Mechanisms of Earthquakes in Iceland

Einarsson, Páll

doi:10.1007/978-3-642-36197-5_298-1

Cited by 9 publications

(4 citation statements)

References 33 publications

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“…habited areas. For the past decades a major effort has been devoted to the mapping of surface expressions of earthquake faults in Iceland, and these often indicate the location of historical earthquakes (Einarsson, 2015). Furthermore, the main faults tend to produce microearthquakes detected with the SIL network.…”

Section: Combining Cataloguesmentioning

confidence: 99%

A harmonised instrumental earthquake catalogue for Iceland and the northern Mid-Atlantic Ridge

Jónasson

Bessason

Helgadóttir³

et al. 2021

Nat. Hazards Earth Syst. Sci.

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Abstract. 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).

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Section: Combining Cataloguesmentioning

confidence: 99%

A harmonised instrumental earthquake catalogue for Iceland and the northern Mid-Atlantic Ridge

Jónasson

Bessason

Helgadóttir³

et al. 2021

Nat. Hazards Earth Syst. Sci.

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“…Iceland is the most seismically active country in northern Europe, situated on the Mid-Atlantic Ridge, where the extensional margin of the Eurasian and North American tectonic plates interacts with the Icelandic mantle plume. Historically, the largest earthquakes in Iceland occur in the two large transform zones: the South Iceland Seismic Zone (SISZ) and the Reykjanes Peninsula Oblique Rift (RPOR) located in Southwest Iceland; as well as the offshore Tjörnes Fracture Zone (TFZ) in northern Iceland (Figure 1a) (Einarsson 2014). Therefore, these are the regions of highest seismic hazard in the country (Figure 1a), codified as having a 10% probability in 50 years that the reference peak ground acceleration (PGA) exceeds 0.5 g (the standard acceleration due to Earth's gravity, equivalent to g-force) (Standards Council of Iceland, 2010).…”

Section: Introductionmentioning

confidence: 99%

“…The SISZ is collocated with a relatively densely populated agricultural region and contains all critical infrastructures and lifelines of modern society. It is also capable of producing large earthquakes such as the 1912 𝑀 w 7.0 earthquake in the eastern SISZ, with the most recent ones are the June 2000 𝑀 w 6.4 and 𝑀 w 6.5 earthquakes and the 29 May 2008 𝑀 w 6.3 earthquake (see yellow stars in Figure 1a) (Einarsson 1991(Einarsson , 2008(Einarsson , 2014. The TFZ, which is a largely offshore seismic zone with a relatively small population located at long distance from the faults, is believed to experience numerous earthquakes, with magnitudes up to 7.0 (Stefansson et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Nationwide frequency-dependent seismic site amplification models for Iceland

Darzi,

Halldorsson,

Cotton

et al. 2024

Soil Dynamics and Earthquake Engineering

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“…Due to the eastward ridge-jump of the extensional plate boundary on land in Iceland, two large transform zones have been formed: The complex and extensive Tjörnes Fracture Zone mostly offshore North Iceland, and the Southwest Iceland transform zone, comprising the SISZ and the RPOR. Historically, the largest earthquakes in Iceland of 𝑀 w ~ 7 have repeatedly taken place in these transform zones according to historical annals of ~1000 years, teleseismic recordings of ~100 years, and the last ~30 years of local recordings of seismic strong-motions (Tryggvason et al 1958;Einarsson 1991Einarsson , 2008Einarsson , 2014Stefansson et al 2008;Sigbjörnsson et al 2014;Steigerwald et al 2020;Einarsson et al 2020;Jónasson et al 2021). As a result, the SISZ-RPOR is one of two regions in Iceland where the seismic hazard is highest.…”

Section: Introductionmentioning

confidence: 99%

Towards physics-based PSHA using CyberShake in the South Iceland Seismic Zone

Rojas¹,

Rodriguez²,

Puente³

et al. 2021

Preprint

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<p>Traditional Probabilistic Seismic Hazard Analysis (PSHA) estimates the level of earthquake ground shaking that is expected to be exceeded with a given recurrence time on the basis of&#160; historical earthquake catalogues and empirical and time-independent Ground Motion Prediction Equations (GMPEs). The smooth nature of GMPEs usually disregards some well known drivers of ground motion characteristics associated with fault rupture processes, in particular in the near-fault region, complex source-site propagation of seismic waves, and sedimentary basin response. Modern physics-based earthquake simulations can consider all these effects, but require a large set of input parameters for which constraints may often be scarce. However, with the aid of high-performance computing (HPC) infrastructures&#160; the parameter space may be sampled in an efficient and scalable manner allowing for a large suite of site-specific ground motion simulations that approach the center, body and range of expected ground motions.&#160;</p><p>CyberShake is a HPC platform designed to undertake physics-based PSHA from a large suite of earthquake simulations. These simulations are based on seismic reciprocity, rendering PSHA computationally tractable for hundreds of thousands potential earthquakes. For each site of interest, multiple kinematic rupture scenarios, derived by varying slip distributions and hypocenter location across the pre-defined fault system, are generated from an input Earthquake Forecast Model (EFM). Each event is simulated to determine ground motion intensities, which are synthesized into hazard results. CyberShake has been developed by the Southern California Earthquake Center, and used so far to assess seismic hazard in California. This work focuses on the CyberShake migration to the seismic region of South Iceland (63.5&#176;- 64.5&#176;N, 20&#176;-22&#176;W) where the largely sinistral East-West transform motion across the tectonic margin is taken up by a complex array of near-vertical and parallel North-South oriented dextral transform faults in the South Iceland Seismic Zone (SISZ) and the Reykjanes Peninsula Oblique Rift (RPOR). Here, we describe the main steps of migrating CyberShake to the SISZ and RPOR, starting by setting up a relational input database describing potential causative faults and rupture characteristics, and key sites of interest. To simulate our EFM, we use the open source code SHERIFS, a logic-tree method that converts the slip rates of complex fault systems to the corresponding annual seismicity rate. The fault slip rates are taken from a new 3D physics-based fault model for the SISZ-RPOR transform fault system. To validate model and simulation parameters, two validation steps using key CyberShake modeling tools have been carried out. First, we perform simulations of historical earthquakes and compare the synthetics with recorded ground motions and results from other forward simulations. Second, we adjust the rupture kinematics to make slip distributions more representative of SISZ-type earthquakes by comparing with static slip distributions of past significant earthquakes. Finally, we run CyberShake and compare key parameters of the synthetic ground motions with new GMPEs available for the study region. The successful migration and use of CyberShake in South Iceland is the first step of a full-scale physics-based PSHA in the region, and showcases the implementation of CyberShake in new regions.</p>

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Mechanisms of Earthquakes in Iceland

Cited by 9 publications

References 33 publications

A harmonised instrumental earthquake catalogue for Iceland and the northern Mid-Atlantic Ridge

A harmonised instrumental earthquake catalogue for Iceland and the northern Mid-Atlantic Ridge

Nationwide frequency-dependent seismic site amplification models for Iceland

Towards physics-based PSHA using CyberShake in the South Iceland Seismic Zone

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