15 research outputs found

    Strong ground motion from the seismic swarms preceding the 2021 and 2022 volcanic eruptions at Fagradalsfjall, Iceland

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    The Geldingadalir and Meradalir eruptions at Mt. Fagradalsfjall in the Reykjanes Peninsula on 19 March 2021 and 3 August 2022, respectively, were preceded by intense volcano-tectonic swarms. Eight earthquakes with M ≥ 5 were recorded by the Icelandic Strong Motion Network. We present an overview of the seismicity in Fagradalsfjall, and salient features of the strong ground motion caused by the swarms in the epicentral area. The largest recorded horizontal Peak Ground Acceleration (PGA) was ~ 0.45 g at Grindavík, which is the strongest PGA recorded in Iceland since the MW6.3 2008 Ölfus Earthquake. Recorded waveforms show a rich long-period energy content, with a burst of higher frequencies at the beginning of shaking. This leads to larger response spectral accelerations at long periods that those from typical shallow crustal earthquakes. Moreover, an empirical mixed-effects ground motion model for PGA, PGV and PSA was calibrated for rock sites based on the available recordings. The attenuation rate from this model is similar to that introduced by Lanzano and Luzi (Bull Earthq Eng 18(1):57–76, 2020) which is based on data from volcanic events in Italy, but the magnitude scaling of our model is much lower. The overall results indicate that scaling and attenuation of ground motion from volcanic events and purely tectonic earthquakes in Iceland are different. This is an important observation because seismic hazard in parts of the Reykjavik area and of the central highlands, where important hydroelectric power plants are located, could potentially be dominated by events of volcanic origin. Therefore, it is important to take these observations into account for seismic hazard and risk assessment in Iceland

    Empirical seismic vulnerability assessment of Icelandic buildings affected by the 2000 sequence of earthquakes

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    Publisher's version (útgefin grein)In June 2000, two Mw6.5 earthquakes occurred within a 4-day interval in the largest agricultural region of Iceland causing substantial damage and no loss of life. The distance between the earthquake epicentres and the fault rupture was approximately 15 km. Nearly 5000 low-rise residential buildings were affected, some of which were located between the faults and exposed to strong ground motion from both events. The post-earthquakes damage and repair costs for every residential building in the epicentral region were assessed for insurance purposes. The database is detailed and complete for the whole region and represents one of the best quality post-earthquake vulnerability datasets used for seismic loss estimation. Nonetheless, the construction of vulnerability curves from this database is hampered by the fact that the loss values represent the cumulative damage from two sequential earthquakes in some areas, and single earthquakes in others. A novel methodology based on beta regression is proposed here in order to define the geographical limits on areas where buildings sustained cumulative damage and predict the seismic losses for future sequence of events in each area. The results show that the average building loss in areas affected by a single event is below 10% of the building replacement value, whilst this increases to an average of 25% in areas affected by the two earthquakes. The proposed methodology can be used to empirically assess the vulnerability in other areas which experienced sequence of events such as Emilia-Romagna (Italy) in 2012.The authors wish to offer their thanks to the Icelandic Catastrophe Insurance for placing the earthquake loss database and other relevant information at their disposal, and University of Iceland for a research Grant. Ioanna Ioannou and Tiziana Rossetto’s contribution to this study was Funded by the HORIZON2020 Project ‘IMPROVER’ (Grant Number: 653390). Ioannis Kosmidis was supported by The Alan Turing Institute under the EPSRC grant EP/N510129/1 (Turing award number TU/B/000082).Peer Reviewe

    Empirical vulnerability assessment for low rise RC, Timber and Masonry Icelandic buildings

