psi ground motion in northumberland and durham, uk · 2021. 5. 25. · northumberland: psi data...
TRANSCRIPT
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Terrafirma: a Pan-European Terrain motion hazard information service
www.terrafirma.eu.com
PSI Ground Motion in Northumberland and Durham, UK
Luke Bateson and David Lawrence, BGS.
Harry McCormack and Richard Burren, FNPA.
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Terrafirma: A Pan-European Terrain Motion Hazard Information Service
Outline
• Introduction to the area of interest
• The PS data used in the study
• Interpretation case studies – ERS PSI
• Difference between ERS and Envisat PSI
• Interpretation of Envisat motions
• Conclusions
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Terrafirma: A Pan-European Terrain Motion Hazard Information Service
Introduction to the area of interest – Location
• Long history of coal mining
• Dating back to Roman times
• Last active mine closed in 2005
• 20+ coal seams mined underground
• Extensive opencast mining
• Working of deeper coal led to the need to pump mine water
• Recent years – reduction in pumping and recovery of mine water levels
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Terrafirma: A Pan-European Terrain Motion Hazard Information Service
Introduction to the area of interest – Bedrock Geology
• Oldest Strata; Stainmore formation in NW
• Youngest Strata; Zechestein Group in SE
• Coal measures; Mudstones, Ironstones, Sandstones and Coal
• Coal measures dip to the east (<10°)
• Faults within the Coal Measures
• Typical displacements 25 m or less
• can be up to 170m
1:625 000 Scale 1:50 000 Scale
Northern England thloeiitic Dyke-swarm
Mull Dyke-swarm
Roker Formation
Ford Formation - Reef
Ford Formation
Seaham Formation
Yellow Sand Formation
Pennine Upper Coal Measures
Sandstone in Pennine Upper Coal Measures
Pennine Middle Coal Measures
Sandstone in Pennine Middle Coal Measures
Pennine Lower Coal Measures
Stainmore Formation
Igneous rocks
Sedimentary rocks
Carboniferous
Permian
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Terrafirma: A Pan-European Terrain Motion Hazard Information Service
Northumberland: PSI data used in the study
• Processed by FugroNPA Ltd
• ERS descending PSI data (1995 – 2000)
• 50 ERS scenes
• 19 April 1995 to 14th December 2000
• 115 555PS points identified
• Overall average annual motion of +0.407mm/yr
• ENVISAT descending PSI data (2002 – 2008)
• 21 ENVISAT scenes
• 3rd December 2002 to the 7th October 2008
• 71899 PS points identified
• Overall average annual motion rate of +2.47mm/yr
• ERS Ascending DifSAR data (1992 – 2000)
• ENVISAT Ascending DifSAR data (2002 – 2009)
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Terrafirma: A Pan-European Terrain Motion Hazard Information Service
ERS / Envisat PSI Results
ERS descending PSI: 1995 - 2000
Envisat descending PSI: 2002 - 2008
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MOTION RELATING TO FAULTING
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Terrafirma: A Pan-European Terrain Motion Hazard Information Service
Comparison of ERS PSI with major faults
• Motion appears to be constrained by the faulting
• Faults are accommodating motion caused by another factor.
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Terrafirma: A Pan-European Terrain Motion Hazard Information Service
Comparison of Envisat PSI with major faults
• Envisat motion and major faults
• Fewer areas of motion now appear to be constrained by the faulting
• A more regional explanation for the uplift to the south of Newcastle?
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TEAM VALLEY
Case Study…….Compressible sediments
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Terrafirma: A Pan-European Terrain Motion Hazard Information Service
Compressible sediments in the Team Valley
ERS 1995 – 2000 Building weight causes
compression
ENVISAT 2002 – 2008 Influx of water causes uplift?
Cyclical shrink
swell trend?
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Terrafirma: A Pan-European Terrain Motion Hazard Information Service
Compressible sediments in the Team Valley
ERS 1995 – 2000Building weight causes
compression
• Deep in-filled valley• Loading of ground• Sealing of ground• Possible pumping• Lead to ‘drying out’ of sediments
A A
A
B
B
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HOUGHTON-LE-SPRING
ERS Motion - Case Study……..Mining related subsidence or water abstraction?
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Terrafirma: A Pan-European Terrain Motion Hazard Information Service
Houghton-Le-Spring
• Complex subsidence pattern shown in the ERS data
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Terrafirma: A Pan-European Terrain Motion Hazard Information Service
Houghton-Le-Spring
• Field observations of cavities and fissures in Houghton-le-Spring (purple stars and red lines)
• PSI shows differential motion across fault
• Field observations show fissures and cavities opening due to motion associated with the fault
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Terrafirma: A Pan-European Terrain Motion Hazard Information Service
Northumberland: Value added product results
Houghton-Le-Spring
• Mine abandonment plans:
• area worked until 1981,
• mining was pillar and stall
• areas of underground water
• Did a combination of
these lead to motion,
which was accommodated
by the faults?
Approximate line of fissures on previous slide
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SITES OF ABANDONED MINING
Case Studies
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Terrafirma: A Pan-European Terrain Motion Hazard Information Service
Ryhope Colliery (ERS 95-2000) – Non-linear subsidence
1859 - 1966
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Envisat PSI Motions
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Terrafirma: A Pan-European Terrain Motion Hazard Information Service
Northumberland: Overall change between processing periods
ERS 1995-2000
• Differences confirmed by DifSAR and separate PSI and SBAS studies
• Overall change
• Most subsiding areas in 95-00 are uplifting in 02-08
• Dramatic change mainly related to mine water pumping regimes
ENVISAT 2002-2008
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Terrafirma: A Pan-European Terrain Motion Hazard Information Service
Northumberland: Overall change between processing periods
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Terrafirma: A Pan-European Terrain Motion Hazard Information Service
Mine Water Recovery - Envisat
Westoe minewater
monitoring point
Boldon
minewater
monitoring
point
Wearmouth
minewater
monitoring point
Minewater recovery
blocks
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Terrafirma: A Pan-European Terrain Motion Hazard Information Service
Conclusions
• PSI ground motion is related to:
• Thickness of superficial deposits
• Fault locations
• Ground water pumping and minewater recovery
• Spatial association to abandoned mines – but no temporal association
• Envisat PSI does not detect small scale motions related to pillar collapse
• but no PSI directly over the area of motion and slight discrepancy in dates
• Subsidence seen in ERS data is likely to be a result of the complex relationship between
1. pumping of the ground water to prevent flooding of mine workings
2. general groundwater abstraction
3. accommodation of motion by the faults, fissures and joints in the area.