Macroseismic Parameters Research Articles

A SERIES of TANGIBLE EARTHQUAKES in 2018–2019 in the FOCAL ZONE of the 10-point SPITAK EARTHQUAKE of 1988

The paper presents the results of a study of 2018–2019 tangible seismic events with intensity at the epicenter of 5–6 points and above, that occurred in the focal zone of the 10-point Spitak earthquake of 07.12.1988 with MLH =6.8. Two earthquakes of June 6, 2018, with МL=3.6 and МL=4.3, as well as two shocks on September 10, 2019, with МL=4.7 and with МL=3.9, were felt in the nearest settlements with an intensity of 5 or more points. For three of them, according to the collected macroseismic data, isoseist maps were constructed and macroseismic parameters were determined. The strike of the nodal planes in the earthquake sources is consistent with the direction of elongation of the isoseist system, which, in turn, for three events coincides with the strike of the nearest faults of the Pambak-Sevan system.

Earthquakes Parameters from Citizen Testimonies: A Retrospective Analysis of EMSC Database

Abstract We aim to compute macroseismic parameters (location and magnitude) using the BOXER code for the first time on the citizen testimonies, that is, individual intensity data points (IDPs) at the global scale collected and made available by the LastQuake system of the European–Mediterranean Seismological Centre (EMSC). IDPs available for different earthquakes are selected to eliminate those that are geographically inconsistent with most data; then they are clustered spatially based on various methods. For each cluster with at least three IDPs, a macroseismic data point (MDP), corresponding to an intensity value assessed for given localities as in classical macroseismic studies, is computed by various central tendency estimators (average, median, and trimmed averages). Finally, macroseismic parameters are obtained by MDP distribution using two location methods of BOXER code. For each earthquake, we used raw and corrected intensities and 132 different combinations of grouping methods, estimators, and BOXER methods. We assigned a ranking to the combinations that best reproduce instrumental parameters and used such a ranking to select preferred combinations for each earthquake. We analyzed retrospectively the reliability of the parameters as a function of time and space. The results are essentially identical using original and corrected intensities and show higher reliability for BOXER’s method 1 than for method 0; they are dependent on the geographical area, and generally improve over time and with the number of IDPs collected. These findings are useful for the future real-time analyses, and for evaluating the location and magnitude of earthquakes whenever a sufficient number of IDPs are available and with a distribution such that MDPs can be derived and the BOXER method applied.

Modulation of Seismic Radiation by Fault-Scale Geology of the 2016 Mw 6.0 Shallow Petermann Ranges Earthquake (PRE) in Central Australia

ABSTRACTUnderstanding the modulatory influence of fault-scale geology on seismic behavior of earthquake faults is central to determining the physics of faulting and seismic hazard analysis. Although laboratory experiments predict that seismic parameters can be modulated by fault-scale geology, there is scant empirical evidence of this process at field scale due largely to a lack of shallow earthquakes of which causative faults can be mapped to known bedrock structure. The 20 May 2016 Mw 6 Petermann Ranges earthquake (PRE) is the best-recorded continental event in Australia to date, and it is an excellent candidate to investigate the possible link between seismic parameters and fault-scale geology as its causative fault has previously been linked to known bedrock structure using distributions of aftershocks, surface observations, and geophysical mapping. In this study, we analyze strain energy partitioning of PRE by determining seismic radiation efficiency (0.31) and apparent stress (0.34 MPa) together with previously estimated stress drop (2.2 MPa) and find that the combination of these macroseismic parameters deviates from that expected of a shallow immature fault in intraplate continental regions typically characterized by large recurrence intervals. It instead appears to have mimicked a mature fault, which we attribute to the characteristics of the causative fault confined to mechanically weaker, phyllosilicate-rich foliations of the bedrock that have anomalously lower fracture energy. Therefore, PRE rupture suggests the presence of a spectrum of shallow (<20 km) fault slip behavior modulated by fault-scale geology.

