Article

Microtremor analysis of the Basilica of the Holy Sepulchre, Jerusalem

Authors:
  • Città Metropolitana di Firenze
  • Università di Firenze, Italy
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Abstract

Earthquakes along the Dead Sea Transform (DST) and in the Dead Sea Basin pose a considerable seismic hazard to the city of Jerusalem. To assess possible local site amplification due to either stratigraphical or morphological effects, we conducted seismic noise measurements at the Basilica of the Holy Sepulchre.The fact that the Basilica is built partially on detrital covers and alluvial filling provides further motivation for the study. Noise data are complemented by two earthquakes that were recorded at three seismic stations during the field measurement period.The results do not indicate site amplification at the Basilica ground, at least not for the major eigenfrequencies of the building.

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... With a growing interest in the protection of historical monuments, the usage of a quick and non-invasive microtremor HVSR methodology with no environmental impacts started to become more and more popular (e.g. Del Monaco et al. 2013;Ditommaso et al. 2010;Fäcke et al. 2006;Fiaschi et al. 2012;Gentile and Saisi 2007;Moisidi et al. 2004;Nakamura et al. 1999Nakamura et al. , 2000Stanko et al. 2016). It is the easiest and cheapest way to understand structural behaviour without doing any harm to a structure. ...
... The application of a microtremor HVSR methodology has been used to determine the natural frequency of historical monuments (e.g. Del Monaco et al. 2013;Ditommaso et al. 2010;Fäcke et al. 2006;Fiaschi et al. 2012;Gentile and Saisi Environ Earth Sci (2017) 2007; Moisidi et al. 2004;Nakamura et al. 1999, Stanko et al. 2016. Microtremor ambient noise measurements have been taken to detect potential weak points in the structure of Trakošćan Castle, primarily the construction of the Castle Tower due to earthquake damage and improper reconstruction (Stanko et al. 2016). ...
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This paper presents a major extension of seismic vulnerability research project on the site of Trakošćan Castle based on the initial horizontal-to-vertical-spectral-ratio (HVSR) results from Stanko et al. (2016). The estimated HVSR site frequencies and HV amplification at Trakošćan Castle can only be used as an indication of the initial soil site frequency and amplification, so-called natural soil model, corresponding to the subsoil profile without the influence of an earthquake. The equivalent-linear (EQL) site response analysis has been carried out for different earthquake scenarios for a maximum input rock peak ground acceleration (PGAROCK) that corresponds to return periods of 95 (0.08 g), 475 (0.18 g) and 1000 years (0.31 g). The aim of the research is to evaluate structural seismic design responses and to determine type and degree of damage caused by local site effect, which is the result of an alluvial basin and topographic influences. The main objective of this research is the formation of local microseismic zones based on an EQL analysis: surface spectral acceleration and amplification maps at the predominant frequency. Based on the HVSR frequency response of the core structure of Trakošćan Castle and the Tower itself (fundamental and higher frequency modes), maps of surface spectral acceleration and soil amplification at different frequencies (3, 5 and 10 Hz) are developed for different input PGAROCK levels (0.08, 0.18 and 0.31 g) to evaluate seismic response of the Castle. Observed amplifications are correlated with ground motion polarization and directionality of the ground motion from the alluvial basin to the hilltop. Shortening of predominant frequencies (lengthening of the period), particularly in the alluvial basin, has been observed with higher input PGAROCK in the EQL analysis. This effect is not manifested in the Trakošćan hill, and predominant frequencies match HVSR frequencies. The use of certain geophysical survey methods at historical sites is a big problem, because terrain features (e.g. steep hills, mountains, ridges, slopes, cliffs) create lack of space and make it impossible to carry out geophysical investigation. Microtremor measurements at historical sites can overcome this limitation and provide local seismic response and vulnerability behaviour of historical monuments without destroying their authenticity. Also, computational modelling can greatly improve the results. The EQL site response analysis on the site of Trakošćan Castle has confirmed and improved the results of seismic response and vulnerability based on HVSR method.
... Therefore, the main aim of this study is two-fold: (a) the assessment of earthquake damage in the Castle after the earthquakes that occurred in 2020, and (b) the comparison of pre-(2016) and post-earthquake (2021) ambient vibration measurements of critical points. Pre-and post-earthquake ambient vibration measurements in historical buildings can help to identify potential hidden cracks in thick walls and to detect potential weak points in the complex structure [9,10]. Changes in the fundamental frequencies can provide a useful tool for vulnerability diagnosis [11,12]. ...
