Macroseismic field of the October 27, 2004 Vrancea (Romania) moderate subcrustal earthquake

On October 27, 2004, a moderate size earthquake occurred in the Vrancea seismogenic region (Romania). The Vrancea seismic zone is an area of concentrated seismicity at intermediate depths beneath the bending area of the southeastern Carpathians. The 2004 M _w?=?6 Vrancea subcrustal earthquake is the largest seismic event recorded in Romania since the 1990 earthquakes. With a maximum macroseismic intensity of VII Medvedev–Sponheuer–Kárník (MSK-64) scale, the seismic event was felt to a distance of 600 km from the epicentre. This earthquake caused no serious damage and human injuries. The main purpose of this paper is to present the macroseismic map of the earthquake based on the MSK-64 intensity scale. After the evaluation of the macroseismic effects of this earthquake, an intensity dataset has been obtained for 475 sites in the Romanian territory. Also, the maximum horizontal accelerations recorded in the area by the K2 network are compared to the intensity values.     

Transfrontier macroseismic observations of the Ml = 5.4 earthquake of February 22, 2003 at Rambervillers,France

The 2003 Ml = 5.4 Rambervillers earthquake, north-east of France, is the largest seismic event recorded north of the Alps since the 1992 Ms = 5.3, I₀ = VII, Roermond earthquake, Netherlands. With a maximum macroseismic intensity of VI-VII EMS-98, the 2003 event was broadly felt to a distance of 300 km from the epicentre. It provides a unique opportunity to test and compare the different procedures used in France, Germany and Switzerland when evaluating macroseismic intensities. The main purpose of this paper is to present a common transfrontier macroseismic map based on the EMS-98 intensity scale. Maximum horizontal accelerations recorded in the area are compared to the intensity values, and we propose to use a differential technique to re-estimate the magnitude of the 1682 Remiremont, I₀ = VIII, earthquake, which occurred 40 km south of Rambervillers.     

The earthquake of Carnuntum in the fourth century a.d. – archaeological results, seismologic scenario and seismotectonic implications for the Vienna Basin fault, Austria

Excavations in the former Roman provincial capital of Pannonia Superior, Carnuntum, 40 km east of Vienna revealed damaged masonry structures from many parts of the ancient settlements. A compilation of structurally damaged buildings has formerly been given by Kandler (Acta Archaeol Acad Sci Hung, 41:313–336, 1989), who related damage to an earthquake in the middle of the fourth century a.d. This paper reviews and supplements these data, and discusses the significance of the style of damage. It is concluded that seismic damage is the only likely interpretation for the damaging mechanism. Although archaeological age dating for the individual collapsed buildings only constrains the timing of their destruction to a few decades around 350 a.d., we assume a single damaging event. In spite of the restrictions on damage assessment by the nature of the archaeological data, it is possible to give a reasonable appraisal of macroseismic intensity. The tentative seismological interpretation of damage leads to an intensity estimate of about nine of the European macroseismic scale (EMS-1998). Comparison with macroseismic data of modern earthquakes in the region, which show a rapid decrease of intensity with distance form the epicentre, indicate a near-by seismic source unless exceptionally high epicentral intensities are assumed for the fourth century event. The most likely source is an active sinistral strike-slip fault (Lassee Fault) passing about 8 km NW of the archaeological site. The fault belongs to Vienna Basin fault system with about 2 mm sinistral movement per year. The system is characterized by fault segmentation and distinct seismicity along the different segments. Moderate seismicity during the last centuries at the southern segments (e.g., Schwadorf 1927, I ₀=8) strongly contrasts from the Lassee fault segment with Carnuntum as the only known severe earthquake. The earthquake of Carnuntum provides evidence for the overall seismic style of deformation along this segment, which previously has not been regarded seismically active. Also, the fourth century earthquake is the strongest event known from the Vienna Basin fault so far.     

The Mercalli family of seismic intensity scales

Measurement theory is applied to the seismic intensity scales for the purpose of classifying them. Some basic tenets of scale classification are discussed, along with properties of scales of different ranks. The seismic scale is tested for uniformity. It is shown that the Mercalli-type seismic intensity scales at present in use have the rank of an interval scale, thus proving that arithmetic operations can be applied to macroseismic estimates expressed in the standard intensity grades.     

Revising macroseismic data in Switzerland: The December 20, 1720 earthquake in the region of Lake Constance

Upgrading the Earthquake Catalog of Switzerland (ECOS) included revising the earthquake of 1720. This change has major importance for history and seismology.Although that quake has been the subject of several publications, none was based on critical methods. This re-evaluation of the event is built upon a new and more reliable database established after investigating archives and libraries. Using data from such historical sources, we assigned new site intensities, adopting the criteria established by the European macroseismic scale EMS 98 (Grünthal, 1998).We discovered that the event had been assigned an overestimated intensity, due to interpretation errors in former earthquake catalogs and compilations. We recommend reducing the intensity from I₀= VIII to I₀= VI (EMS 98). The moment magnitude is given as M_W= 4.6. Since the event had been considered the largest for its respective area, downgrading it now will influence the seismic hazard assessment for this region.     

