Geography Reference
In-Depth Information
Figure 9. Spatial distribution of cumulative rupture density
K
avg
for
Ms
= 2.0-4.5 events
in 1964 through 2007: Altai-Sayan area, lat. 46-52° N; long. 82-91.35° E (top panels),
cell size 0.30.5º; area of Chuya earthquake of 27.09.2003 (bottom panel), cell size
0.20.3º. The maps present the data at every 10 years.
Cluster analysis programs
allow plotting time series of the number of
related events (with or without averaging), relationships of the number of
events in clusters vs. total number of events, the conformity of the clustered
events to the Poisson distribution
N(dt)
, etc., or constructing rose diagrams of
cluster azimuths.
Detecting and analyzing clusters of related events shows the distribution
of seismicity in space while comparing the seismicity patterns in different
periods of time traces the history of the seismic process.
The EEDB system uses several methods to reveal earthquake clusters:
•
introduction of space-time parameters
dT
and
dS
;
•
Sobolev's method (calculating
dT
and
dS
automatically proceeding
from the fractal space theory and physics of fracture) [36];
•
estimating earthquake density using Morisita's index [37].
The clusters obtained by the first method are analyzed using jointly the
geoinformation approach (methods of cartography) and elements of graphic
analysis.
For example, changes in faulting activity can be detected from patterns of
small shocks, in several steps:
