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A comprehensive catalogue of historical earthquakes, with accurate epicentres and harmonised magnitudes is a crucial resource for seismic hazard mapping. Here we update and combine catalogues from several sources to compile a catalogue of earthquakes in and near Iceland, in the years 1900–2019. In particular the epicentres are based on local information, whereas the magnitudes are based on teleseismic observations, primarily from international online catalogues. The most reliable epicentre information comes from the catalogue of the Icelandic Meteorological Office, but this is complemented with information from several technical reports, scientific publications, and newspaper articles. The catalogue contains 1281 moment magnitude (Mw) ≥4 events, and the estimated completeness magnitude is Mw 5.5 in the first years, going down to Mw 4.5 for recent years. The largest magnitude is Mw 7.0. Such merging of local data and teleseismic catalogues has not been done before for Icelandic earthquakes, and the result is an earthquake map with much more accurate locations than earlier maps. The catalogue also lists 5640 additional earthquakes on the Mid-Atlantic Ridge, north of 43∘, with both epicentres and magnitudes determined teleseismically. When moment magnitudes are not available, proxy Mw values are computed using χ2 regression, normally on the surface-wave magnitude but exceptionally on the body-wave magnitude. Magnitudes of Mw≥4.5 have associated uncertainty estimates. The actual combined seismic moment released in the Icelandic earthquakes is found to be consistent with the moment estimated using a simple plate motion model, indicating that the seismic activity of the catalogue period might be typical of any 120-year time span. The catalogue is named ICEL-NMAR, and it is available online at http://data.mendeley.com (last access: 19 July 2021).

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).

Publisher's version (útgefin grein), Multichannel analysis of surface waves (MASW) is a seismic exploration method for determination of near-surface shear wave velocity profiles based on analysis of horizontally travelling Rayleigh waves. This paper aims to propose a methodology and recommendations for combining dispersion data from several multichannel records. The dispersion curves are added up within logarithmically spaced wavelength intervals and the uncertainty of the mean phase velocity estimates is evaluated by using classical statistics and the bootstrap. The results indicate that combining multiple dispersion curves, which have been gathered by receiver spreads of different lengths (but with the same midpoint), can increase the investigation depth of the survey, improve its resolution at shallow depth and overall improve the reliability of the results as compared to the use of a single record. Moreover, the uncertainty of the combined mean dispersion curve can be determined and further used to present the shear wave velocity profile with upper and lower boundaries., This work was supported by the University of Iceland Research Fund [Grant no. 73077]; the Icelandic Road and Coastal Administration [Grant no. 1800-373]; and the Energy Research Fund of the National Power Company of Iceland [Grant no. NYR-18-2017].

Since 1983, 15 Icelandic bridges have been base isolated for seismic protection. Lead-rubber bearings have been used in all cases. Nine of these bridges are located in the South Iceland Lowland, which is an active seismic zone where earthquakes of magnitude seven can be expected. In June 2000 two Mw6.5 earthquakes struck in the area and in May 2008 a Mw6.3 event hit the area again. Four of the base isolated bridges were located in the near-fault area of these earthquakes with a fault-to-site distance of less than 15 km, and most likely three of them were subjected to strong low-frequency near-fault velocity pulses. None of the bridges collapsed or were severely damaged and all of them were open for traffic immediately after these events. Post-earthquake response analysis has indicated that the base isolation was important for the performance of the bridges.

Multichannel Analysis of Surface Waves (MASW) is a seismic exploration method to evaluate shear wave velocity profiles of near-surface materials. MASW was applied at seven locations in or close to the South Iceland Seismic Zone, providing shear wave velocity profiles for the top-most 15–25 m. The profiles were utilized for seismic soil classification according to Eurocode 8. The results indicated that the sites that are characterized by sandy glaciofluvial, littoral or alluvial sediments fall into category C and the sites where the deposits are cemented to some degree belong to category B. Furthermore, the MASW measurements were used to evaluate the liquefaction potential at a site where liquefaction sand boils were observed during an Mw6.3 earthquake occurring in May 2008. The simplified procedure of assessing cyclic stress ratio to normalized shear wave velocity revealed that liquefaction had occurred down to 3–4 m depth, which is consistent with observations on site.

