A new absolute arrival time data set for Europe

Abstract

S U M M A R YThe main aim of this study is to create a data set of accurate absolute arrival times for stations in Europe which do not report to the International Seismological Centre (ISC). Waveforms were obtained from data centres and temporary experiments and a semi-automatic picking method was applied to determine absolute arrival times for P and S phases. 85 000 arrival times were picked whose distribution of residuals shows generally low standard deviations on the order of 0.5-0.7 s. Furthermore, mean teleseismic station residuals reflect the properties of the underlying crust and uppermost mantle. Comparison to ISC data for matching event-stationphase combinations also confirms the good quality of the new absolute arrival time picks. Most importantly, this data set complements the ISC data as it fills regional data coverage gaps in Europe.Arrival times are routinely reported by many seismological networks to the International Seismological Centre (ISC), resulting in bulletins of millions of arrival times since 1964. Clearly, a wealth of information can be gained from these data regarding the Earth's interior for example by application of traveltime tomography. However, the reporting stations are not distributed equally over the globe therefore leaving gaps, in particular, in the oceans and stable cratonic regions. Furthermore, the quality of these data, which are mostly handpicked, varies greatly .Besides stations included in arrival time bulletins, a large number of seismic stations exist whose waveforms are not used routinely but are sent to data centres for digital storage. For many events included in these waveforms, arrival times were either not picked at all or only with limitations (e.g. a restricted period in time or limited epicentral distance range).Another valuable source of data is provided by temporary experiments. To fill the geographical gaps, many regional experiments were carried out during the last 15-20 yr where spatially dense temporary networks were placed in the field for several months. Often, arrival times for events registered at those arrays were only picked relatively. That means, not the arrival time of a phase onset was determined but the arrival time of the first maximum or minimum after the onset. This procedure has the advantage that observational errors due to high noise levels can be reduced but as a major disadvantage, * Now at: Chevron Energy Technology Company, Houston, TX, USA. arrival times are only obtained with respect to the unknown mean network arrival time for a specific event. Therefore, they cannot be used for event relocation or to obtain absolute velocity information on the crust and mantle below the array. Consequently, obtaining absolute arrival times for events recorded at such stations which do not report arrival times to the ISC can provide new detailed information for high-resolution traveltime tomography.Besides using additional stations, the picks should also be of a consistent good quality as erroneous picks will affect or overprint velocity structur...

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