Title of article :
shallow fault-zone structure illuminated by trapped waves in the Karadere-Duzce branch of the North Anatolian Fault, western Turkey
Author/Authors :
Ben-Zion، Yehuda نويسنده , , Seeber، Leonardo نويسنده , , Armbruster، John G. نويسنده , , Peng، Zhigang نويسنده , , Michael، Andrew J. نويسنده , , Okaya، David نويسنده , , Ozer، Naside نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2003
Pages :
-698
From page :
699
To page :
0
Abstract :
We discuss the subsurface structure of the Karadere-Duzce branch of the North Anatolian Fault based on analysis of a large seismic data set recorded by a local PASSCAL network in the 6 months following the Mw= 7.4 1999 Izmit earthquake. Seismograms observed at stations located in the immediate vicinity of the rupture zone show motion amplification and longperiod oscillations in both P- and S-wave trains that do not exist in nearby off-fault stations. Examination of thousands of waveforms reveals that these characteristics are commonly generated by events that are well outside the fault zone. The anomalous features in fault-zone seismograms produced by events not necessarily in the fault may be referred to generally as fault-zone-related site effects. The oscillatory shear wave trains after the direct S arrival in these seismograms are analysed as trapped waves propagating in a low-velocity fault-zone layer. The time difference between the S arrival and trapped waves group does not grow systematically with increasing source-receiver separation along the fault. These observations imply that the trapping of seismic energy in the Karadere-Duzce rupture zone is generated by a shallow fault-zone layer. Traveltime analysis and synthetic waveform modelling indicate that the depth of the trapping structure is approximately 3-4 km. The synthetic waveform modelling indicates further that the shallow trapping structure has effective waveguide properties consisting of thickness of the order of 100 m, a velocity decrease relative to the surrounding rock of approximately 50 per cent and an S-wave quality factor of 10-15. The results are supported by large 2-D and 3-D parameter space studies and are compatible with recent analyses of trapped waves in a number of other faults and rupture zones. The inferred shallow trapping structure is likely to be a common structural element of fault zones and may correspond to the top part of a flowertype structure. The motion amplification associated with fault-zone-related site effects increases the seismic shaking hazard near fault-zone structures. The effect may be significant since the volume of sources capable of generating motion amplification in shallow trapping structures is large.
Keywords :
stereochemistry , Triorganylstannyl , Regiochemistry , Alicyclic Aliphatic Substrates , (alpha)Carbon , Cycloalkyl Halides , Oxygen , Aliphatic Substrates , Carbonylation , Sulfur Nucleophiles , Phosphorus Nucleophiles , EWG , Neopentyl , Nitrobenzyl , sp2 Carbons , Cumyl , sp3 Carbons , Heterocyclic Analogues , Radicals Intermediates , Trihalides , Photostimulated Reactions , Geminal Dihalides , Nitrogen Nucleophiles , Carbanions , Nitroalkanes
Journal title :
GEOPHYSICAL JOURNAL INTERNATIONAL
Serial Year :
2003
Journal title :
GEOPHYSICAL JOURNAL INTERNATIONAL
Record number :
71275
Link To Document :
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