HR: 1340h
AN: S43B-1076    [Abstracts]
TI: Apparent Clustering and Apparent Background Earthquakes Biased by Undetected Seismicity
AU: * Werner, M J
EM: mwerner@ucla.edu
AF: Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, UCLA, 595 Charles Young Dr E, Los Angeles, CA 90095 United States
AU: Sornette`, D
EM: sornette@moho.ess.ucla.edu
AF: Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, UCLA, 595 Charles Young Dr E, Los Angeles, CA 90095 United States
AU: Sornette`, D
EM: sornette@moho.ess.ucla.edu
AF: Laboratoire de Physique de la Matiere Condensee, CNRS UMR6622, Universite de Nice - Sophia Antipolis, Parc Valrose, Nice Cedex 2, 06108 France
AB: In models of triggered seismicity and in their estimation from empirical data, the detection threshold m_d is commonly equated to the magnitude m_0 of the smallest triggering earthquake. This unjustified assumption neglects the possibility of shocks below the detection threshold triggering observable events. We introduce a formalism that distinguishes between the detection threshold m_d and the minimum triggering earthquake m_0 ≤ m_d. By considering the branching structure of one complete cascade of triggered events, we derive the apparent branching ratio n_a (which is the apparent fraction of aftershocks in a given catalog) and the apparent background source S_a observed when only the structure above the detection threshold m_d is known due to the presence of smaller undetected events capable of triggering larger events. If, as several recent analyses have shown, earthquake triggering is controlled in large part by the smallest magnitudes, this implies that previous estimates of the clustering parameters may significantly underestimate the true values: for instance, an observed fraction of 55% of aftershocks is renormalized into a true value of 75% of triggered events.
DE: 3235 Persistence, memory, correlations, clustering (3265, 7857)
DE: 3265 Stochastic processes (3235, 4468, 4475, 7857)
DE: 4468 Probability distributions, heavy and fat-tailed (3265)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 7294 Seismic instruments and networks (0935, 3025)
SC: Seismology [S]
MN: Fall Meeting 2005