is interrupted by turbidites of two types: a darker-colored turbidite, enriched in lake-derived biogenic constituents, and interpreted as a seismite, and a lighter-colored type, enriched in catchment-derived constituents, interpreted as a flood layer. Comparison of our 137Cs-determined layer ages with a catalog of twentieth century earthquakes shows that an earthquake on the Motagua fault in 1976 generated a conspicuous darker-colored turbidite and slumped deposits in separate parts of the lake. The entire earthquake inventory further reveals that mass movements in the lake are triggered at Modified Mercalli Intensities higher than V. Tropical cyclonic depressions known to have affected the lake area had limited effect on the lake, including Hurricane Mitch in 1998. One storm however produced a significantly thicker flood layer in the 1940s. This storm is reportedly the only event to have generated widespread slope failures in the lake catchment. It is thus inferred that abundant landsliding provided large amounts of concentrated sediment to the lake, through hyperpycnal flows.

Earthquake hazard of dams along the Mekong mainstream

In this study, the earthquake hazard was evaluated for all of 19 of the proposed or built dams along the Mekong River. All values representing a potential indication of hazardous earthquakes, such as the closest earthquake and seismogenic faults and including the seismic parameters required for a seismic safety evaluation, were clarified. The results will be useful in reviewing the safety of existing dams and for the design of suitable earthquake resistant specifications for any currently or future planned dam construction in this area. Seismotectonically, 14 of the 19 proposed Mekong River dams are located within an earthquake source zone. Most of faults are potentially still active, according to both seismicity and paleoseismological evidence. In addition, the maximum credible earthquakes were estimated to be in the range of 7–8 Mw for the closest fault zone of each dam. Previous isoseismal maps indicated a risk of shaking intensities of around scale III–IV (Modified Mercalli Intensity Scale) for the dams. According to the preliminary ranging of the International Commission on Large Dams, 9 of these 19 dams are classified as in an extreme hazard class and so need careful observation and monitoring of hazardous earthquakes. An effective mitigation plan should also be prepared for each operating dam.

Maximum macroseismic intensity map of Greece for the time period 1953–2011

The aim of this paper is to present the spatial distribution of macroseismic intensities assigned in modified Mercalli (MM) scale, across the Greek territory. For this purpose, a digital database with more than 30,000 local seismic intensity recordings from 156 major earthquake events that affected Greece and adjacent areas during the period 1953–2011 was developed. These events have focal depths up to about 150 km and surface-wave magnitudes (Ms) greater than 4.4. Various GIS-based techniques for data analysis and map creation were applied. A number of seismic intensity maps have been produced taking into account different attributes like intensities for shallow or deep events, maximum intensities by administrative units, maximum intensity for significant earthquakes, etc. The main map produced is the national map of maximum seismic intensities for shallow earthquakes (scale 1:1.500.000). The final layout also contains the maximum seismic intensities for deep earthquakes, the tectonic lines of Greece, the earthquakes of the database as well as the seismic intensities for two significant earthquakes in the last six decades.

Influence of epicentral distance on local seismic response in Kolkata City, India

The influence of source and epicentral distance on the local seismic response in the Kolkata city is investigated by computing the seismic ground motion along 2-D geological cross-sections in the Kolkata city for the earthquake that occurred on 12 June 1897 (M w = 8.1; focal mechanism: dip = 57°, strike = 110° and rake = 76°; focal depth = 9 km) in Shillong plateau. For the estimation of ground motion parameters, a hybrid technique is used, which is the combination of modal summation and finite difference method. This technique allows the estimation of site specific ground motion for various events located at different distances from Kolkata city, taking into account simultaneously the position and geometry of the seismic source, the mechanical properties of the propagation medium and the geotechnical properties of the site. The epicenter of the Shillong earthquake is about 460 km away from Kolkata. The estimated peak ground acceleration (PGA) varies in the range of 0.11–0.18 g and this range corresponds to the intensity of IX to X on the Mercalli-Cancani-Sieberg (MCS) scale and VIII on the Modified Mercalli (MM) scale. The maximum amplification in terms of response spectral ratio (RSR) varies from 10 to 12 in the frequency range 1.0–1.5 Hz. These amplifications occur in correspondence to low-velocity shallow, loose soil deposit. The comparison of these results with earlier ones obtained considering the Calcutta earthquake that occurred on 15 April 1964 (M w = 6.5; focal mechanism: dip = 32°, strike = 232° and rake = 56°; focal depth = 36 km) shows that the source parameters (magnitude and focal mechanism) and epicentral distance play an important role on site response but the variation in the frequency of the peak values (RSR) is negligible. The obtained results match with observed reported intensities in Kolkata region.