An ordered probit model for seismic intensity data

Seismic intensity, measured through the Mercalli–Cancani–Sieberg (MCS) scale, provides an assessment of ground shaking level deduced from building damages, any natural environment changes and from any observed effects or feelings. Generally, moving away from the earthquake epicentre, the effects are lower but intensities may vary in space, as there could be areas that amplify or reduce the shaking depending on the earthquake source geometry, geological features and local factors. Currently, the Istituto Nazionale di Geofisica e Vulcanologia analyzes, for each seismic event, intensity data collected through the online macroseismic questionnaire available at the web-page www.haisentitoilterremoto.it. Questionnaire responses are aggregated at the municipality level and analyzed to obtain an intensity defined on an ordinal categorical scale. The main aim of this work is to model macroseismic attenuation and obtain an intensity prediction equation which describes the decay of macroseismic intensity as a function of the magnitude and distance from the hypocentre. To do this we employ an ordered probit model, assuming that the intensity response variable is related through the link probit function to some predictors. Differently from what it is commonly done in the macroseismic literature, this approach takes properly into account the qualitative and ordinal nature of the macroseismic intensity as defined on the MCS scale. Using Markov chain Monte Carlo methods, we estimate the posterior probability of the intensity at each site. Moreover, by comparing observed and estimated intensities we are able to detect anomalous areas in terms of residuals. This kind of information can be useful for a better assessment of seismic risk and for promoting effective policies to reduce major damages.     

Macroseismic foundations of seismic microzoning

The Russian seismic safety regulations are based on macroseismic evaluations in terms of seismic intensity values. According to the seismic scale, intensity value determines both the degree of destruction of buildings and engineering structures and such parameters of seismic impacts as peak ground accelerations and response spectra. Application of macroseismic approach in various aspects of seismic microzoning has led to achievements in earthquake engineering; these aspects are discussed. The advantages and disadvantages of the macroseismic approach are considered.     

The 7 and 11 May 1984 earthquakes in Abruzzo-Latium (Central Italy): reappraisal of the existing macroseismic datasets according to the EMS98

The aim of this paper is to provide a complete and reliable macroseismic knowledge of the events that stroke a large area in Central Italy on 7 and 11 May 1984. Previous studies, together with original accounts integrated with new and unpublished information, have been gathered and examined in order to re-evaluate macroseismic intensities in terms of the European Macroseismic Scale (EMS98). New intensity maps have been compiled; the total number of localities with available information for both the shocks increases from 1254 of the previous study to 1576. On the basis of the new dataset, the macroseismic magnitude of the first shock is M_W 5.6 which is lower than the previous macroseismic computation (M_W 5.7). Moreover, the topic of assessing macroseismic intensity in the presence of multiple shocks has been also investigated, proposing an unconventional approach to presenting the macroseismic data: an overall picture of the cumulative effects produced by all the seismic sequence is given to support a partial but faithful reconstruction of the second shock. This approach is inspired by the common experience in interpreting historical seismic sequences and gives a picture of the impact of the 1984 events on the territory.     

23 November 1980 Irpinia–Basilicata earthquake (Southern Italy): towards a full knowledge of the seismic effects

This paper overviews the procedures and tools used for a systematic study of the macroseismic consequences caused by a strong earthquake that struck Southern Italy. The event referred to the 23 November 1980 (Io = X MCS, Ms = 6.9) which affected the Campania and Basilicata regions. Two aspects are addressed here: to broaden the knowledge of the macroseismic field and delineate damage maps of the sites affected on an urban scale. The target area of this study is the Basilicata region about which the current macroseismic information is poor. This research study, based only on unpublished documentary sources, supplies about 50 new assessments and about 30 new re-assessments of the macroseismic site intensity (MCS scale) as outputs. Moreover, about 80 thematic maps showing the damage pattern of the sites affected are also supplied. It is the first time that a large earthquake has been the subject of such extensive studies from a macroseismic point of view, with special attention to the analysis of damage effects at town scale.     