GAZORCHASHMA EARTHQUAKE on July 1, 2016 with KR=12.5, Mw=5.0, I0=6–7 (Tajikistan)

The field survey results of the consequences of July 1, 2016 earthquake that occurred on the territory of the Rasht (Garm) district of the Republic of Tajikistan are presented. An analysis of damage to buildings and structures is made and their main reasons are revealed. The intensity map is composed and macroseismic parameters are determined. As result of the complex analysis of the main shock focal mechanism, the aftershocks and faults location, the confinement of the earthquake to the main geological structures of the region is established.

KARAMYK EARTHQUAKE of May 3, 2017 with KR=14.2, Мs=6.0, I0=7 (Тajikistan)

The results of field survey of consequences of the May 3, 2017 earthquake are presented. The isoseismal map is created, the earthquake macroseismic parameters are determined and their connection with geological structures is established. The analysis of damage for buildings and constructions is made.

Earthquakes of 1838 and 1839 in the Slovene Hills (Slovenia)-Međimurje (Croatia) area

Analyses of available data (newspaper reports, historical and church chronicles, chronical earthquake overviews, travel books, monographies, research papers, etc.) on effects of the earthquakes that shook the greater Ormož area at the Slovenian-Croatian border in the 1838 and 1839 revealed that one of them, recorded in a number of regional and global catalogues, is in fact a fake - the earthquake of 26 August 1838 never happened. This error creeped into various reports and studies, and then into many relevant catalogues, so this event should by systematically erased from the catalogues used to estimate seismicity rates in the neighbourhoods of north-western Croatia, north-eastern Slovenia, and south-western Hungary.Regarding the earthquake of 31 July 1838, we used important new sources of information that have not been consulted in any previous study. This made inversion of macroseismic parameters more robust. Our estimates of the macroseismic moment magnitude (Mwm = 4.8) is mostly higher than the values reported in the available catalogues. Reliable information on the effects of the smaller event of 22 March 1839 were found for two localities only, so its epicentre was placed into the town of Ormož where the maximum intensity was observed. Its estimated moment magnitude (Mwm) is close to the median of values found in the six consulted catalogues that listed this event.The macroseismic epicentre of the 1838 earthquake lies close to the junction of surface traces of the Donat strike-slip fault and the reverse Čakovec fault. Based on their assumed geometry and the location of the macroseismic hypocentre, we give slight preference to the Donat fault as the seismogenic source.

Visualization of macroseismic parameters during examination of epicentral zones of strong earthquakes

The article discusses the fragile destruction of building materials during strong earthquakes, the features of the macroseismic effect of cracking expressed in the protective coatings of buildings; it is recommended to optimize the composition based on polymer by composition that increases the crack resistance of plaster solutions. In particular, the visualization of macroseismic parameters is given on the example of the survey of the epicentral zones of the Tashkent (2008), Cannes (2011) and Marzhanbulak (2013) strong earthquakes that occurred in Kyrgyzstan and Uzbekistan. Possible directions of crack development and density of their distribution over the macroseismic area are analyzed. It was revealed that the vulnerability to micro-destruction of types of protective materials is proportional to the seismic intensity and is mainly due to the intensity of seismic vibrations.

Short note on the contribution of newspapers and periodicals of the nineteenth and twentieth centuries to the discovery of new historical earthquakes in Algeria

A great number of local newspapers and periodicals of the nineteenth and twentieth centuries contributed to the survival of information related to the earthquakes that occurred in Algeria during those periods. These documents which often relay the information from official institutions provide fruitful seismological accounts allowing a sound reappraisal of Algeria seismicity in terms of the estimation of macroseismic parameters. A recent systematic documentation on the Algeria seismicity revealed the occurrence of more than 650 earthquakes that were not reported in the previous seismological compilations, from 1844 onward, despite their significant number. In this paper we provide a quick overview on the newspapers and periodicals that existed at that time and from which fruitful information were retrieved and focus on the most significant events that we newly found. A careful analysis of the historical records allowed the estimation of the intensity of these earthquakes, which globally ranges from V to VIII EMS. These new results augment the seismological knowledge in Algeria and will certainly have implications for seismic hazard assessment.

