Geography Reference
In-Depth Information
(Figure 3) represents a set of interacting program units: a seismological
database, a geographical subsystem, and a subsystem for data analysis.
The seismological DB
lying at the base of the system contains 63 catalogs
of historical and instrumental earthquakes, among which both the catalogs
from known agencies and geophysical surveys, and the authors' own catalogs
representing incorporated and filtered data collected from various sources. The
reasons for using several catalogs are as follows. First, this allows dealing with
both global- and local-scale (world and regional catalogs, respectively)
earthquake data. Second, by comparing different geographically overlapping
catalogs in terms of completeness, with the use of the EEDB methods
(earthquake frequency histograms and plotted time series of magnitudes), one
can divide the map into zones (―
regions
‖) and select the respective preferable
catalogs (Figure 4).
We most often use global catalogs (e.g., NEIC, 1973 to present, and
SIGN, -2000 to 1993, of the American Geophysical Survey, USGS) and
regional catalogs, such as the Baikal catalog (BAIK in sequel, in which 87%
of data belong to the Baikal Branch of Geophysical Survey (GS) SB RAS,
available at http://www.seis-bykl.ru) and the Altai catalog (Altay-Sayan
Branch of GS SB RAS). The overlapping boundaries of catalog
completenesses we revealed for the case of the BAIK catalog are even wider
than those indicated by the authors of the GS catalogs (Figure 4) [25, 26].
Figure 5. Earthquake catalog format.
The format of the earthquakes contains fields with key source parameters:
energy, magnitude, epicenter size (length), origin time, location (coordinates),
and depth (Figure 5). The released seismic energy is the principal
characteristic, which may be expressed either on the magnitude or on energy
scales. Most catalogs worldwide (e.g., NEIC) use the magnitude scale based
on body waves (
mb
) while Russian catalogs use the energy scale (e.g., that for