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    The South Iceland Seismic Zone (SISZ) is about a 70-km long belt lying in the east-west direction and 10-15 km wide in the north-south direction. Approximately 20 earthquakes with magnitudes in the range of 6 to 7 have occurred in this zone since 1700. These events tend to occur in sequences and therefore structures may be exposed to strong ground motion from more than one event within a few days. The SISZ crosses the largest agricultural region in Iceland with small towns, farms and all the infrastructure assets of a modern society. On 17 and 21 of June, 2000, two Mw6.5 earthquakes struck the SISZ. Both were shallow strike-slip quakes with parallel fault ruptures and with an approximately 16 km fault-to-fault distance. They affected nearly 5000 lowrise residential buildings. All buildings in Iceland are registered in a detailed official inventory. Furthermore, all buildings are covered by compulsory catastrophic insurance and therefore, after the earthquakes, damage and repair costs for every damaged building were assessed for insurance purposes. The collected loss data merged with the real estate register data were used in the present study to assess a vulnerability model based on beta regression.Critical in the development of the methodology were the determination of which buildings sustained damage due to one or two events, secondly the problem of substantial variability in the loss data, and finally uneven spatial distribution of the buildings due to villages on one hand and single farms on the other hand

    Tool for analysis of multichannel analysis of surface waves (MASW) field data and evaluation of shear wave velocity profiles of soils

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    Multichannel analysis of surface waves (MASW) is a fast, low-cost, and environmentally friendly technique to estimate shear wave velocity profiles of soil sites. This paper introduces a new open-source software, MASWaves, for processing and analysing multichannel surface wave records using the MASW method. The software consists of two main parts: a dispersion analysis tool (MASWaves Dispersion) and an inversion analysis tool (MASWaves Inversion). The performance of the dispersion analysis tool is validated by comparison with results obtained by the Geopsy software package. Verification of the inversion analysis tool is carried out by comparison with results obtained by the software WinSASW and theoretical dispersion curves presented in the literature. Results of MASW field tests conducted at three sites in south Iceland are presented to demonstrate the performance and robustness of the new software. The soils at the three test sites ranged from loose sand to cemented silty sand. In addition, at one site, the results of existing spectral analysis of surface waves (SASW) measurements were compared with the results obtained by MASWaves.The project has been supported financially by grants from the University of Iceland Research Fund, the Icelandic Road and Coastal Administration, and the Energy Research Fund of the National Power Company of Iceland.Peer Reviewe

    What scientific information on the seismic risk to non-structural elements do people need to know? Part 1: Compiling an inventory on damage to non-structural elements

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    Understanding damage  to  non-structural  elements,  identifying sources  of  critical issues,  and  how  damage  affects  the  functionality of facilities are all critical aspects for developing general recommendations concerning disaster risk management. In the present paper a review of non-structural damage caused by recent earthquakes was performed in several localities exposed to seismic hazard such as Mt. Etna in Italy, Lisbon and Azores islands in Portugal and southern Lowland in Iceland. This was needed in order to derive the most common non-structural damage framed into the local situation, which in turn is a basic requirement for a well tailored communication campaign. The observed damage to non-structural elements as derived in this study led to the conclusion that the most commonly damaged elements are partition walls, ceiling systems, non-structural vaults, chimneys, building contents and storage racks. Analyses proved that substantive efforts are needed worldwide to improve techniques for reducing damage to non-structural elements. Non-structural mitigation represents a major opportunity for immediate low-cost action to reduce the impacts of earthquakes at home, school and workplaces. Research results within the KnowRISK EU project was the reference ground upon which a wide range of tools for multi-stakeholders (students, business and citizens) to improve seismic performance of non-structural elements and reducing the associated economic losses, loss of functionality, and potential threats to life safety was designed

    Vibrations measurement of the funicular generated vibrations on Gediminas Hill north part slope

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    An experimental measurements of the funicular generated vibrations provided after Gediminas Hill North part slope landslide, which occurred on 2016. The geology of Gediminas Hill made up strata of Quaternary system late Pleistocene glacial and glaciofliuvial coarse and fine deposit.The purpose of this measurement was to determine, whether funicular generated vibrations during exploitation is the significant slope destabilizing factor. For vibration measurements in X, Y and Z directions were implemented equipment, developed by the authors. Measurements in 25 different points on the Gediminas Hill slope were perfirmed during funicular movement up and down. Analysis of obtained results revealed, that the highest vibration level mainly localized at the top of funicular foundations, wave energy is not large, propagating waves greatly dampens in the soil and there is no effect for general slope stability and the funicular exploitation was not the main reason of the occurred landslide in 2016 Spring
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