A critical examination of near-field accelerograms from the sea of Marmara region earthquakes

Akkar, S
Gulkan, P
In 1999, Turkey was struck by two major earthquakes that occurred 86 days apart on the North Anatolian Fault system. Both earthquakes had right-lateral strike-slip mechanisms with moment magnitudes greater than 7. The number of strong-motion records obtained from the Kocaeli earthquake (17 August 1999, M-w 7.4) was 34. The second event, designated as the Bolu-Duzce earthquake (12 November 1999, M-w 7.2), triggered 20 instruments. Among the records that we have from these earthquakes, seven are from near-source ground-motion data. These records were obtained from the cities of Gebze (GBZ), Yarimca (YPT), Izmit (IZT) (capital city of the province of Kocaeli), Adapazari (SKR) (capital of the province of Sakarya), Duzce (DZC) (shaken strongly in both the events), and Bolu (BOL). In many of these urban centers, extensive structural damage was observed. Although these near-field data have greatly expanded the strike-slip near-source ground-motion database worldwide for M-w > 7 earthquakes, they represent a blurred image of the actual severity of the ground motions in the epicentral area because of the sparseness of the national strong-motion network and the unrepresentative geologic conditions at the recording sites. We examine the records to determine whether they provide clues about the extensive damage on the housing stock in the epicentral region. The goal is tackled with earthquake structural engineering criteria in mind, using the drift spectrum as the primary yardstick. There appears to be conflicting evidence that the fault-normal (FN) direction should represent a greater damage-causing potential when this potential is based on ground-story drift spectra. The component with larger ground velocity does correlate better with the component with larger drift demand, but this does not always coincide with the FN direction. The period of the peak velocity pulse matches the structural period where the drift demand is the largest. Further refinements of code requirements that consider this effect are in order.


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Two major earthquakes occurred in Turkey along the North Anatolian fault in 1999. The first one, which occurred on 17 August 1999, had a moment magnitude of 7.4 and ruptured the 140-km segment of the fault in the Marmara region. Adapazari, a city with a population of 190,000, which is mostly located on a deep alluvial basin in the near field of the ruptured fault, was among the worst-affected urban areas in the earthquake-affected region. The distribution of damage over the city was highly nonuniform, indic...
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We studied the source processes of two large continental earthquakes, the 3 November 2002 Denali fault earthquake and the 14 November 2001 Kunlun fault earthquake, associated with strike-slip faulting along ancient sutures. We inverted teleseismic P waveforms using a pulse-stripping method for multiple time windows with different focal mechanisms and derived composite source models. According to our results, the 2002 Denali fault earthquake began with initial thrusting (M-W 7.3) along a 40-km-long segment o...
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Fraser, Jeff; Pigati, J. S.; Hubert-Ferrari, Aurelia; Vanneste, Krıs; Avşar, Ulaş; Altinok, S. (Seismological Society of America (SSA), 2009-10-01)
The North Anatolian fault (NAF) is a similar to 1500 km long, arcuate, dextral strike-slip fault zone in northern Turkey that extends from the Karliova triple junction to the Aegean Sea. East of Bolu, the fault zone exhibits evidence of a sequence of large (M-w > 7) earthquakes that occurred during the twentieth century that displayed a migrating earthquake sequence from east to west. Prolonged human occupation in this region provides an extensive, but not exhaustive, historical record of large earthquakes ...
The 20th July 2017 Bodrum-Kos Tsunami Field Survey
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The July 20, 2017 Bodrum-Kos Earthquake caused tsunami wave motions and damage in the south of Bodrum Peninsula, Turkey, and on Kos Island, Greece. Immediately after the earthquake, we conducted several post-tsunami field surveys including interviews in coastal zones impacted by the tsunami, i.e., the coastlines of Bodrum Peninsula, Karaada Islet and Akyaka Town in Gokova Bay, Turkey, and eastern Kos Island, Greece. We present observations and measurements to document the variation of the tsunami effects al...
The Chios, Greece Earthquake of 23 July 1949: Seismological Reassessment and Tsunami Investigations
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We present a modern seismological reassessment of the Chios earthquake of 23 July 1949, one of the largest in the Central Aegean Sea. We relocate the event to the basin separating Chios and Lesvos, and confirm a normal faulting mechanism generally comparable to that of the recent Lesvos earthquake located at the Northern end of that basin. The seismic moment obtained from mantle surface waves, M-0=7x10(26) dyn cm, makes it second only to the 1956 Amorgos earthquake. We compile all available macroseismic dat...
Citation Formats
S. Akkar and P. Gulkan, “A critical examination of near-field accelerograms from the sea of Marmara region earthquakes,” BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA, pp. 428–447, 2002, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/65016.