Определение параметров исторических землетрясений по макросейсмическим данным

The paper attempts to determine the main parameters of historical earthquakes of the Carpathian region based on macroseismic data, using the macroseismic field equation, indirect parameters, and complex comparison with modern earthquakes. So far, the main source of information about the parameters of historical earthquakes in the Carpathian region has been "New catalog of strong earthquakes ...". In this catalog, all parameters are defined very ap-proximately, with a wide range of values. In addition, over the forty-year period since the release of the catalog, the initial macroseismic data of Carpathian region earthquakes have been substantially replenished and re-evaluated using the MSK-64 macroseismic scale. The study determined such basic parameters of historical earthquakes as the macroseismic epicenter, the intensity at the epicenter, focal depth, and magnitude. As well as additional parameters: direction of the maximum macro-seismic effect, area of intensity zones, distance, and azimuth to the extreme point where the earthquake was felt. The earthquake parameters were calculated using the attenuation formula of the macroseismic field with coefficients obtained by the R.Z. Burtiev for intermediate earthquakes of the Vrancea zone of the Carpathian region, separately in four azimuthal ranges. For crustal earthquakes, the general Blake-Shebalin macroseismic field equation was used. Despite possible errors associated with a correct assessment of intensity at observation points, as well as the accuracy of the coefficients of the macro-seismic field equation used for specific seismic events, it was possible to determine the type of each historical earthquake and obtain more accurate values of their parameters. The re-fined parameters of historical earthquakes will allow making a more holistic picture of the seismic hazard in the Carpathian region.

A Reappraisal of the 1968 Valle Del Belice Seismic Sequence (Western Sicily): A case study of Intensity Assessment with Cumulated Damage Effects

In 1968, six earthquakes with magnitude between 5.1 and 6.4 destroyed or heavily damaged several towns in the Valle del Belice (western Sicily), causing some three hundred fatalities. There have been some critical issues in the intensity assessment however in the macroseismic studies produced over the years , since the MCS scale was used as an estimation of shaking rather than a representation of the damage scenario; in practise, intensity was assigned for each earthquake of the sequence disregarding the effect of the cumulative damage. The case-study of the 2016-17 earthquakes in Central Italy reflected the difficulty in estimating the intensity in localities repeatedly hit by strong shocks, producing macroseismic parameters (epicentre, magnitude) inconsistent with the instrumental ones. As for the 1968 Valle del Belice sequence, the Parametric Catalogue of Italian Earthquakes CPTI15 reports the macroseismic parameters, owing to the inadequacy of the seismic network operating in Italy in that period. Aware of the issues related to epicentre locations and magnitudes calculated by the existing macroseismic datasets, here we propose a reappraisal of the 1968 earthquakes following a methodology tested during the 2016-17 seismic sequence in Central Italy. By a new analysis of the primary sources, we reconstruct the evolution of the damage scenario during the sequence and assess intensity by using the European Macroseismic Scale EMS-98; the new macroseismic parameters are finally compared with the ones of the CPTI15 catalogue. Lastly, we propose a procedure for minimizing the magnitude overestimation in case of seismic sequences, based on the computation of the total seismic moment M 0 .

The 2016–2017 earthquake sequence in Central Italy: macroseismic survey and damage scenario through the EMS-98 intensity assessment

In this paper we describe the macroseismic effects produced by the long and destructive seismic sequence that hit Central Italy from 24 August 2016 to January 2017. Starting from the procedure adopted in the complex field survey, we discuss the characteristics of the building stock and its classification in terms of EMS-98 as well as the issues associated with the intensity assessment due to the evolution of damage caused by multiple shocks. As a result, macroseismic intensity for about 300 localities has been determined; however, most of the intensities assessed for the earthquakes following the first strong shock on 24 August 2016, represent the cumulative effect of damage during the sequence. The earthquake parameters computed from the macroseismic datasets are compared with the instrumental determinations in order to highlight critical issues related to the assessment of macroseismic parameters of strong earthquakes during a seismic sequence. The results also provide indications on how location and magnitude computation can be strongly biased when dealing with historical seismic sequences.

