Local magnitude estimate

The phase catalogue maintains the original information on the event duration at each station. Durations are strongly heterogeneous mainly because of its different definition among operators.
We decided to use only durations provided by INGV national network because of its homogeneity through time. We derive local magnitude via linear regression between manual estimates of local magnitudes provided by MedNet network and the corresponding durations.
We then could work with a dataset of 5,000 Ml, with a good coverage of the Italian territory, ranging from 1.9 up to 6.0, but with a large concentration in the range 2.5-4.0.

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The empirical relationship linking the log of duration with Richter magnitude is M = a + b∙log(T), with a and b depended of investigated area according to the observation that Md is practically independent of hypocentral distance for short distance ranges We could differentiate the behaviour of stations located in the peninsula from those located in Sicily for which we determined large station residuals (Castello et al., 2007).
The regressions are defined in the interval 1.5-4.5. Ml for larger earthquakes is not derived from regression but is either estimated from MedNet data, or from scientific literature, or from NEIC bulletins. Such information is reported in the catalogue. Deep earthquakes have either Mw or Mb (Castello et al., 2007).

In summary, the earthquake catalogue 1981-2002 contains 46,574 Ml estimates above 1.5. The earthquake catalogue will be released on a CD-ROM