Seismic Location Calibration of the European Arctic

Kremenetskaya, Elena; Асминг, В. Э.; Ringdal, Frode

doi:10.1007/978-3-0348-8250-7_9

Cited by 9 publications

(10 citation statements)

References 3 publications

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“…The 'BAREY' model (Table 1) from SCHWEITZER and KENNETT (2002), based on a model for the Barents Sea area from KREMENETSKAYA et al (2001), provides the smallest overall travel-time residuals when locating events within the vicinity of the Barents-and Kara Seas.…”

Section: Discussionmentioning

confidence: 99%

“…3). These two models were adapted from a model developed for the Barents and Kara Seas by KREMENETSKAYA et al (2001) by making minor P-velocity adjustments and varying the P/S ratio in the upper mantle (SCHWEITZER and KENNETT, 2002). The main differences between these two models are the S velocities in the upper mantle, which of course have the greatest effect on regional S phases propagating at these depths (S n ).…”

Section: Crustal Models and Travel Timesmentioning

confidence: 99%

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Travel-times and Attenuation Relations for Regional Phases in the Barents Sea Region

Hicks

Kværna

Mykkeltveit

et al. 2004

Pure and Applied Geophysics

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A database containing 45 events in the Barents Sea region has been compiled and analyzed with the aim of evaluating crustal models, travel-times and attenuation relations in the context of performing regional detection threshold monitoring of this region. The 45 events are mostly located around the circumference of the study area due to the virtually aseismic nature of the Barents Sea itself. Regional P n and S n phases were observable for most events in the database, while P g and L g phases were only observable for events with raypaths that do not cross the tectonic structures in the Barents Sea. This corroborates a number of previous observations of L g -wave blockage within the Barents Sea. Three existing velocity models were evaluated, with a model having slightly lower S velocities than earlier assumed in the upper mantle giving the overall best fit to the observed arrivals. In order to estimate magnitudes, short-term average (STA) and spectral amplitude values were calculated in several frequency bands for all phase arrivals in the database. There were no significant differences between spectral and STA amplitudes, so the latter were used as this parameter is more efficient to calculate in real-time processing. An inversion was performed in order to determine an attenuation relation specific for this region. The resulting magnitudes based on P n , P g , S n and L g phases gave an internally consistent, reasonably stable set of values, which can be calibrated towards any existing global or regional scale.

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Section: Discussionmentioning

confidence: 99%

Section: Crustal Models and Travel Timesmentioning

confidence: 99%

Travel-times and Attenuation Relations for Regional Phases in the Barents Sea Region

Hicks

Kværna

Mykkeltveit

et al. 2004

Pure and Applied Geophysics

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“…The events are listed in Table 1 and shown in Figure 1 together with the station network. Some of the smaller events have been located by KREMENETSKAYA et al (1999).…”

Section: Datamentioning

confidence: 99%

“…The data have been ®ltered in the 4±8 Hz and 8±16 Hz bands. The ®ve events are the two Kara Sea events on 16 August 1997, two mining explosions in Vorkuta south of the station, and a small event at the coast of Novaya Zemlya in 1995 (KREMENETSKAYA et al, 1999).…”

Section: Kara Sea / Northern Urals Eventsmentioning

confidence: 99%

Observed Characteristics of Regional Seismic Phases and Implications for P / S Discrimination in the European Arctic

Ringdal¹

2002

Pure and Applied Geophysics

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Ð In this paper, we use data from seismic stations operated by NORSAR, the Kola Regional Seismological Centre (KRSC) and IRIS to study the characteristics of regional phases in the European Arctic, with emphasis on the P/S ratio discriminant. While the detection and location capability of the regional station network is outstanding, source classi®cation of small seismic events has proved very dicult. For example, the m b = 3.5 seismic event near Novaya Zemlya on 16 August, 1997 has been the subject of extensive analysis in order to locate it reliably and to classify the source type. We consider the application of the P/S discriminant in the context of this event and other events observed at regional distances in the European Arctic. We show that the P/S ratios of Novaya Zemlya nuclear explosions measured in the 1±3 Hz ®lter band scale with magnitude, indicating a need for caution and further research when applying P/S discriminants. Using mainly data from the large NORSAR array, we note that observed P/S amplitude ratios in the European Arctic show large variability for the same source type and similar propagation paths, even when considering closely spaced observation points. This eect is most pronounced at far regional distances and relatively low frequencies (typically 1±3 Hz), but it is also signi®cant on closer recordings (around 10 degrees) and at higher frequencies (up to about 8 Hz). Our conclusion from this study is that the P/S ratio at high frequencies (e.g., 6±8 Hz) shows promise as a discriminant between low-magnitude earthquakes and explosions in the European Arctic, but its application will require further research, including extensive regional calibration and detailed stationsource corrections. Such research should also focus on combining the P/S ratio with other short-period discriminants, such as complexity and spectral ratios.

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“…The development of different regional seismic models to predict traveltimes has been motivated by an interest to locate seismic events in the region, which includes the former Soviet nuclear test site at Novaya Zemlya. Various regional 1‐D velocity models have been proposed and used for seismic event location [e.g., Kremenetskaya et al , 2001; Hicks et al , 2004]. These models differ slightly from each other mainly with respect to their velocities for the upper mantle.…”

Section: Introductionmentioning

confidence: 99%

A probabilistic seismic model for the European Arctic

et al. 2011

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[1] The development of three-dimensional seismic models for the crust and upper mantle has traditionally focused on finding one model that provides the best fit to the data while observing some regularization constraints. In contrast to this, the inversion employed here fits the data in a probabilistic sense and thus provides a quantitative measure of model uncertainty. Our probabilistic model is based on two sources of information: (1) prior information, which is independent from the data, and (2) different geophysical data sets, including thickness constraints, velocity profiles, gravity data, surface wave group velocities, and regional body wave traveltimes. We use a Markov chain Monte Carlo (MCMC) algorithm to sample models from the prior distribution, the set of plausible models, and test them against the data to generate the posterior distribution, the ensemble of models that fit the data with assigned uncertainties. While being computationally more expensive, such a probabilistic inversion provides a more complete picture of solution space and allows us to combine various data sets. The complex geology of the European Arctic, encompassing oceanic crust, continental shelf regions, rift basins and old cratonic crust, as well as the nonuniform coverage of the region by data with varying degrees of uncertainty, makes it a challenging setting for any imaging technique and, therefore, an ideal environment for demonstrating the practical advantages of a probabilistic approach. Maps of depth to basement and depth to Moho derived from the posterior distribution are in good agreement with previously published maps and interpretations of the regional tectonic setting. The predicted uncertainties, which are as important as the absolute values, correlate well with the variations in data coverage and quality in the region. A practical advantage of our probabilistic model is that it can provide estimates for the uncertainties of observables due to model uncertainties. We will demonstrate how this can be used for the formulation of earthquake location algorithms that take model uncertainties into account when estimating location uncertainties.

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Seismic Location Calibration of the European Arctic

Cited by 9 publications

References 3 publications

Travel-times and Attenuation Relations for Regional Phases in the Barents Sea Region

Travel-times and Attenuation Relations for Regional Phases in the Barents Sea Region

Observed Characteristics of Regional Seismic Phases and Implications for P / S Discrimination in the European Arctic

A probabilistic seismic model for the European Arctic

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