Oldest ‘earthquake’ in South Africa (Robben Island, 07 April 1620) discredited

The oldest recorded earthquake in South Africa is widely accepted (in several seismic catalogues) to have occurred on 07 April 1620. This earthquake was regarded as having a Modified Mercalli Scale intensity of II-IV, corresponding to a Richter Scale Magnitude of ~4. An examination of the original sources on which the record of this earthquake rests, reveals that it was based on a description of 'two startling thunderclaps like cannon shots while ship was becalmed near Robben Island' by Augustin de Beaulieu, who was the head of a fleet of three ships which put in Table Bay in March-April 1620. A full excerpt of Beaulieu's account reveals that the thunderclaps took place in a short period of calm during an extended period of stormy weather, and that the observations were made on board ship, so that no seismic ground vibration was felt. The Western Cape has a much lower incidence of lightning than the interior of South Africa, and the fact that the thunderclaps were not accompanied by lightning is not unusual. Thus the simplest explanation of the thunderclaps is that they were the result of atmospheric phenomena, and not a result of seismic activity, as interpreted by J.N. Theron in 1974. The events of 07 April 1620 should thus be removed from the catalogues of historical seismicity in South Africa, making the slight shock felt in Cape Town in 1690, with a Modified Mercalli Scale intensity of III, the oldest recorded seismic tremor in the history of South Africa.

Cumulative Absolute Velocity (CAV) and Seismic Intensity Based on the PEER-NGA Database

Cumulative absolute velocity (CAV) has been proposed as an instrumental index to quantify the potential earthquake damage to structures. We explore this idea further by developing a relationship between the standardized version of CAV and the Japan Meteorological Agency (JMA) and modified Mercalli (MMI) instrumental seismic intensities in order to correlate standardized CAV with the qualitative descriptions of damage in the corresponding macroseismic intensity scales. Such an analysis statistically identifies the threshold values of standardized CAV associated with the onset of damage to buildings of good design and construction inherent in these scales. Based on these results, we suggest that CAV might be used to rapidly assess the potential damage to a general class of conventional structures after an earthquake. However, other ground motion or damage-related parameters might be better suited to quantifying the potential damage to structures of a specific type and size.

The Darfield (Canterbury, New Zealand) Mw 7.1 Earthquake of September 2010: A Preliminary Seismological Report

At 04:35 on Saturday 4 September 2010 local time (16:35 on 3 September UT) a moment magnitude ( Mw ) 7.1 earthquake struck approximately 10 km southeast of the town of Darfield and within 40 km of New Zealand's second largest city, Christchurch, causing extensive damage in the city and surrounding region. There was no loss of life due to a fortunate combination of strict building codes and the earthquake occurring at 04:35 local time when the streets were largely empty, but about 100 people were injured (two seriously) and many more were made homeless, at least temporarily. Current estimates put the total cost of repairs at NZ $4 billion (about US $3 billion). The key seismological features of the Darfield earthquake are summarized in Table 1. The epicenter and depth are very well constrained by the large number of nearby seismograph and strong-motion accelerometer sites (Figure 1). A surface rupture consistent with strike-slip faulting was quickly identified about 4 km south of the epicenter on a previously unknown fault, which has been named the Greendale fault, although various geophysical data sets have shown that the overall rupture process is more complex. View this table: TABLE 1 The Key Seismological Features of the Darfield Earthquake Modern buildings in Christchurch performed very well in the earthquake, but many older brick and masonry buildings were badly damaged. Liquefaction and the associated lateral spreading and slumping caused extensive damage, even to new buildings, in areas near the coast with sandy soils (Cubrinovski and Green 2010). The earthquake was felt throughout the entire South Island and a large part of the North Island at distances greater than 900 km, with the maximum felt intensity estimated to be Modified Mercalli (MM) 9. Measured accelerations near source exceeded 1 g with several reading well over 0.5 g. A feature of the …

