![On November 14, 2016, a large magnitude [Mw] 7.8 earthquake
struck the northeastern part of the south island of New Zealand.
• more than 20 mapped faults
• caused widespread crustal deformation
• more than 10,000 landslides in the complex topography of the affected
area
"MOST COMPLEX EARTHQUAKE EVER STUDIED”
(Jibson et al. 2018)](https://image.slidesharecdn.com/monitoringsurfacedeformationcombiningopticalandradarsentineldatagsg2019-190826171753/85/Monitoring-surface-deformation-combining-optical-and-radar-sentinel-data-gsg-2019-2-320.jpg)
Monitoring surface deformation combining optical and radar sentinel data gsg 2019
- 1. Monitoring surface deformation combining Optical and Radar Sentinel data: C.A.Tourlakidis, E.Kalamatianou-Dimitropoulou, P. Krassakis, I. Gougoustamos, A.Fylaktos I. Parcharidis The New Zealand case
- 2. On November 14, 2016, a large magnitude [Mw] 7.8 earthquake struck the northeastern part of the south island of New Zealand. • more than 20 mapped faults • caused widespread crustal deformation • more than 10,000 landslides in the complex topography of the affected area "MOST COMPLEX EARTHQUAKE EVER STUDIED” (Jibson et al. 2018)
- 3. MOTIVATION • Ground deformation caused by earthquakes is a common phenomenon affecting human activities resulting hazards in building stock and infrastructure. • The ring of fire is known to generate seismic activities frequently because of its many convergent boundaries (Plate-inward-sliding). • Earth Observation techniques are quite common tools in order to monitor surface deformation in the last decades.
- 4. AIM • Why? Very complex earthquake • Where? New Zealand-Plate kinematics • Consequence? Hazardous ground deformation and earthquake-triggered landslides • Hypothesis? Combining different Earth Observation techniques and data enhance our results Monitor ground deformation in complex case studies:
- 5. Since 90’s differential repeat-pass interferometry radar (DInSAR) based on SAR images processing has proven an interesting tool for the measurement and observation of ground deformation (Massonnet and Rabaute., 1993). Significant difficulties are found when using this technique. These difficulties are related to: • large variability of slope instabilities, • failure geometries, • size of unstable areas • phase ambiguity • signal decorrelation. EARTH OBSERVATION
- 6. The rocks of New Zealand can be grouped into four elements which correspond to specific tectonic cycles in the geological record: • Western Province (Paleozoic) • Eastern Province (Paleozoic to Cretaceous) • Younger sedimentary and volcanic cover rocks (Cretaceous to Cenozoic). • The oldest rocks in New Zealand are Cambrian (they occur only along the western margin of the South Island). Most of the basement in New Zealand is Mesozoic greywacke, and occurs as schistose metagreywacke (Haast Schist) in large parts of the South Island New Zealand. Also has an unusually thick and complete section of Cenozoic rocks, most of which are marine sedimentary rocks, including limestone, siltstone, and sandstone. GEOLOGY
- 7. GEODYNAMICS It’s location is on the boundary between the Pacific and Indian-Australian plates Subduction zones: • Beneath the North Island, Pacific plate moves down beneath the Australian plate causing volcano activity • South of New Zealand the Australian plate is forced below the Pacific plate Within the South Island the plate margin is marked by the Alpine Fault and here the plates rub past each other horizontally Its dynamic geological past has endowed New Zealand with spectacular scenery and a wide variety of natural resources
- 8. LANDSLIDES The majority of the triggered landslides were shallow- to moderate-depth (1–10 meters), highly disrupted falls and slides in rock and debris from Lower Cretaceous graywacke sandstone in the Seaward Kaikoura Range. Deeper, more coherent landslides in weak Upper Cretaceous to Neogene sedimentary rock also were numerous in the gentler topography south and inland (west) of the Seaward Kaikoura Range. Except from landslides also surface ruptures, seabed rising up to 1,5 meter. The main scarp and upper part of the Sea Front landslide
- 9. The landslide inventory for the 14 November 2016 Mw7.8 Kaikoura earthquake as at 19 May 2017.The active fault ruptures caused by the earthquake are shown as red lines (Dellow et al. 2017). Dellow, S., Massey, C.I., McColl, S.T., Townsend, D.B., Villeneuve, M. (2017) Landslides caused by the 14 November 2016 Kaikoura earthquake, South Island, New Zealand Proc. 20th NZGS Geotechnical Symposium.
- 10. Two main tools based on earth observation data are used to estimate ground surface movements both using SAR products. • DInSAR (Differential Interferometry) based on phase and amplitude of SAR SLC scenes and • Offset tracking (OT) using amplitude-based method GRD in the case of Sentinel images. METHODS
- 11. DATA Master Image Slave Image: November 3rd 2016 December 3rd 2016 Master Image Slave Image: November 3rd 2016 December 3rd 2016 Offset tracking: 2 GRD images of Ascending acquisition For DInSAR: 2 SLC images of Ascending acquisition
- 12. A. DInSAR (Differential Inteferomeromentry SAR) Interferometric SAR (InSAR) exploits the phase difference between two complex radar SAR observations of the same area, taken from slightly different sensor positions, and extracts distance information about the Earth's terrain. If the phase shift related to topography is removed from the interferograms, the difference between the resulting products will show surface deformation patterns occurred between the two acquisition dates. DATA-METHOD S1-SLC: 3 November 2016 & 3 December 2016
- 13. B. Offset tracking The OT is a method to estimate the movements on earth surface using two SAR images (master and slave) in both slant range and azimuth direction .The method is based on cross-correlation on a preselected high number of GCPs (Ground Control Points) in the two scenes after their coregistration. OT is capable of tracking movement rates from tens of centimeters to tens of meters. S1-GRD: 3 November 2016 & 3 December 2016 DATA-METHOD
- 14. Displacement Map generated in SARPROZ*, showing LOS displacement. Data used: 2 SLC Sentinel 1A&B C-band IW Sub-swath: 2 Master date: November 3rd 2016 Slave date: December 3rd 2016 *SARPROZ developed by Dr. D. Perissin, Purdue University, West Lafayette, USA
- 15. Max displacement map using OT (Offset Tracking) Data used: 2 GRD Sentinel 1A&B images C-band IW Sub-swath: 2 Area deformed more than 10m in EW-NS directions
- 16. Displacement map using OT (Offset Tracking) and DInSAR (Differential Interferogram) Data used: 2 SLC & 2 GRD Sentinel 1A&B images C-band IW Sub-swath: 2
- 17. Displacement map using OT (Offset Tracking) and DInSAR (Differential Interferogram) Data used: 2 SLC & 2 GRD Sentinel 1A&B images C-band IW Sub-swath: 2
- 18. CONCLUSIONS • An attempt was done to use optical data, but the results were poor • The products were synthesized, although represent different results • DInSAR show LOS movement – OT show EW-NS results • We can make safe conclusions by combining SAR data analysis with our knowledge about the area’s kinematics • Further research can be done, combining DInSAR & OT providing results in common scale. Thank you