Re-assessing the intensity values of Iranian earthquakes using EMS and ESI scales

Iran is a region with high seismicity but reliable seismometric networks were installed in this country only in the last decades. Hence, the analysis of macroseismic effects (seismic intensity) could be the only possible way for defining the parameters of most Iranian earthquakes. Various authors reported the intensity estimates of earthquakes in this region using different macroseismic scales. To apply modern methods of determining macroseismic parameters, intensity values need to be expressed in a uniform scale. In this study, we attempt such homogenization by considering all information we can find from the literature consisting of both descriptions of effects and intensity values to build a dataset of intensities for the Iran region as most complete as possible. We adopted the European Macroseismic Scale (EMS) as the reference scale as it is the most recent one and particularly detailed on building damage. We also considered the Environmental Seismic Intensity (ESI) scale in order to use information on environmental effects (ground deformation, landslides, liquefaction, etc.) that are poorly detailed by EMS. We compare our application of two scales based on a dataset of Iranian earthquakes for which we have descriptions of effects on both building (EMS) and environment (ESI), and found that, in about 80% of cases, assessed EMS and ESI intensities coincide one to other within one degree, that is the uncertainty which can be reasonably assumed for standard intensity estimates. In cases where we were not able to find the original descriptions of effects in literature and only intensity estimates reported in various scales, we convert these values by table of correspondence. In summary, we assessed intensities in a homogeneous scale for 512 Iranian earthquakes from 658 through 2013.

Fault parameters and macroseismic observations of the May 10, 1997 Ardekul-Ghaen earthquake

The Ardekul (Zirkuh) earthquake (May 10, 1997) is the largest recent earthquake that occurred in the Ardekul-Ghaen region of Eastern Iran. The greatest destruction was concentrated around Ardekul, Haji-Abad, Esfargh, Pishbar, Bashiran, Abiz-Qadim, and Fakhr-Abad (completely destroyed). The total surface fault rupture was about 125 km with the longest un-interrupted segment in the south of the region. The maximum horizontal and vertical displacements were reported in Korizan and Bohn-Abad with about 210 and 70 cm, respectively; moreover, other building damages and environmental effects were also reported for this earthquake. In this study, the intensity value XI on the European Macroseismic Scale (EMS) and Environmental Seismic Intensity (ESI) scale was selected for this earthquake according to the maximum effects on macroseismic data points affected by this earthquake. Then, according to its macroseismic data points of this earthquake and Boxer code, some macroseismic parameters including magnitude, location, source dimension, and orientation of this earthquake were also estimated at 7.3, 33.52° N–59.99° E, ~ 75 km long and ~ 21 km wide, and ~ 152°, respectively. As the estimated macroseismic parameters are consistent with the instrumental ones (Global Centroid Moment Tensor (GCMT) location and magnitude equal 33.58° N–60.02° E, and 7.2, respectively), this method and dataset are suggested not only for other instrumental earthquakes, but also for historical events.

Estimating the macroseismic parameters of earthquakes in eastern Iran

Macroseismic intensity values allow assessing the macroseismic parameters of earthquakes such as location, magnitude, and fault orientation. This information is particularly useful for historical earthquakes whose parameters were estimated with low accuracy.Eastern Iran (56°–62°E, 29.5°-35.5°N), which is characterized by several active faults, was selected for this study. Among all earthquakes occurred in this region, only 29 have some macroseismic information. Their intensity values were reported in various intensity scales. After collecting the descriptions, their intensity values were re-estimated in a uniform intensity scale. Thereafter, Boxer method was applied to estimate their corresponding macroseismic parameters.Boxer estimates of macroseismic parameters for instrumental earthquakes (after 1964) were found to be consistent with those published by Global Centroid Moment Tensor Catalog (GCMT). Therefore, this method was applied to estimate location, magnitude, source dimension, and orientation of these earthquakes with macroseismic description in the period 1066–2012. Macroseismic parameters seem to be more reliable than instrumental ones not only for historical earthquakes but also for instrumental earthquakes especially for the ones occurred before 1960. Therefore, as final results of this study we propose to use the macroseismically determined parameters in preparing a catalog for earthquakes before 1960.

