Publication Date:
2017-04-04
Description:
To learn about recurrence of large earthquakes and strain model on
the Düzce segment of the North Anatolian Fault Zone, that ruptured on
November, 12, 1999 (Mw 7.1), systematic geomorphological and
paleoseismological analyses were integrated.
In order to provide new estimates on Quaternary slip rate of the
fault., geo-morphological mapping along the fault trace permitted to analyze
fault-related cumulative landforms and drainage pattern settings. Remnant
of an old alluvial fan modeled by fluvial terraces and 41 right-hand stream
deflections were reconstructed, described and used as offset geomorphic
markers. Two correlated Late Pleistocene, terrace risers, offset of about 300
and 900 m, respectively, were dated by means of OSL method about 21 kyr
BP and 60 kyr BP. Moreover, the onset of the offset of the streams deflected
for a total of 100 m was radiocarbon dated about 7000 yr BP. These data
translate to a constant rate of deformation of 15.0±3.2 mm/yr for the last 60
kyr. On the basis of “characteristic-earthquake model” and under constant
slip rate assumptions, it is possible to estimate that stream deflections across
the Düzce Fault may be explained by repetition of 20-30 1999-like
earthquakes during the last 7000 years, thus the recurrence time for surface
rupturing events of the Düzce Fault is 290±60 years.
With the aim to reconstruct the record of last large earthquakes, 10
trenches at five sites were excavated. By merging information obtained from
all trenches, evidence for three surface faulting earthquakes prior to 1999
were found. These paleoearthquakes are dated on the basis of radiocarbon,
210Pb and archaeological information and can be summarized at: 1)
AD1685-1900, possibly end of 19th century; 2) AD1685-1900, possibly close to AD1700; 3) AD800-1000. Some of them can be correlated to
historical earthquakes occurred on AD967, 1719, 1878 or 1894. These
paleoseismological results, merged with those from previous papers, are
suggestive of bimodal recurrence distribution yielding overall average
recurrence time of ~350 yrs for the past two millennia, compatible with that
calculated from the geomorphic markers analysis. Under the assumption of
“characteristic earthquake”, bimodal paleoearthquakes distribution indicate
slip rate fluctuations during the past two millennia, with clustered high
strain release. These results suggest Wallace-type strain release model for
the Düzce fault, and average strain accumulation of 11.4±1.2 mm/yr, in
agreement with slip rate results for the past 60 kyr obtained by geomorphic
marker analysis.
Description:
Submitted
Description:
3.2. Tettonica attiva
Description:
open
Keywords:
geochronology
;
geomorphology
;
Duzce
;
Turkey
;
04. Solid Earth::04.04. Geology::04.04.01. Earthquake geology and paleoseismology
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
book chapter
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