Enhancement of the Strong Motion and Seismic Network in Turkey
SfP-Seismic Assessment 977484
No one can be sanguine that any array will capture its intended information
immediately after being established. Forecasting of earthquakes is
rife with much uncertainty, and an early maxim in strong motion seismology
stated that earthquakes tended to cease occurring in areas that had
been instrumented to record them! In spite of this seeming initial
setback many arrays have been created in many different countries,
and useful data recorded for the benefit of the world community of
scientists and engineers. There must be a reasonable expectation that
an earthquake can be recorded within a meaningful length of time,
and that the records will be representative of the seismic environment
that produced them.
Some current research indicates that there exist plausible grounds
to expect heightened odds for a major earthquake to affect Istanbul,
the largest city in Turkey, and the principal seat of the countrys
financial institutions.14 This forecast considers earthquakes on the
North Anatolian fault system in the Sea of Marmara during the past
5000 years, and tests the resulting catalog against the frequency
of damage in the city during the preceding millennium. If the time-dependent
effect of stress transferred by the 1999 Mw = 7.4 Izmit earthquake
to faults nearer to the city are considered, then there appears to
be a 32 percent probability of strong shaking to occur within 50 km
from Istanbul during the next decade. The ground rupture during the
17 August 1999 earthquake appears to have terminated beneath the Marmara
Sea to the east of Yalova, thus increasing the stress and the likelihood
of a triggering there. Yalova is 40 km to the south-east of Istanbul.
There are no seismic faults within the immediate vicinity of Istanbul.
It is therefore prudent to set up the first array in the area of Yalova,
containing the urban boundaries from east to west, but extending beyond
them transversely and longitudinally.