Abstract
We reevaluate the 72 year history of surface slip on the North Anatolian Fault at Ismetpasa since the Mw = 7.4 1944 Bolu/Gerede earthquake. A revised analysis of published observations suggests that days after the earthquake the fault had been offset by 3.7 m and 6 years later by an additional 0.74 m. Creep was first recognized on the fault in 1969 as a 0.13 m offset of a wall constructed in 1957 that now (2016) has been offset by 0.52 m. A carbon rod creep meter operated across the fault in the past 2 years confirms results from an invar wire creep meter operated 1982–1991 that surface slip is episodic. Months of fault inactivity are interrupted by slow slip (≤10 µm/d) or multiple creep events with cumulative amplitudes of 2–10 mm, durations of several weeks, and with slip rates briefly exceeding >2.5 mm/h. Creep events accommodate 80% of the surface slip and individually release ≈ 10−6 shear strain on the flanks of the uppermost 3–7 km of the fault. GPS and interferometric synthetic aperture radar methods yield a current fault slip rate of 7.6 ± 1 mm/yr suggesting that creep meters incompletely sample the full width of the surface shear zone. The slip rate has slowed from >10 mm/yr in 1969 to 6.1 mm/yr at present, 4.65 mm/yr of which appears to be due to steady interseismic creep driven by plate boundary stressing rates. We calculate that a further 1 m of aseismic surface slip will precede the next major earthquake on the fault assuming an ≈ 260 year main shock recurrence interval on this segment.
Original language | English |
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Pages (from-to) | 7409-7431 |
Number of pages | 23 |
Journal | Journal of Geophysical Research: Solid Earth |
Volume | 121 |
Issue number | 10 |
DOIs | |
Publication status | Published - 1 Oct 2016 |
Bibliographical note
Publisher Copyright:©2016. The Authors.
Funding
The project was funded by NSF grants EAR 1349851/1622720 and by Scientific Research Projects of Bogazici University under grant 10240. We thank Clarence Allen, James Jackson, and Wayne Thatcher for providing us with their original photographs of the wall at Ismetpasa and Frank Wyatt for providing us with a measure of the pen length in the Rustrak recorders with which we corrected nonlinearity in the 1987 chart records. The manuscript has been substantially improved following thoughtful reviews by Jim Lienkaemper, Sylvain Barbot, the Associate Editor, and an anonymous reviewer. We acknowledge the importance of independent evaluation of the Ismetpasa data, and the supporting information provide copies of the photographs used in our analysis and digital listings of the 1982–1991 and 2014–2016 creep meter data.
Funders | Funder number |
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Clarence Allen | |
James Jackson | |
Scientific Research Projects of Bogazici University | 10240 |
National Science Foundation | EAR 1349851/1622720 |
Keywords
- 1944 Bolu earthquake
- afterslip
- creep meter
- fault creep
- North Anatolian Fault