Historical Seismicity of the Rijeka Region (Northwest External Dinarides, Croatia)—Part I: Earthquakes of 1750, 1838, and 1904 in the Bakar Epicentral Area

We present macroseismic analyses of three historical earthquakes that occurred in 1750, 1838, and 1904 in the Bakar epicentral area (Rijeka region, Croatia). Using various historical sources, we were able to compile intensity maps and assess macroseismic parameters for each of these events. The estimated epicenters lie close to known active fault systems, and the epicentral intensities are lower than those listed in catalogs. We have also identified a number of strong foreshocks and aftershocks which are currently missing from all catalogs. The three events analyzed, together with the Klana earthquake of 1870, are the largest known events to have occurred in these tectonically active parts of the northwest Dinarides. As such, they are important in characterizing seismic hazard in the vicinity of the main Croatian port, the city of Rijeka.

Construcción base de datos de escenarios de tsunami para el Pacífico colombiano

Los tsunamis son fenómenos naturales que aunque se presentan rara vez, afectan de forma evidente las zonas costeras, produciendo inundaciones, pérdida de vidas, modificaciones geomorfológicas del lecho marino y la costa, entre otras. El Pacífico colombiano hace parte del llamado “Cinturón de Fuego” dentro del cual se encuentran las poblaciones de Tumaco y Buenaventura, lugares donde se centrará el estudio. Para la determinación de los parámetros macrosísmicos de cada escenario propuesto se utilizaron las aproximaciones determinista y probabilista, y la simulación de los eventos de origen cercano, regional y lejano; se realizó mediante los modelos COMCOT (evento cercano y regional) y MOST (evento lejano). Igualmente, se obtuvo una base de datos con un total de 510 escenarios de tsunami, tanto para Tumaco como para Buenaventura, de los cuales es posible obtener información acerca del tiempo de llegada y la altura máxima del tren de olas de tsunami a la costa. Finalmente, se recomienda una ampliación de la base de datos, mediante una mayor densificación de escenarios de tsunami para el resto de poblaciones del Pacífico y Caribe colombiano.

The Algerian Homogenized Macroseismic Database (267–1989): A Deeper Insight into the Algerian Historical Seismicity

Online Material: Sources of information on earthquakes and earthquake list. Studying the effects of past earthquakes is an important component of predicting the effects of future earthquakes, and knowledge of historic earthquakes is important for understanding future earthquakes. The revision of the historical seismicity of Algeria started at the beginning of this century and is still going on (e.g., Harbi, Benouar, and Benhallou, 2003; Sebai and Bernard, 2008). The final objective of this reappraisal is to produce an earthquake catalog for Algeria that is as homogeneous as possible, compiled in a unique format, and covering a period of time going back as far as the existing data allow. The idea to make the macroseismic database accessible to the scientific community arose after the compilation and publication of the earthquake catalog of eastern Algeria (Harbi et al. , 2010), which became a starting point for a catalog dealing with the whole country. One of our objectives, when we performed that work, was to check the validity of the parameters reported in the earthquake catalog that we compiled from previous works, particularly for the damaging and destructive earthquakes. The only way to achieve this goal was to reexamine all the available seismological compilations (see the Materials for the Investigation of Algeria Seismicity section). We noticed that some authors (e.g., Roussel, 1973; Mezcua and Martinez, 1983) assigned an intensity value to the earthquakes without quoting their sources. This implies some uncertainty, particularly when the intensity is higher than VI, and suggests a damaging earthquake. Two important reasons led us to revise the macroseismic parameters of Algerian earthquakes, particularly the maximum intensity values, and to assess or reassess the intensities in terms of one single intensity scale, the European …

Linking ground motion measurements and macroseismic observations in France: a case study based on accelerometric and macroseismic databases

