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Developments on the EPOS-IP strain rate productAthanassios Ganas, NOA, Greece, [email protected] Kapetanidis, NOA-NKUA, GreeceFaramarz Nilfouroushan, LM, Gävle, Sweden, University of Gävle, SwedenHolger Steffen, LM, Gävle, Sweden, University of Gävle, SwedenMartin Lidberg, LM, Gävle, SwedenAline Deprez, CNRS-UGA, Grenoble, FranceAnne Socquet, CNRS-UGA, Grenoble, FranceAndrea Walpersdorf, CNRS-UGA, Grenoble, FranceAntonio Avallone, INGV, Rome, ItalyNicola D’ Agostino, INGV, Rome, ItalyJuliette Legrand, ROB, Brussels, BelgiumCarine Bruyninx, ROB, Brussels, BelgiumEduard Nastase, INCDFP RA, Bucharest, Romania,Constatin Ionescu, INCDFP RA, Bucharest, Romania,Ambrus Kenyeres, BFKH, Budapest, Hungary,Tomasz Liwosz, WUT, Warsaw, Poland, Wolfgang Soehne, BKG, Frankfurt-am-Main, GermanyMachiel Bos, UBI/C4G, Covilhã, PortugalRui Fernandes, UBI/C4G, Covilhã, Portugal
European Seismological Commission
36th General Assembly, 2-7 September 2018, Valletta - Malta
ESC2018 - S2 - 749
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OUTLINE of PRESENTATION
1. Strain rates are of great importance for Solid Earth Sciences. Within the EUHorizon 2020 project EPOS-IP WP10 TCS-GNSS (Global Navigation SatelliteSystem - GNSS thematic core services) a series of products focused on strainrates derived from GNSS data is envisaged.
2. In this contribution, we present preliminary results from 452 permanentEuropean GNSS stations, operating until 2017 and processed at UGA-CNRS(Université Grenoble Alpes, Centre National de la Recherche Scientifique).
3. We calculated the strain-rate field using two open-source algorithmsrecommended by EPOS-IP, namely the VISR (Velocity Interpolation for StrainRate) algorithm (Shen et al., 2015) and STIB (Strain Tensor from Inversion ofBaselines), developed by Masson et al., (2014) as well as the SSPX softwaresuite (Cardozo and Allmendinger, 2009).
4. We compared the results derived from different methods and discuss thesimilarities and differences.
5. We also validated our results w.r.t literature.
European Seismological Commission
36th General Assembly, 2-7 September 2018, Valletta - Malta
ESC2018 - S2 - 749
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1. GNSS velocity data
EPOS Velocity data (452 permanent stations with data spanning more
than 3 years)
Processed with DD for positions operating until 2017 by UGA-CNRS,
with MIDAS (UNR) for velocities
Italy grid LON/LAT: 4.5°E<=lon<=20°E , 35°N<=lat<=48.5°N) 213 stations
Greece grid LON/LAT: 19.5°E<=lon<=29°E , 34°N<=lat<=42°N) 20 stations
Note
The first product is focused on Italy and Greece because of a) magnitude of
strain-rate w.r.t rest of Eurasia and b) availability of stations
European Seismological Commission
36th General Assembly, 2-7 September 2018, Valletta - Malta
ESC2018 - S2 - 749
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GNSS data (left) GNSS stations (red triangles) in Europe, (right) GNSS velocities (ITRF08 frame) in the CNRS MIDAS data
GNSS Stations Map: Italy (+Alps, Dinarides)
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(left) GNSS stations (red triangles) in Italy, (right) GNSS velocities in the CNRS MIDAS data
European Seismological Commission
36th General Assembly, 2-7 September 2018, Valletta - Malta
ESC2018 - S2 - 749
GNSS Stations Map: Greece
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(left) GNSS stations (red triangles) in Greece, (right) GNSS velocities in the CNRS MIDAS data
European Seismological Commission
36th General Assembly, 2-7 September 2018, Valletta - Malta
ESC2018 - S2 - 749
7
Model Configuration:
spatial smoothing
Min 1 km
Max 500 km
Incr. 1 km
Dist. Weight: Gaussian
Spat. Weight: Voronoi
Weight 6
Unc Thresh 0.5
Grid step 0.5°
2a. VISR result: strain-rates in Greece
Compression domains (Ionian Sea, N. Aegean Sea) are mapped satisfactorilyCompression enters into central Greece which is not justified by seismology/geologyextension in central Greece is correct in azimuth but underestimated in magnitudeEast-west switch is not well resolved
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Model Configuration:
spatial smoothing
Min. 100 km
Max. 500 km
Incr. 30 km
Dist. Weight Gaussian
Spat. Weight Voronoi
Weight 6
Unc. Thresh 0.5
Grid step 0.5°
VISR result: strain-rates in Italy
strain orientation seems correctstrain character seems correctstrain magnitude underestimated
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Model Configuration: spatial smoothing Min 100 km Max 500 km Incr 30 km Dist Weight
Gaussian Spat Weight Voronoi Unc Thresh 0.5 Grid step 0.5°
VISR result: strain-rates in Italy – influence of Wt increase
Left Wt=12, middle Wt=24, right Wt=48
European Seismological Commission
36th General Assembly, 2-7 September 2018, Valletta - Malta
ESC2018 - S2 - 749
increase of Wt = smoother strain field, compression in the Po valley vanishes
2b. STIB: main processing parameters
Grid configurations
Smoothing Distance (e.g. 10km, 30km, 50km, 200km etc.)
