Robust regional phase association

Abstract

The need for the rapid association of earthquake phase arrivals arises as one of the major requirements of rapid notification systems. The primary goal of an earthquake early warning system is to warn critical facilities of impending strong ground shaking after rupture in the source region has commenced, but before the arrival of seismic energy (Heaton, 1985;Ellsworth and Heaton, 1994). Recent advances in computer and communications technology make such systems both feasible and practical. Toward this end a phase association algorithm, based on stacking the time-reciprocal regional travel-time function, has been developed; forming the basis of the Auryn phase associator. Earthquake catalogs are adjusted, and locations are recalculated, in real-time as each phase is received. The design is such that hypocenters can be calculated and plotted during vigorous swarms and aftershock sequence.Future potential applications include shortening of the alarm times prior to large earthquakes, processing amplitude data along with phase arrivals, providing a more robust method of associating phase from sparse regional networks (with possible application to nuclear test ban monitoring, and the association of teleseismic phases from global networks.

Open-Source ANSS Quake Monitoring System Software

“…Figure 2 illustrates the data flow in a minimal AQMS system. It uses Earthworm to generate subnet coincident triggers via carlstatrig-carlsubtrig (see Data and Resources) as well as more selective binder events (Johnson et al, 1997) that get funneled through the earthworm mega-module (sometimes referred to as "the sausage") into Hypoinverse (Klein, 2002). Earthworm can be configured with many different rings.…”

“…Earthworm at the Base AQMS uses the Earthworm (Johnson et al, 1995;Olivieri and Clinton, 2012) automatic processing system. Written in the C programming language, Earthworm provides multiple waveform processing modules, multiple phase pickers (e.g., pick_ew, pick_FP, coda_picker, carlstatrig), a ground-motion parameters module (gmew), a local magnitude algorithm (localmag), one subnet coincidence trigger (carlsubtrig) event detector, and one event detector and pick associator named binder_ew (Johnson et al, 1997). To obtain refined hypocenter locations, Earthworm can be configured to run the Hypoinverse (Klein, 2002) or NonLinLoc (Lomax et al, 2000(Lomax et al, , 2009) earthquake locators.…”

Continuous Kurtosis-Based Migration for Seismic Event Detection and Location, with Application to Piton de la Fournaise Volcano, La Reunion

“…After a large mainshock (e.g., M ≥ 6) or during a volcanic swarm, a cascade of earthquakes inundates the acquisition/detection system with multiple, near-simultaneous events in different parts of the affected area. In such conditions, procedures based on phase picks and event association are often known to fail (e.g., Johnson et al, 1994). As a result, many of these events may be either falsely associated and mislocated or missed altogether.…”

Earthquake/noise discrimination and estimation of P-S phases based on wave characteristics

“…The waveform attributes (amplitude, frequency, polarization) are used for the seismogram characterization. The well known STA/LTA (short-term-average longterm-average) algorithm (Allen 1978(Allen , 1982 applied on an envelope function sensitive to both amplitude and frequency of seismograms still comprises part of Earthworm (Johnson et al 1994) and Sac2000 (Goldstein et al 1999).…”