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Trakošćan Castle, built on a rocky peak in the late 13th century, is a cultural heritage site protected as a historical entity by the Republic of Croatia. The Castle is constructed as a highly irregular masonry structure with timber or shallow masonry arches, vaults or dome floors. It was substantially renewed, upgraded and partially retrofitted from the 16th century until the year 2000. The M5.5 (VIII EMS) and M6.2 (VIII-IX EMS) earthquakes, which struck the city of Zagreb on 22 March 2020 and the Pokupsko-Petrinja area on 29 December 2020, strongly shook the Castle’s structure. Earthquake damage was observed and assessed by visual inspection accompanied by ambient vibration measurements. The slight cracks that appeared on masonry arches were found to be critically positioned, and can likely lead to the arches’ collapse if their spreading is not prevented. Ambient vibration measurements, which were compared to pre-earthquake ones, revealed the decrease in the fundamental frequencies of the Castle’s central tower unit and the second floor, thus possibly indicating the loss of structural stiffness as a consequence of the earthquake damage.
... In fact, these methods are normally employed both to test the conservation status of buildings/structures as their natural frequencies, and to assess damping and modal shapes, that are directly related to the structural rigidity and integrity. The bibliography about buildings/structures seismic risk/vulnerability assessment, as well as their seismic dynamic characterization, is wide (Stewart and Fenves 1998; Ramos et al. 2010, Fiaschi et al. 2012, Barbieri et al. 2013 Casolo et al. 2013; Russo 2013; Asteris et al. 2014; Ceravolo et al. 2014; Aguilar et al. 2015; Lacanna et al. 2016 and references within, and Pazzi et al. 2016a, b). On the other hand, papers about the seismic response of structures/buildings during conservation/safety works are missing, even thought the seismic vibration monitoring (SVM) is a technique widely used during these kind of works. ...
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Background The concepts of disaster risk reduction and disaster risk management involve the development, improvement, and application of policies, strategies, and practices to minimize disaster risks throughout society. Nowadays, preserving architectural heritage and ancient monuments from disasters is an important issue in the cultural life of modern societies. The “health” of a building/structure may be evaluate by its deterioration or damage level: monitor the aging and promptly detect relevant damages, play a central role, and structure dynamic characterization and microtremor analysis are considered powerful techniques in this field. A wide bibliography about structures/buildings seismic dynamic characterization is counterpoised to a missing one about their seismic response during conservation/safety works. This paper focus on the seismic response and monitoring of a historical masonry embankment wall during the conservation works carried out after a riverbank landslide that seriously damaged it. ResultsThe H/V results of the acquired traces show that main resonance frequency of the masonry embankment wall is between 4 Hz and 15 Hz, in agreement with the frequency range of roughly 10-meters-high, squat and monolithic structure. The whole monitoring period can be divided into three intervals corresponding to three different kind of workings: i) piling work; ii) parapet breakdown, excavation, embankment arrangement and foot wall consolidation; iii) backfill and restoring of the original condition, ordinary construction activities. The maximum peak component particle velocity substantial increase during the second period. All the stations have a higher energy content in the 10-20 Hz frequency range, but the spectra analysis clearly shows that the NS component, perpendicular to the wall, is the most stressed one. Moreover, despite the considerable distance from the August 24 Central Italy earthquake epicentre, the earthquake waveform is clearly recognizable at each station. In fact, the energy is focused around 2 Hz and the signals show directivity neither for the spectrum nor for the H/V. Conclusion This work may contribute to characterize the vibrations induced by piling work at close range, and help to define the maximum acceptable vibration pattern for such structures, since literature is missing of such case studies. The maximum peak component particle velocity values clearly showed the work advancement. This paper also shows how the H/V technique is a valuable method to estimate the resonant frequency not only of buildings, but also of a squat and monolithic structure like the Lungarno Torrigiani masonry embankment wall.
... Microtremor measurements in buildings and structures were used to assess the dynamic structural characteristics, fundamental frequencies of structures, and the possible soil-structure interaction/resonance (e.g., Gallipoli et al. 2010;Gosar 2012;Herak 2011). With the growing interest to protect historical monuments, the application of the quick and noninvasive microtremor HVSR methodology with no environmental impacts started to become more and more used (e.g., Fäcke et al. 2006;Fiaschi et al. 2012;Gentile and Saisi 2007;Moisidi et al. 2004;Nakamura et al. 1999Nakamura et al. , 2000. ...
