István Bondár

Collection of a Reference Event Set for Regional and Teleseismic Location Calibration

A three-year consortium project, with members of Science Applications International Corp., University of Colorado at Boulder, Harvard University, Multimax Inc., Geophysical Institute of Israel, Western Services, and University of California at San Diego, was initiated in 2000 to improve locations and reduce uncertainties in the Middle East, North Africa, Europe, and Western Eurasia. The consortium developed high-resolution three-dimensional models of the Earths mantle to generate accurate travel-time predictions for regional and teleseismic P phases. Since the approach was purely model-based, a large set of high-quality reference events was needed to validate the model predictions. The consortium has spent considerable effort to collect, vet, and validate reference events located with 5-km accuracy or better by local networks and “promoted” reference events located with an accuracy of 7 km or better by application of multiple-event location techniques. Consortium members built an extensive network of contacts to solicit candidate reference events from local, regional, and national network operators. Strict methodologies were developed to identify candidate reference events in earthquake bulletins, and to validate and quality control the selected candidate reference events. The outcome of the consortium effort was a quality-controlled reference event list with nearly 2000 events and over 200,000 arrivals. The Reference Event List is provided as an electronic supplement to this article. Online material : Reference event database. Manuscript received 23 June 2003.

Development of calibration techniques for the Comprehensive Nuclear-Test-Ban Treaty (CTBT) international monitoring system

Abstract A prototype International Data Centre (pIDC) is developing and testing concepts for the International Monitoring System that will be put into place to monitor compliance with the recently-signed Comprehensive Test Ban Treaty (CTBT). The testing includes the routine production of a daily bulletin of global seismic activity, several days after real time, since the beginning of 1995. A wider variety of seismic phases are used for location than is the practice of existing agencies producing global bulletins at greater delays, and another difference is that observed slowness vectors are used in addition to arrival time. Comparisons of pIDC bulletins with those provided by national agencies that operate denser networks have demonstrated both random and systematic errors in location that often exceed the formal error estimates. The pIDC is developing and testing techniques to reduce systematic biases through region- and path-dependent corrections to travel-time and slowness, and to better account for random errors. Initial results from this very long-term project are encouraging.

Upper Crustal Velocity Structure in Slovenia from Rayleigh Wave Dispersion

Abstract—The inversion of surface-wave dispersion curves can provide information on the average elastic properties of the upper crustal layers that are usually poorly sampled by body waves. The broad band digital records of earthquakes which recently occurred in Slovenia and neighbouring regions are used to extract the group velocity of the fundamental mode of Rayleigh waves, using frequency-time analysis (FTAN). The obtained dispersion curves permit a good resolution for the velocity and the thickness of the upper crust. The thickness of the uppermost sedimentary layer varies between 4 and 6 km and its shear-wave velocity is less than 3 km/s. The lower sedimentary layer is 7 to 9 km thick and its shear-wave velocity ranges from about 3.05 km/s in eastern Slovenia, to about 3.25 km/s in western Slovenia. The shear-wave velocity in the crystalline layer is around 3.5 – 3.7 km/s in the eastern part, while in the western part it reaches a rather high value of about 3.85 km/s.

AlpArray in Hungary: temporary and permanent seismological networks in the transition zone between the Eastern Alps and the Pannonian basin

In the last few decades dense large-scale seismic networks showed their importance in studying the structure of the lithosphere and the upper mantle. The better understanding of the Apennines–Alps–Carpathian–Dinarides system is the main target of the AlpArray European international initiative in which more than 50 institutes are involved. The core of AlpArray is the AlpArray Seismic Network (AASN). With its

Teleseismic slowness-azimuth station corrections for the International Monitoring System Seismic Network

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Improved Event Location Uncertainty Estimates

∼600 broadband seismic stations (

Global Ground Truth Data Set with Waveform and Improved Arrival Data

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