NEHRP Clearinghouse
 Title
 b Values for Foreshocks and Aftershocks in Real and Simulated Earthquake Sequences.
 File

PB83173765.pdf
 Author(s)
 Knopoff, L.; Kagan, Y. Y.; Knopoff, R.
 Source

National Science Foundation, Washington, DC.,
January 1982,
17 p.
 Abstract
 The differences in b values between foreshock and aftershock sequences can be shown to be a statistically significant property of real earthquake sequences if a sufficiently large number of cases is considered, i.e., if the catalogs are long enough. These differences depend on the particulars of the data processing procedures used to define the sequences, such as spacetime windowing and definition of cutoff magnitude thresholds for completeness of catalogs, as well as other magnitude cutoffs. They are also a statistically significant property of long artificial, or synthetic catalogs in which all subsequent earthquakes are modeled as resulting from a stochastic time delay applied to predecessor earthquakes. As a consequence, the authors make the conjecture that the difference in b values is due to subtle asymmetries in data processing procedures rather than differences in the physical environment before and after a large earthquake.
 Keywords
 Ground motion; Earthquake engineering; Earthquakes; Magnitude; Frequency distribution; Shock waves; Reprints; Statistical data; Seismic waves