Spatial distribution of ground shaking in characteristic earthquakes on the Wellington and Alpine faults, New Zealand, estimated from a distributed-source model

A distributed-source model, recently developed by the authors, was used to study the spatial distribution of Modified Mercalli (MM) intensities and peak ground accelerations (PGA) in characteristic earthquakes, of Mw7.5 and 8.1 respectively, on the 75 km long Wellington fault and the 413 km long Alpine fault. In each event the predicted intensities reach MM10 and the PGAs reach 0.8g near the fault trace over much of its length, varying along it depending on the location of asperities. PGAs are related to MM intensity using a quadratic expression derived using New Zealand data. Comparisons are made between the PGA patterns estimated indirectly from the distributed-source MM intensity model and those estimated directly from a PGA model, which defines site-source distance as the shortest distance from the site to the fault. There are many similarities and some differences, the latter being attributable largely to the different methods of measuring site-to-source distances. Finally selected seismic risk issues for people and the built environment, including lifelines, are considered for Alpine fault earthquakes.

Felt Earthquake Reporting via the Internet in New Zealand

New Zealand felt earthquake reports have been collected since the late 19th century. In March 2004, the GeoNet Project, operated by GNS Science, implemented an Internet-based questionnaire. The aim was to provide an objective and automatic assignment of Modified Mercalli (MM) earthquake shaking intensity and location based on answers to a set of standardized questions. Since the first year of implementation, the number of reports received has increased tenfold. Besides providing valuable information for emergency response agencies, the reports led to the enhancement of isoseismal models and better understanding of the regional effects of earthquakes in New Zealand. The GeoNet Project, launched in 2001, is an integrated geological hazards monitoring and data collection system funded by the New Zealand Earthquake Commission and designed, built, and operated by GNS Science. GeoNet provides real-time monitoring of earthquake, volcano, land deformation, tsunami, and landslide hazards in New Zealand. The networks of instruments collect data that are freely available to users both in New Zealand and around the world via its Web site (http://www.geonet.org.nz). ### History of Electronic Felt Earthquake Reporting Felt earthquake reports are a valuable means of obtaining information on how people across New Zealand have experienced an earthquake. Reports have been collected in New Zealand since the late 19th century. Increasingly inexpensive technology and the growing public adoption of the Internet has fueled three phases of electronic felt report collection in the past ten years: ### Optical Mark Recognition (OMR) Forms A machine-readable questionnaire, developed by G. Downes and D. Maunder in 2000, was an entirely revised and expanded set of questions based on Dowrick's (1996) version of the Modified Mercalli Intensity scale. The new form had not been widely implemented before it became clear that the growing use of the Internet by the general public suggested a more effective means of obtaining …

A distributed-source approach to modelling the spatial distribution of MM intensities resulting from large crustal New Zealand earthquakes