The seismicity in Iceland is related to the Mid-Atlantic plate boundary which crosses the country from north to south. Since 1700, there have been 25 earthquakes of magnitude six or greater in the two major seismic zones in Iceland. For many of the historical earthquakes (older than 100 years), detailed written descriptions are available that describe the damage from farm to farm. For the most recent earthquakes, like the two south Iceland earthquakes of June 2000 and the south Iceland earthquake of May 2008, comprehensive building-by-building loss data exist. The loss data in these cases are split into a number of subcategories of structural and non structural damage. The building stock in south Iceland has changed significantly from 1700 to the present. For ages, vulnerable turf and stone houses dominated, but in the twentieth century, concrete buildings and timber buildings took over. Seismic codes were implemented in 1976 and have gradually improved the seismic capacity of present building stock. In this book chapter, an overview of the seismic performance of old and new Icelandic buildings is given. Observed and reported damage caused by three earthquake sequences and a single event are discussed; first, the damage caused by two earthquakes in August 1784 in south Iceland; then, by the 1896 earthquake sequence in south Iceland; then, the damage after a single event in 1934 in north Iceland; and finally, the loss data from the 2000 and 2008 earthquakes in south Iceland. The main focus is on the last three events for which most of the data exist.

All buildings in Iceland are registered in an official database that contains detailed information about them, and insurance against natural disasters is obligatory. When a destructive earthquake occurs, all damage is reported, and the repair and replacement cost for every affected building is evaluated. In May 2008, a shallow earthquake of magnitude Mw = 6.3 struck in South Iceland. A great deal of damage occurred, but fortunately, there was no loss of life. The recorded maximum PGA was 0.88 g. Detailed and complete information of all real estate property and the damage incurred, along with recorded strong-motion data and an area-specific attenuation model, have provided an opportunity to create probabilistic damage curves for the building stock in the affected area. The damage model obtained from the 2008 earthquake was tested and verified by using it to back-calculate the damage that occurred in the two South Iceland earthquakes of June 2000 ( Mw = 6.5).

The South Iceland Lowland is an active seismic zone. In May 2008 a magnitude 6.3 (Mw) earthquake struck the area. The 370-m-long base-isolated Oseyrar Bridge situated close to the epicentre was hit by strong ground motion. Concrete stoppers at the top of all piers were badly smashed and all four wing walls of the abutments were severely damaged. The study showed that it is possible with numerical models to back-calculate the observed damage based on recorded ground motion in the area. The recorded loads were larger than prescribed by Eurocode 8 for the site even though the magnitude and location of the earthquake was as expected. The main reason was a near-fault pulse which is not covered in the code. The pulse dominated the bridge response and is therefore important to consider. Finally, an improved design is presented that could have prevented the damage.

Since 1983, 12 Icelandic bridges have been base isolated for seismic protection. Lead-rubber bearings have been used in all the cases. The Thjorsa River Bridge, built in 1950 and retrofitted with base isolation in 1991, is instrumented by strong-motion accelerometers. The bridge has one 83-m-long main span and two 12-m-long approach spans. Only the main span, a steel arch truss with concrete deck, is base isolated. In June 2000, two major earthquakes of magnitude 6.6 and 6.5 occurred in South Iceland; the epicenter was close to the Thjorsa River Bridge. In the first earthquake, a peak ground acceleration of 0.53 g was recorded at the bridge site, and in the second earthquake, a peak ground acceleration of 0.84 g was recorded. The Thjorsa River Bridge survived the earthquakes without any serious damage and was open for traffic immediately after the earthquakes.

Seismicity and volcanic activity in Iceland are related to the Mid-Atlantic plate boundary that crosses the island. Due to volcanic activity, different sea levels through the ages and glacial drift, the geology in Iceland is quite complex at many sites. In June 2000, two major earthquakes of magnitude 6.6 (Mw) and 6.5 (Mw) occurred in southern Iceland. Ground motion from these main shocks and a number of aftershocks were recorded at the Icelandic strong motion network operated by the University of Iceland. At one of the instrumented sites considerable amplification was recorded on lava-rock overlying alluvial deposits. This site fits poorly in the soil classification systems of most earthquake codes. In this paper the recorded data is analyzed with different methods and the results are compared with the results of a one-dimensional site response analysis. The different methods produce the same characteristic of soil amplification at the site. The findings of this study have important implications for design criteria for sites with similar geology. q 2002 Elsevier Science Ltd. All rights reserved.

The road along the Óshlíð hillside in the West Fjords region of Iceland is one of the most hazardous roads in Iceland due to avalanches, rockfalls and debris flows. The road has little traffic, but nevertheless traffic accidents caused by the severe conditions at the site are common. A number of avalanche tracks are found on the hillside. In some of these tracks, avalanches occur more frequently than in others. When there is an avalanche threat, avalanches generally flow over many tracks in a short time. Monitoring vibrations in the tracks with the highest avalanche frequency can indicate when avalanches start flowing down the hillside in a snowstorm, and avalanche hazard can then be declared with the specific site indicated. The same methodology can be used for rockfalls and debris flows, which are strongly affected by weather conditions and typically occur in clusters. Based on this knowledge, a research project was initiated in February 1996 with the objective of developing an automatic system based on seismic measurements to detect and analyze avalanches on the Óshlíð hillside and to instantly send a warning to a control station.