Further information on the macroseismic field in the Balkan area

Papazachos and Papaioannou (1997) (called PP97 hereinafter) studied the macroseismic field in the Balkan area (Greece, Albania, former Yugoslavia, Bulgaria and western Turkey) with the purpose of deriving attenuation and scaling relations useful for seismic hazard assessment and study of historical earthquakes. In his comment, Trifunac suggests that our analysis might exhibit certain bias for all countries except Greece due to problems mainly associated with the database (completeness, etc.), conversion of local intensity scales used in the Balkan countries, as well as to the local variations of the attenuation relation due to the variation of the geotectonic environment in this area. Specifically, his most important comments can be summarized as follows: a) The large participation of Greek data probably biased the scaling relations proposed in the study. b) The conversion relations used between local macroseismic scales are less accurate than their proposed such relations. c) The variation of attenuation (geometrical and anelastic) in different regions of the study area is important and local relations (instead of the proposed single relation) should be determined for seismic hazard assessment. In the following, we study in detail each of these possible bias sources. Additional work on the macroseismic field of the Balkan area shows that none of the previously described factors, suggested by Trifunac, introduces bias in the results presented by PP97. Specifically, it is shown that the database used by PP97 fulfills the basic requirements for a reliable determinations of attenuation and scaling relations proper for seismic hazard assessment in all five countries of this area. Evidence is presented that no strong geographical variation of the attenuation of macroseismic intensities of shallow earthquakes is observed. Relations between local version of intensity scales suggested by Shebalin et al. (1974) are shown to be reliable. Finally, it is demonstrated that national practices for estimation of macroseismic intensities may affect the results of seismic hazard assessment but proper formulation can be applied (PP97) which allows to take into account such differences in national practices. This formulation allows also to introduce and correct for anisotropic radiation at the seismic source as well as the incorporation of site effects.     

探讨地震宏观破坏场分布的影响因素

提出震后根据仪器定位的微观震中和断层构造的关系快速确定可能的宏观震中位置,并依此使用烈度经验分布模型来进行震害快速评估。这将提高直接用微观震中位置进行震害快速评估方法的精度。通过对全国133个主要地震的微观震中与宏观震中偏离量进行统计可知。偏离量在35km范围内的占88％,其余基本都在75km范围内。这样就给出了判定宏观震中的重点区域和分析区域。详细分析南北地震带66个震例及其与断层空间分布特征的关系。以及震源机制解结果后发现,影响宏观震中偏离的因素除仪器定位本身的误差外,主要还有断层展布方向、活动规模、断层相互交接特征及震级大小等。通过对这些影响因素的分类处理分析,建立了震后室内快速判定可能的宏观震中位置的原则和步骤。以该方法为基础,通过建立包含有关因素的全国断层数据库,即可在实际的震害快速评估中得以应用。     

Seismogenic deformations in the walls of the late medieval Yeni-Kale fortress in Eastern Crimea

The results of a macroseismic study of the late medieval Turkish Yeni-Kale fortress in Eastern Crimea are described. Despite the fact that the fortress’ structures were considerably affected by local landslide activity, military operations during the Crimean War, the Civil War, and the WWII, as well as by anthropogenic factors, such as railroads, etc., numerous specific deformations in the fortress walls suggest that the existing destruction and damage might be explained by strong seismic impacts. The local intensity of seismic oscillations could be I = (VIII)–IX points according to the MSK-64 macroseismic scale, and the direction of the combined maximum seismic impact could have a NW–SE strike. It is likely that the Turks abandoned the fortress without a battle because of its significant seismic damage and destruction in the 18th century, which had not yet been repaired by the time the Russian army arrived.     

On the Intensity Virtual Area Characterization in the Intensity Distribution Modelling by Macroseismic Planes

A procedure is proposed for the reconfiguration of the macroseismic planes relative to earthquakes that, being characterized by a reduced number of points of observed intensity due to a lack of information, or having the epicenter very close to the coastline, are characterized by an incomplete distribution of observed intensity levels. The design of a plurality of virtual areas, through which a distribution of intensity consistent with an anisotropic model of attenuation is depicted, allows a reliable determination of macroseismic parameters of the same seismic event.     

The 23 April 1909 Benavente earthquake (Portugal): macroseismic field revision

The 23 April 1909 earthquake, with epicentre near Benavente (Portugal), was the largest crustal earthquake in the Iberian Peninsula during the twentieth century (M _w = 6.0). Due to its importance, several studies were developed soon after its occurrence, in Portugal and in Spain. A perusal of the different studies on the macroseismic field of this earthquake showed some discrepancies, in particular on the abnormal patterns of the isoseismal curves in Spain. Besides, a complete list of intensity data points for the event is unavailable at present. Seismic moment, focal mechanism and other earthquake parameters obtained from the instrumental records have been recently reviewed and recalculated. Revision of the macroseismic field of this earthquake poses a unique opportunity to study macroseismic propagation and local effects in central Iberian Peninsula. For this reasons, a search to collect new macroseismic data for this earthquake has been carried out, and a re-evaluation of the whole set has been performed and it is presented here. Special attention is paid to the observed low attenuation of the macroseismic effects, heterogeneous propagation and the distortion introduced by local amplifications. Results of this study indicate, in general, an overestimation of the intensity degrees previously assigned to this earthquake in Spain; also it illustrates how difficult it is to assign an intensity degree to a large town, where local effects play an important role, and confirms the low attenuation of seismic propagation inside the Iberian Peninsula from west and southwest to east and northeast.     