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The Trakošćan Castle was built on the rocky peak of the hill in the thirteenth century. Castle structure has weakened with time, wars, inappropriate protection, and earthquakes. On 16 March 1982, the Tower Castle and part of second floor were damaged by an earthquake (ML= 4.5) with an epicenter 20 km distance from Mt. Ivančica. Afterwards, it was completely reconstructed. Today the cultural heritage of the Trakošćan Castle is protected as a historical entity by the Republic of Croatia. The Horizontal-to-Vertical-Spectral-Ratio (HVSR) method was applied for the purpose of local seismic response, protection from earthquake, structural seismic vulnerability of weak points, and structural restoration of the Trakošćan Castle related to the 1982 earthquake (microtremor measurements in free-field and in the Tower Castle). The free-field HVSR results (soil fundamental frequencies, amplification factors, shear wave velocity distribution, estimated bedrock depth, and directional effects on ground motion) are compared to the local geology, propagation path, and topographic effects to the estimated local seismic response. The dynamic behavior of the Tower Castle is demonstrated along different axes by the comparison of the directional HVSR analysis to the horizontal components (NS/V and EW/V) and the amplitude spectra (NS, EW and UD). The modal frequency response identifies weak points of the Tower Castle structure. Based on the HVSR analysis, the damage at Trakošćan site, related to the 1982 earthquake, occurred due to the local geology and topographic effects (seismic energy directed through the alluvial basin and trapped into the hill) and the improper way of the Tower Castle construction in the past and the reconstruction after the earthquake.
... The methodical study of seismic safeguard of artistic heritage has considerably spread in the last years, thus increasing researchers' interest in problems concerning monumental buildings. In particular, the seismic safety of art objects, that are the objects generally contained within Museums, is a research field of great interest, being part of research and policy in the more general field of Cultural Heritage, with contribution of several local government and European research grants (Liberatore 2000;Fiaschi et al. 2012). It must be noted, in fact, that buildings of historical and cultural significance may contain objects of inestimable value, for which there is no assessment of their effective vulnerability related to how they are displayed or stored. ...
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The problem of reducing the seismic risk for art objects, that are the objects generally contained within Museums, is of great interest. The first studies were performed in Japan and were successively organized in a general framework by a research program performed at Southern California University and sponsored by the Getty Museum at Malibu, California. In these papers and in the following Italian studies, the theoretical models for the problem concerning vases and statues are based on the dynamic behavior of rigid blocks and have been deeply developed. Unfortunately, because of the great lack of experimental data, determinant parameters for the problem characterization (like the friction between two superimposed blocks or between the art object and the support plane) are often assumed without reference to real values derived from laboratory tests. This paper presents the results of a research program containing the experimental determination of the friction coefficient between the art object and the support (by means of a testing apparatus on purpose realized) together with dynamic tests performed on simple-shaped objects made of different materials. The dynamic tests were performed using an unidirectional shaking table and different supporting surfaces, so that the influence of different friction coefficients has been analyzed.
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Ambient seismic noise measurements were conducted inside the Holweide Hospital (Cologne) for checking whether its frequencies of vibration fall into the range where soil amplification is expected. If this is the case, damage might increase in case of an earthquake due to an amplified structural response of the building. Two different techniques were used: the ratio between the horizontal and vertical components of the spectra recorded at stations located inside the building and the ratio between the corresponding components of the spectra recorded simultaneously inside the building and at a reference station placed outside. While the former method might be preferred because of less equipment involved, the latter has the advantage of producing more stable results and deleting automatically the influence of the sedimentary cover, which might obscure some eigenfrequencies of vibration of the building. An independently performed finite-element analysis of the hospital showed a good correlation between measured and calculated eigenmodes.
