Focal parameters, depth estimation, and plane selection of the worldwide shallow seismicity with M s ! 7.0 for the period – 1900– 1976

A worldwide seismic catalog of source parameters is an important tool in many geophysical studies.
Such a kind of database is available only since 1977 with the CMT catalog. The main goal of this paper is
to compile a similar catalog for the time period 1900–1976 estimating the focal parameters of shallow
seismicity (depth 70 km) with Ms ! 7.0 (607 events). In particular, this new catalog (FM0076) contains
strike, dip, rake, and depth estimations for 588 earthquakes in the period 1900–1976. At each estimate two
reliability flags are assigned. The first is linked to the availability of data, and the second is given by
comparing focal mechanism estimations and the tectonics of the epicentral area. The estimation procedure
is based on the knowledge of the moment tensor of shallow earthquakes after 1977. From these data, the
new concept of Weighted Cumulative Moment Tensor (WCMT), which represents such a kind of moment
tensor for a mean earthquake in the epicentral area, leads to estimate the focal parameters. The estimation
method is also tested by comparing out our data set for the period 1977–1989 with the CMT one
(91 events). This comparison reveals a good agreement between the two methods and confirms the
reliability of the catalog FM0076.