The December 5th, 1456 Central Italy Earthquake: A Discussion of a Possible Reshaping of Intensity Distribution by Vectorial Modelling

--A study of the intensity distribution of the earthquake of December 5th 1456, which affected a large area of central and southern Italy was carried out, verifying, through a recently proposed methodology, the two hypotheses assumed by different authors for one single seismic event and three distinct and close ones. This methodology is based on a vectorial modelling of the macroseismic intensity distribution which aims at determining the epicentre and the principal (minimum and maximum) attenuation directions.¶The study was structured, considering each of the two assumed hypotheses, in a set of tests obtained for the macroseismic field and the intensity map, by analysing different configurations of the observed intensity distribution.¶The results obtained are in agreement with the hypothesis of the time coexistence of three distinct seismic events, for which the calculated epicentres and the principal attenuation directions are compatible with the observed intensity distribution and with the tectonic trend of the Apennine region, respectively.     

The August 27, 2008, <Emphasis Type="Italic">M</Emphasis><Subscript>W</Subscript> = 6.3, Kultuk earthquake effects in the Nearepicenter zone: Macroseismic survey results

In this work, the macroseismic effects of the Kultuk earthquake (M _W = 6.3), which took place on August 27, 2008 in the southwestern closure of the Baikal Lake, are under consideration. The intensity of shocks in inhabited localities located in the epicentral zone reached 7–8 points on the MSK-64 scale. The earthquake was named after the local settlement of Kultuk, which was the mostly damaged area by the earthquake. The considered seismic event caused significant material damage (about 250 million rubles according to preliminary estimates). In inhabited localities of Southern Pribaikalie thousands of cases of damaged ovens and chimneys were registered. Some buildings were highly damaged and, accordingly, they are unfit for further use. The earthquake was the cause of numerous rockslides, rockfalls, and landslides on steep natural and artificial slopes. A macroseismic survey allowed us to establish the asymmetrical distribution of the intensity of shocks relative to the epicenter.     

The October 4th, 1983 — Magnitude 4 earthquake in Phlegraean Fields: Macroseismic survey

On Oct. 4th, 1983 the area of Phlegraean Fields, near Naples (Southern Italy) was shaked by an earthquake of magnitude (M _L) 4.0 that caused some damage in the town of Pozzuoli and its surroundings. This seismic event was the largest one recorded during the recent (1982–84) inflation episode occurred in the Phlegraean volcanic area, and a detailed macroseismic reconstruction of the event was carried out.Failing macroseismic data on other earthquakes occurred in Phlegraean Fields, the attenuation law of the intensity as a function of the distance as obtained for the Oct. 4th earthquake was compared with those obtained for other volcanic areas in central Italy —i.e., Tolfa, Monte Amiata — in order to check the reliability of the results obtained for Phlegraean Fields.The Blake's model of the earthquake of Oct. 4th, 1983 does not agree with the experimental data because isoseismals contain areas larger than those shown by the model. This result has been interpreted as an effect of energy focusing due to a reflecting layer 6–8 km deep.     

On the vulnerability assessment of monumental buildings

In all European countries the will to conserve the building heritage is very strong. Unfortunately, large areas in Europe are characterised by a high level of seismic hazard and the vulnerability of ancient masonry structures is often relevant. The large number of monumental buildings in urban areas requires facing the problem with a methodology that can be applied at territorial scale, with simplified models which need little easily obtainable, data. Within the Risk-UE project, a new methodology has been stated for the seismic vulnerability assessment of monumental buildings, which considers two different approaches: a macroseismic model, to be used with macroseismic intensity hazard maps, and a mechanical based model, to be applied when the hazard is provided in terms of peak ground accelerations and spectral values. Both models can be used with data of different reliability and depth. This paper illustrates the theoretical basis and defines the parameters of the two models. An application to an important church is presented.     

Assessing the intensity of the September 17, 2003, Khoito-Gol earthquake from instrumental and macroseismic data

The present study is devoted to the assessment of shaking intensities due to the September 17, 2003, earthquake occurring in the Khoito-Gol basin (southwestern flank of the Baikal Rift System). The instrumental and macroseismic data used here were acquired during an investigation into the impact of this seismic event. The highest intensity of shaking, VI, was recorded at Khoito-Gol, the human settlement that was the nearest to the instrumental epicenter. A nonuniform distribution of intensity was found for different directions from the epicenter. A scatter of as much as two intensity units was recorded at one settlement.