Europe Min Max Step
Longitude -12.5 44.2 2.0
Latitude 26.7 72.6 2.0
Italy Min Max Step
Longitude 4.5 20.0 0.5
Latitude 35.0 48.5 0.5
Greece Min Max Step
Longitude 19.5 29.0 0.5
Latitude 34.0 42.0 0.5
10European Seismological Commission
36th General Assembly, 2-7 September 2018, Valletta - Malta
ESC2018 - S2 - 749
The STIB approach uses the length variations of the baselines between each pair of the geodetic stations to provide a map of the deformation over the whole area covered by the network, reducing the impact of erroneous data and noise. The computation of the strain rate tensor is obtained by inversion of the variation of the length of all the baselines obtained from the geodetic network.
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STIB result: principal strain-rate axes in Greece – grid step of 0.5°.
Left ) smoothing distance 50 km Right ) smoothing distance 100 km
Compression domains (Ionian Sea, N. Aegean Sea) are mapped satisfactorilyorientation of extension in central Greece deviated by 20-40 degreespicked up 90 degrees switch in extension along mainland Greece
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STIB result: principal strain-rate axes in Italy - grid step of 0.5°.
Left) smoothing distance 30 km Right ) smoothing distance 50 km
Extension resolved across the Apennines - compression in the Po valley, Dinaridesstrain magnitude reasonable ~50 ns/yr Apenninesno significant differences between 30-50 km smoothing distance
SSPX: main processing parameters
Grid configurations
Europe Min Max Step
Longitude -12.5 44.2 2.0
Latitude 26.7 72.6 2.0
Italy Min Max Step
Longitude 4.5 20.0 0.5
Latitude 35.0 48.5 0.5
Greece Min Max Step
Longitude 19.5 29.0 0.5
Latitude 34.0 42.0 0.5
13European Seismological Commission
36th General Assembly, 2-7 September 2018, Valletta - Malta
ESC2018 - S2 - 749
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SSPX result: principal strain-rate axes in Greece Italy - grid step 43 km.
Comparison of VISR-SSPX results for Italy (common nodes = 733)
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Product: Dilatation_Italy (VISR original – VISR interpolated at SSPX nodes – SSPX)
GNSS stations are shown as yellow triangles
European Seismological Commission
36th General Assembly, 2-7 September 2018, Valletta - Malta
ESC2018 - S2 - 749
Statistical Comparison of results for Italy (common nodes = 733)VISR parameters are Wt=12, smoothing distances 1-200km
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Diagonal lines indicate 1:1 fit
European Seismological Commission
36th General Assembly, 2-7 September 2018, Valletta - Malta
ESC2018 - S2 - 749
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3a. Product Validation - Greece
Chousianitis Ganas Evangelidis (2015) result: strain-rate in mainland Greece
Floyd et al. (2010) result: principal strain-rate axes in broader Aegean
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3b. Product Validation - Italy
Figure 11 D'Agostino (2014) result: principal strain-rate axes in Italy
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3b. Product Validation - Italy
1. A good match exists between the EPOS product and the Quaternary faults which are accommodating the extension in the Calabrian Arc (Calabria + NE Sicily)
2. We have also highlighted where compression is mapped.
3. This compression is the result of the Eurasia and Africa collision and it is "shared" between the SBT and the thrust fault system offshore north of Sicily.
20Principal axes of strain plotted using gmtstrainplot.sh script. Yellow circles
show EPOS GNSS sites with their codes
https://github.com/DSOlab/StrainTool .
DOI: 10.5281/zenodo.1297565
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4. Summary of Preliminary results
1. We presented preliminary results from 452 permanent EuropeanGNSS stations, operating until 2017 and processed at UGA-CNRS withDD technique.
2. We calculated the strain-rate field using two open-source algorithmsrecommended by EPOS-IP, namely the VISR and STIB as well as theSSPX software suite.
3. Overall, our first results reproduce the gross features of tectonicdeformation in both Italy and Greece, such as NE-SW extension acrossthe Apennines and N-S extension in Central Greece.
4. It is anticipated that the significant increase of GNSS data amountassociated with the operational phase of EPOS in the forthcomingyears will be of great value to perform an unprecedented, reliablestrain rate computation over the Eurasian plate.
European Seismological Commission
36th General Assembly, 2-7 September 2018, Valletta - Malta
ESC2018 - S2 - 749
22European Seismological Commission
36th General Assembly, 2-7 September 2018, Valletta - Malta
ESC2018 - S2 - 749
Thanks!