Comparison between accelerometric and macroseismic observations is made for three Mw = 4.5 earthquakes, which occurred in north-eastern France and south-western Germany in 2003 and 2004. Scalar and spectral instrumental parameters are processed from the accelerometric data recorded by nine accelerometric stations located between 29 and 180 km from the epicentres. Macroseismic data are based on French Internet reports. In addition to the single questionnaire intensity, analysis of the internal correlation between the encoded answers highlights four predominant fields of questions bearing different physical meanings: (1) “vibratory motions of small objects”, (2) “displacement and fall of objects”, (3) “acoustic noise” and (4) “personal feelings”. Best correlations between macroseismic and instrumental observations are obtained when the macroseismic parameters are averaged over 10-km-radius circles around each station. Macroseismic intensities predicted by published peak ground velocity (PGV)–intensity relationships agree with our observed intensities, contrary to those based on peak ground acceleration (PGA). Correlation between the macroseismic and instrumental data for intensities between II and V (EMS-98) is better for PGV than for PGA. Correlation with the response spectra exhibits clear frequency dependence for all macroseismic parameters. Horizontal and vertical components are significantly correlated with the macroseismic parameters between 1 and 10 Hz, a range corresponding to both natural frequencies of most buildings and high energy content in the seismic ground motion. Between 10 and 25 Hz, a clear lack of correlation between macroseismic and instrumental observations exists. It could be due to a combination of the decrease in the energy signal above 10 Hz, a high level of anthropogenic noise and an increase in variability in soil conditions. Above 25 Hz, the correlation coefficients between the acceleration response spectra and the macroseismic parameters are close to the PGA correlation level.

The 1992 Tafilalt seismic crisis (Anti-Atlas, Morocco)

The Tafilalt region, located at the eastern end of the Anti-Atlas chain in Morocco, was shaken on 23 and 30 October 1992 by two moderate earthquakes of magnitude mb ∼ 5 and intensity ∼ VI MSK64, which caused two deaths and great damage in the area between Erfoud and Rissani. The review of data available on the seismic crisis allowed us to improve the knowledge on the macroseismic, instrumental and source parameters of the earthquakes. The main results of the present study are: (1) location of the epicentres with the help of data from a close portable network allowed us to propose new epicentral coordinates at 31.361° N, 4.182° W (23 October) and 31.286° N, 4.347° W (30 October); both events have focal depths of 2 km; (2) the shock of 30 October was followed by a series of 305 aftershocks, most of which were located west of Rissani; the 61 best-constrained events had focal depths of 5 to 19 km and magnitudes 0.7 to 3; (3) the largest damage was located in an area between the two epicentres within the Tafilalt valley and was probably amplified by site effects due to the proximity of the water table within the Quaternary sediments; (4) focal mechanisms of the main events correspond to strike-slip faulting with fault planes oriented N–S (left lateral) and E–W (right lateral); the only mechanism available for the aftershocks also corresponds to strike-slip faulting; (5) spectral analysis shows that the scalar seismic moment (Mo) of the first event is slightly larger than the second; the corresponding values of Mw are 5.1 and 5.0, respectively; (6) the dimensions of the faults for a circular fault model are 7.7 ± 1.4 and 7.4 ± 1.2 km, respectively; the average displacement is 4 cm for the first event and 3.7 cm for the second; the stress drop is 0.4 and 0.3 MPa, respectively, in agreement with standard values; (7) the Coulomb Stress test performed for both earthquakes suggests a relationship between both events only when the used location is at the limit of the horizontal uncertainty; (8) finally, the occurrence of these shocks suggests that the Anti-Atlas is undergoing tectonic deformation in addition to thermal uplift as suggested by recent publications.

Macroseismic descriptions and parameters of Kamchatka earthquakes that occurred during the preinstrumental period of observation

This paper presents an analysis of the newly acquired macroseismic descriptions of several Kamchatka earthquakes that occurred in the 18th–19th centuries. The available data for two large earthquakes that occurred in 1737 were analyzed to show that even the very numerous descriptions of the October 17, 1737 earthquake are inadequate to determine the basic parameters (epicentral coordinates, magnitude, and epicentral intensity of shaking). The only sources of information on seismic events in Kamchatka for the 18th–19th centuries were reports of explorers, but their presence in the region was episodic and irregular. We therefore believe that the M=5–8.4 earthquakes were much more numerous during this period than indicated in all the published catalogs.