HYPOSAT – An Enhanced Routine to Locate Seismic Events

Schweitzer, Johannes

doi:10.1007/pl00001160

Cited by 150 publications

(70 citation statements)

References 19 publications

(5 reference statements)

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“…As a result of the stability investigation, the 2-4 Hz fixed frequency band was selected for all f-k calculations. The location estimates were made using the HYPOSAT program (SCHWEITZER, 2001a) and are displayed in Fig. 8 together with location estimates made by three different procedures.…”

Section: Case Study: Ammunition Destruction Explosions In Northern Fimentioning

confidence: 99%

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

Gibbons

Kværna

Ringdal

2009

Pure Appl. Geophys.

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The global monitoring of earthquakes and explosions at decreasing magnitudes necessitates the fully automatic detection, location and classification of an ever increasing number of seismic events. Many seismic stations of the International Monitoring System are small-aperture arrays designed to optimize the detection and measurement of regional phases. Collaboration with operators of mines within regional distances of the ARCES array, together with waveform correlation techniques, has provided an unparalleled opportunity to assess the ability of a small-aperture array to provide robust and accurate direction and slowness estimates for phase arrivals resulting from well-constrained events at sites of repeating seismicity. A significant reason for the inaccuracy of current fully-automatic event location estimates is the use of f-k slowness estimates measured in variable frequency bands. The variability of slowness and azimuth measurements for a given phase from a given source region is reduced by the application of almost any constant frequency band. However, the frequency band resulting in the most stable estimates varies greatly from site to site. Situations are observed in which regional P-arrivals from two sites, far closer than the theoretical resolution of the array, result in highly distinct populations in slowness space. This means that the f-k estimates, even at relatively low frequencies, can be sensitive to source and path-specific characteristics of the wavefield and should be treated with caution when inferring a geographical backazimuth under the assumption of a planar wavefront arriving along the great-circle path. Moreover, different frequency bands are associated with different biases meaning that slowness and azimuth station corrections (commonly denoted SASCs) cannot be calibrated, and should not be used, without reference to the frequency band employed. We demonstrate an example where fully-automatic locations based on a source-region specific fixedparameter template are more stable than the corresponding analyst reviewed estimates. The reason is that the analyst selects a frequency band and analysis window which appears optimal for each event. In this case, the frequency band which produces the most consistent direction estimates has neither the best SNR or the greatest beam-gain, and is therefore unlikely to be chosen by an analyst without calibration data.

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Section: Case Study: Ammunition Destruction Explosions In Northern Fimentioning

confidence: 99%

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

Gibbons

Kværna

Ringdal

2009

Pure Appl. Geophys.

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“…An evaluation of several available crustal models was therefore performed. Observed and theoretical travel times for two models are shown in Figure 3, plotted according to epicentral distance after relocation with the corresponding model using HYPOSAT (SCHWEITZER, 2001). All depths were fixed at 10 km for this comparison.…”

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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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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“…For the determination of the hypocentral parameters we use HYPOSAT (Schweitzer 2001) and an average velocitydepth model for Baden-Württemberg (Stange and Brüstle 2005). As input data we carefully picked P-and SH-wave arrival times on the vertical and transverse components, respectively.…”

Section: Hypocenter Determinationmentioning

confidence: 99%

“…Using HYPOSAT (Schweitzer 2001) with first P-and SHwave arrivals at 36 stations we found 49.375 ± 0.009°N and 8.430 ± 0.013°E as epicentral coordinates. This location is about 5 km north of Speyer, just west of the village of Otterstadt.…”

Section: Hypocenter Determinationmentioning

confidence: 99%

The 2005 Heidelberg and Speyer earthquakes and their relationship to active tectonics in the central Upper Rhine Graben

Ritter

Wagner

Bonjer

et al. 2007

Int J Earth Sci (Geol Rundsch)

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We determine the source parameters of three minor earthquakes in the Upper Rhine Graben (URG), a Cenozoic rift, using waveforms from permanent and temporary seismological stations. Two shallow thrust-faulting events (M L = 2.4 and 1.5) occurred on the rift shoulder just south of Heidelberg in March 2005. They indicate a possible movement along the sediment-crystalline interface due to tectonic loading from the near-by Odenwald. In February 2005, an earthquake with a normal-faulting mechanism occurred north of Speyer. This event (M L = 2.8) had an unusual depth of about 22 km and a similar deep normal-faulting event occurred there in 1972 (M L = 3.2). Other lower crustal events without fault plane solutions are known from 1981 and 1983. At such a depth, inside the lower crust, ductile behaviour instead of brittle faulting is commonly assumed and used for geodynamic modelling. Based on the newly available fault plane solutions we can confirm the brittle, extensional regime in the upper and lower crust in the central to northern URG indicated in earlier studies.

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HYPOSAT – An Enhanced Routine to Locate Seismic Events

Cited by 150 publications

References 19 publications

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

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

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

The 2005 Heidelberg and Speyer earthquakes and their relationship to active tectonics in the central Upper Rhine Graben

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