This paper presents a new approach to modelling the spatial distribution of intensities in crustal earthquakes, using a distributed source. The source is represented by one or two rectangular fault rupture planes of chosen dip, discretised into small rectangles each with its own share of the total seismic moment, and modelling chosen distributions of asperities. The Modified Mercalli (MM) intensity of shaking is represented by isoseismals. Comparisons are made with the actual isoseismals (particularly of intensities MM9 and MM10) of selected large historical crustal New Zealand earthquakes and those predicted by the simpler models of Dowrick & Rhoades (2005). Important differences and insights are found regarding near-source spatial distributions of ground shaking of shallow earthquakes with rupture length greater than about 28 km (Mw > 6.8) with any dip, and for Mw > c. 5.5 with dip < 60º. The influence of asperities relative to that of non-asperities is seen as modest near-fault increases in intensity. The new model can be applied to planar or biplanar fault ruptures of any length, width and dip. In the absence of isoseismal data on large earthquakes with normal focal mechanisms the current model is only verified for use on strike-slip and reverse events. A new concept, seismic-source intensity, is introduced and utilized.
 The new model can also be applied to earthquakes in other regions of the world with adjustments for local attenuation rates as necessary.

Influence of Rivera-Cocos Plate Boundary Geodynamics on Earthquake Intensity Patterns: the 9 October 1995 (Mw 8.0) and 21 (22) January 2003 (Mw 7.5) Earthquakes

This study examines two large thrust subduction earthquakes occurring within the Rivera-Cocos plate boundary which struck the western coast of Mexico on 9 October 1995, Mw 8.0, and 21 (22 GMT) January 2003, Mw 7.5. The Modified Mercalli (MM) earthquake intensities observed during these earthquakes were surprising for some towns located in the Mexican coastal zone. During the smaller Mw 7.5 2003 earthquake, MM intensity VII was observed for towns of Colima, Villa de Alvarez and Ixtlahuacan, while during the larger Mw 8.0 1995 earthquake, their MM intensities were only IV–V, V and V–VI, respectively. We construct the macroseismic patterns for these two earthquakes and discuss the possible reasons for the significant difference in the outline of the MM VII isoseismals, such as the tectonic setting of epicentral zones and the directivity of rupture processes along and across the coastal line.

Probabilistic seismic hazard assessment in Greece – Part 1: Engineering ground motion parameters

Abstract. Seismic hazard assessment represents a basic tool for rational planning and designing in seismic prone areas. In the present study, a probabilistic seismic hazard assessment in terms of peak ground acceleration, peak ground velocity, Arias intensity and cumulative absolute velocity computed with a 0.05 g acceleration threshold, has been carried out for Greece. The output of the hazard computation produced probabilistic hazard maps for all the above parameters estimated for a fixed return period of 475 years. From these maps the estimated values are reported for 52 Greek municipalities. Additionally, we have obtained a set of probabilistic maps of engineering significance: a probabilistic macroseismic intensity map, depicting the Modified Mercalli Intensity scale obtained from the estimated peak ground velocity and a probabilistic seismic-landslide map based on a simplified conversion of the estimated Arias intensity and peak ground acceleration into Newmark's displacement.

The intracratonic Caraíbas–Itacarambi earthquake of December 09, 2007 (4.9 mb), Minas Gerais State, Brazil

On December 9, 2007, a 4.9 m b earthquake occurred in the middle of the São Francisco Craton, in a region with no known previous activity larger than 4 m b. This event reached intensity VII MM (Modified Mercalli) causing the first fatal victim in Brazil. The activity had started in May 25, 2007 with a 3.5 magnitude event and continued for several months, motivating the deployment of a local 6-station network. A three week seismic quiescence was observed before the mainshock. Initial absolute hypocenters were calculated with best fitting velocity models and then relative locations were determined with hypoDD. The aftershock distribution indicates a 3 km long rupture for the mainshock. The fault plane solution, based on P-wave polarities and hypocentral trend, indicates a reverse faulting mechanism on a N30°Ε striking plane dipping about 40° to the SE. The rupture depth extends from about 0.3 to 1.2 km only. Despite the shallow depth of the mainshock, no surface feature could be correlated with the fault plane. Aeromagnetic data in the epicentral area show short-wavelength lineaments trending NNE–SSW to NE–SW which we interpret as faults and fractures in the craton basement beneath the surface limestone layer. We propose that the Caraíbas–Itacarambi seismicity is probably associated with reactivation of these basement fractures and faults under the present E–W compressional stress field in this region of the South American Plate.