active faults in korea - tohoku university official...
TRANSCRIPT
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Choi, Jin-HyuckActive Tectonics Research Team, KIGAM
email: [email protected]: https://sites.google.com/site/jinhyuckchoi9521/
Active faults in Korea: recent research & current trends
Collaboration withKim, Y.-S. et al (Korean Active Fault Research Group)Lee, S.-R. et al (KIGAM project_17-3112)
CCOP-IUGS Task Group on Geohazards (TGG) Joint Seminar 30 Oct. 2018
MW 5.5 GJ eq. (Sep. 2016)
MW 5.4 PH eq. (Nov. 2017)
We are here
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(updated from Roger Bilham, 2009)
Large earthquakes cause destructive disaster
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1906 Mw 7.8 San Francisco eq. along the San Andreas fault
Earthquake rupture for all individual events
Earthquake ‘surface’ rupture for seismic events larger than MW 5.5
(Single-fault magnitude frequency relation) (Down-dip rupture width of earthquakes)
Surface records of large earthquakes
(Zielke & Arrowsmith, 2008)
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Plate tectonic setting & Crustal deformation
- No large (M ≥ 5.5) earthquake in South Korea (1900 - early 2016)
- Unobservable crustal (fault) deformation (except for the 2011 Tohoku-Oki ep.)
(USGS) (Absolute velocities before(red) and after(blue) the 2011 Tohoku-Oki eq.: Kim et al.., 2015)
We are here
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Historical & Instrumental seismicity
(KMA)
MMI > V (2-1904) 2 ≤ M ≤ 5.5 (1978-2017)
- 15 large historical earthquakes (the estimated magnitude: 6.5 < ML < 6.9)
- 10 moderate-sized (5 ≤ M ≤ 5.5) instrumental earthquakes
2017 Mw 5.42016 Mw 5.5
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Active faults - Large (M ≥ 5.5) earthquakes during the Quaternary
Wangsan Fault(from Choi, W.-H.’s presentation)
YSD
YSDUC
UC
Andesite
Andesite
- Stratigraphic records data at ~ 100 sites
- No published active fault map
- Long recurrence interval of large eqs.
- We are living in long inter-seismic period
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No surface rupture
ALOS-2 PALSAR images(21/07/2015 & 13/09/2016)
The 2016 MW 5.5 Gyeongju earthquake
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(Elliott et al., 2016) (Kim et al., 2017)Next slide
Flow diagram of post-earthquake research No surface rupture, but aftershock sequence
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(Kim et al., 2017)
Earthquake rupture on a subsidiary fault in western damage zone of the Yangsan Fault
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(Central Geological Survey, Taiwan)
- Active fault map for the entire area of S. Korea
(KAFRG, 2017-2036)
- Strip map of the Central Yangsan Fault
(the epicenter area of the 2016 Gyeongju eq.)
(KIGAM, 2017-2019)
Active faults project (after the 2016 MW 5.5 Gyeongju eq.)
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Development of investigation and evaluation technology for active faults in Korea
Private Advisory Board National Institute for Disaster Prevention
Main research institutePKNU
• Standardization
• Topographic analysis
• Structure analysis
• Paleoseismological
analysis
Joint research instituteKIGAM
Joint research instituteKBSI
Joint research institutePNU
Ministry of the Interior and Safety
• Topographic analysis
• Structure analysis
• Paleoseismological
analysis
• Topographic analysis
• Structure analysis
• Paleoseismological
analysis
• Development of
analysis protocol
• Dating
• Dating data verification
Committedresearch institutionChung-Ang Aero Survey
• Imaging LiDAR image
Committed research institutionSaehan Aero Survey
• Imaging LiDAR image
KAFRG (Korean Active Fault Research Group, 2017-2036)
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(Haddad et al., 2012)(Howle et al., 2012)
Airborne LiDAR
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Active faults project - The southern sections of the Yangsan Fault (YSF)
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100 m
- Wallace Creek along the San Andreas Fault
(Sieh and Jahns, 1984; Sieh and Wallace, 1987)
Abandoned channel
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Smaller horizontal displacement
along the central (?) Yangsan Fault
- Younger geomorphic marker ? - Lower slip-rate ? - Longer recurrence time ?- More distributed deformation ?
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Fault Segmentation
(Wesnousky, 2006)
(Mignan et al., 2015)
- Earthquake rupture propagation is directly affected by the fault geometry and discontinuities
- Fault segmentation is an essential factor to define earthquake cycle models
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Segmentation of the Yangsan Fault
Along-fault variations in geologic inheritance, geomorphic features, fault geometry, and seismic patterns
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The 2017 MW 5.4 Pohang earthquake
No surface rupture, but second-order surface deformations (Choi et al., in press)
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(Lee et al., 2014)(Choi et al., in press)
Surface evidence of paleo-earthquakes
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Summary
- Recent two moderate-sized earthquakes occurred in the
southeastern part of the Korean Peninsula.
- There have been multiple large (M ≥ 5.5) earthquakes along
the Yangsan Fault and on its eastern block, and there are
neotectonically active crustal structures in this region.
- Geomorphic expression of the fault, which is observable in
high-resolution topographic data, plays a key role in the study
of paleo-earthquakes.
- It is needed to date more offset geomorphic markers (slip-rate)
and to excavate ‘young’ but ‘old’ stratigraphic records (temporal
history).