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  • 1
    Electronic Resource
    Electronic Resource
    Comparison of Absolute and Relative Moment Tensor Solutions For The January 1997 West Bohemia Earthquake Swarm (2000)
    Springer
    Studia geophysica et geodaetica 44 (2000), S. 233-250 
    Details
    ISSN: 1573-1626
    Keywords: West Bohemia/Vogtland region ; earthquake swarm ; multiple event ; focal mechanisms ; moment tensor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Abstract Moment tensor solutions for 70 clustered events of the 1997 West Bohemia microearthquake swarm, as calculated by two different methods, are given. The first method is a single-event, absolute moment tensor inversion which inverts body-wave peak amplitudes using synthetic Green functions. The second method is a multiple-event, relative method for which Green functions are “reduced” to 2 geometrical angles of rays at the sources. Both methods yield similar moment tensors, which can be divided into at least two or three different classes of focal solutions, indicating that, during the swarm activity, different planes of weakness were active. The major source component of most events is a double couple. However, the deviations from the double-couple mechanisms seem to be systematic for some classes of solutions. Error analysis was based on transforming the estimate of the standard deviation of amplitudes extracting from the seismograms into confidence regions of the absolute moment tensor. They show that the non-DC components are significant at a fairly high confidence level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022166926987
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    Paper (German National Licenses)
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  • 2
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    A probabilistic approach for the classification of earthquakes as ‘triggered’ or ‘not triggered’ (2020)
    Springer
    Details
    Publication Date: 2020-12-15
    Description: The occurrence time of earthquakes can be anticipated or delayed by external phenomena that induce strain energy changes on the faults. ‘Anticipated’ earthquakes are generally called ‘triggered’; however, it can be controversial to label a specific earthquake as such, mostly because of the stochastic nature of earthquake occurrence and of the large uncertainties usually associated to stress modelling. Here we introduce a combined statistical and physical approach to quantify the probability that a given earthquake was triggered by a given stress-inducing phenomenon. As an example, we consider an earthquake that was likely triggered by a natural event: the M = 6.2 13 Jan 1976 Kópasker earthquake on the Grímsey lineament (Tjörnes Fracture Zone, Iceland), which occurred about 3 weeks after a large dike injection in the nearby Krafla fissure swarm. By using Coulomb stress calculations and the rate-and-state earthquake nucleation theory, we calculate the likelihood of the earthquake in a scenario that contains only the tectonic background and excludes the dike and in a scenario that includes the dike but excludes the background. Applying the Bayes’ theorem, we obtain that the probability that the earthquake was indeed triggered by the dike, rather than purely due to the accumulation of tectonic strain, is about 60 to 90 %. This methodology allows us to assign quantitative probabilities to different scenarios and can help in classifying earthquakes as triggered or not triggered by natural or human-induced changes of stress in the crust.
    Description: Published
    Description: 165–187
    Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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