Article

An automatic, adaptive algorithm for refining phase picks in large seismic data sets

Bulletin of the Seismological Society of America (Impact Factor: 1.94). 06/2002; 92:1660-1674. DOI: 10.1785/0120010224

ABSTRACT We have developed an adaptive, automatic, correlation- and clustering-based method for greatly reducing the degree of picking inconsistency in large, digital seismic catalogs and for quantifying similarity within, and discriminating among, clusters of disparate waveform families. Innovations in the technique include (1) the use of eigenspectral methods for cross-spectral phase estimation and for providing subsample pick lag error estimates in units of time, as opposed to dimensionless relative scaling of uncertainties; (2) adaptive, cross-coherency-based filtering; and (3) a hierarchical waveform stack correlation method for adjusting mean intercluster pick times without compromising tight intracluster relative pick estimates. To solve the systems of cross-correlation lags we apply an iterative, optimized conjugate gradient technique that minimizes an L1-norm misfit. Our repicking technique not only provides robust similarity classification-event discrimination without making a priori assumptions regar

1 Bookmark
 · 
122 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Hypocenter locations of shallow earthquakes in Horonobe area, northern Hokkaido, Japan, which is near the convergent boundary between Okhotsk and Amuria plates, were determined to reveal the subsurface structure and the mechanisms of earthquake occurrence. The absolute source locations of 211 earthquakes which occurred in the period from December 2002 to September 2005 were determined; then, those earthquakes with similar waveforms were identified, and the source locations of 26 multiplet groups were relocated by using cross-spectrum and clustering analyses. The relocated hypocenters allowed two seismically active areas to be identified, at 10–20 km and 25–30 km depth. The earthquake locations indicate structures trending nearly N-S direction, and the structures causing repeated stick-slips at asperities, thus generating similar earthquakes. The relationships between magnitude and the distance to the next event, and between magnitude and the time interval of event occurrences were investigated. The relationships between them suggest that earthquake swarms would be induced by continuous strain accumulation at asperities along faults and its subsequent release as a result of plate tectonic movements. A cutoff line could be also seen in the relationship between magnitude and the distance to the next event, suggesting that the distance between the source locations depends on the event magnitude. These results have given us the knowledge that the asperities on the delineated faults intermittently release strain energy as similar earthquakes with magnitudes of less than about 3.0.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: On 2 June 2006 the wastewater produced during the oil and gas field exploitation in High Agri Valley (southern Italy) started to be managed by disposal through pumping the fluids back into the subsurface at the Costa Molina 2 (CM2) injection well, located in the southeastern sector of the valley. The onset of microearthquakes (Ml ≤ 2) after 4 days at about 1.3 km SW of CM2 well suggests fluid-injection induced seismicity by the diffusion of pore pressure. Moreover, the space-time evolution of 196 high-resolution relocated events reveals a previously unmapped NE dipping fault. We investigate the physical processes related to the fluid injection induced seismicity and delineate the previously unmapped fault by jointly analyzing seismicity data, geological observations, fluid injection data, the stratigraphic log of the CM2 well, and the electrical resistivity tomography survey carried out in the study area.
    Geophysical Research Letters 08/2014; 41(16):5847–5854. · 3.98 Impact Factor
  • Source
    2ECEES, At Istanbul, Turkey; 08/2014

Full-text (2 Sources)

Download
51 Downloads
Available from
Jun 2, 2014