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This article is of an inter-disciplinary nature, relevant to the fields of both earth sciences and historiography, which come together in the investigation of long-term earthquake hazard. The paper emphasises the need for systematic and consistent analysis of historical earthquake data and sets out an example for such a task. The results from the historical study of earthquakes will be of value to earth scientists and engineers only when historical information is converted into “numbers” representing epicentral location and magnitude of the events, accompanied by an estimate of the reliability of their assessment. However, as we go further back in time before our era, the historical record gradually disappears and the archaeological record takes over. Unfortunately, the archaeological record is too coarse and ambiguous, without any precise internal archaeological indicators. Dating is based on, or influenced by the very few historical records, such as in the Bible and inscriptions, which provide an example of how their assumed accuracy may influence archaeologists' interpretation and dating. Quite often this develops into a circular process in which archaeological assumptions or theories are transformed into facts and used by earth scientists to confirm the dates and size of their proposed events. In this article we discuss the problems that arise when Biblical and archaeological information is used at face value to assess earthquakes in the Holy Land. This combination may produce earthquakes of hypothetical location and of grossly exaggerated magnitude with consequences for the assessment of seismic hazard.
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A high-resolution Holocene seismic history of the Dead Sea Transform (DST) is established from laminated sedimentary cores recovered at the shores of the Dead Sea. Radiocarbon dating and annual laminae counting yield excellent agreement between disturbed sedimentary structures (identified as seismites) and the historical earthquake record: All recent and historical strong events of the area were identified, including the major earthquakes of A.D. 1927, 1837, 1212, 1033, 749, and 31 B.C. The total of 53 seismites recognized along the entire Holocene profile indicate varying recurrence intervals of seismic activity between a few and 1000 years, with a conspicuous minimum rate at 2100–31 B.C. and a noticeable maximum during the past six to eight centuries. Most of the epicenters of the correlated earthquakes are situated very close to the Dead Sea (within 150 km) or up to 400 km north of it along the DST. Between 1000 B.C. and A.D. 1063, and from A.D. 1600 to recent time the epicenters are all located on the northern segment of the DST, whereas prior to 1000 B.C. and between A.D. 1000 and 1600 they appear to scatter along several segments of the DST. We establish how the local intensity exerts a control on the formation of seismites. At historically estimated intensities greater than VII, all well documented earthquakes are correlated, whereas at intensities smaller than VI none are matching.The periods with enhanced earthquake rate along the DST correlate with those along the North Anatolian Fault as opposed to the intervening East Anatolian Fault. This may indicate some elastic coupling on plate-boundary scale that may also underlie escape and extrusion tectonics, typical of continental collision.
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The citadel of Machupicchu is probably the most famous Inca heritage site in Peru. Considering the seismically active region, this research is an attempt to perform a seismic risk analysis of the heritage structures at Machupicchu. A systematic approach is adopted for this purpose. Characteristic seismicity of the region, where these historical constructions are located, is discussed based on the seismic hazard analysis. Evaluation of the vulnerability of the structures under the prevalent earthquake hazard is another important aspect essential for risk analysis. As a first step to proper understanding of the seismic behavior of these heritage structures, typical elements of Inca construction are studied by simple analytical models to verify basic aspects of structural integrity. The possibility that peak ground acceleration corresponding to even relatively low hazard may produce instability in some structural components like gable walls was noted. In view of this preliminary result, attempt was made to identify the dynamic characteristics of typical buildings units from more detailed investigation. This forms part of the outcome from the field study program, which included microtremor measurement of free field as well as typical constructions, planned and undertaken by the authors. The results of the microtremor measurements are utilized to estimate the dynamic characteristics of the Inca stone structures. That is, the analytical results are compared with the measurements to calibrate the analytical model. Since microtremor measurements involve very small displacements, the characteristics of stones structures thus obtained correspond to elastic behavior applicable to small strain condition. Based on this scheme, an approach has been proposed to evaluate the seismic behavior and hence the seismic vulnerability of these structures. The procedure also permits identification of the probable mode of failure of the structures concerned.
Some Comments on Seismicity in Israel, Performance Assessment & Damage to Historic Monuments in Jerusalem
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1 – Virtual exterior view of the Basilica of the Holy Sepulchre and adjacent buildings from the NE obtained by a 3D laser scanner survey (courtesy of
  • Fig
Fig. 1 – Virtual exterior view of the Basilica of the Holy Sepulchre and adjacent buildings from the NE obtained by a 3D laser scanner survey (courtesy of Prof. G. Tucci, Dipartimento di Costruzioni e Restauro, Università di Firenze).
Zones of required investigation for earthquake-related hazards in Jerusalem
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Salomon A, Katz O, Crouvi O. Zones of required investigation for earthquake-related hazards in Jerusalem, Nat Hazards, 2010;53:375-406.