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

Abstract

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.

Considerations in Phase Estimation and Event Location Using Small-aperture Regional Seismic Arrays

“…1 (see, for example, STORCHAK et al, 2003, for a description of regional phases and nomenclature). The one-dimensional velocity model which provides the best fit for the region is the BAREY model (HICKS et al, 2004), and this model is used to predict travel times when forming the site-specific templates. The Pn phase is the first predicted arrival at ARCES for most of the sites considered.…”

Preliminary Analysis of the 21 February 2008 Svalbard (Norway) Seismic Sequence

“…However, the analyst-reviewed subset that we reprocess includes approximately 250 events of NORSAR's automatic magnitude M GBF larger than 2.0. The magnitudes were recalculated by remeasurement of amplitudes and application of the amplitude-distance relations introduced by Hicks et al (2004). The strongest aftershock had a regional network magnitude of 4.7 (see also Figure 7, left).…”

Detection and Analysis of Near-Surface Explosions on the Kola Peninsula

“…We applied the global ak135 model (KENNETT et al, 1995), the Fennoscandian model (MYKKELTVEIT and RINGDAL, 1981), and the BAREY and BAREZ models (HICKS et al, 2004). For each velocity model, 10,000 different combinations of onset times for initial P and S arrivals at the stations listed in Table 1 were generated at random from the observed distributions as displayed in the right-hand panels of Fig.…”

“…The red circle marks 69.526°N, 31.930°E which is the approximate location indicated by SKORVE (1991) for an air defence site (based upon satellite imagery prior to 1989). The seismic location estimates are made using the BAREY velocity model (HICKS et al, 2004) than of uncertainty in azimuth estimation (see, for example, SZUBERLA and OLSON, 2004). Despite the somewhat poorer slowness resolution, the microbarograph subarray at Apatity provides backazimuth estimates for infrasound signals over a similar range to ARCES, from approximately 345-4°, with a median value of approximately 351°.…”