Pyroclastic density currents - PowerPoint Presentation

1. Pyroclastic density currents and tephra fallout hazard assessment at Tungurahua volcano, Ecuador: hazard maps with uncertainty quantificationAlessandro TadiniAlvaro Aravena, Andrea Bevilacqua, Pablo Samaniego, Benjamin Bernard, Silvana Hidalgo, Nourddine Azzaoui, Olivier RocheHeraklion, 13/06/2022

2. Presentation outlineIntroductionTungurahua volcanoNumerical modellingTephra fallout (TF)Pyroclastic Density Currents (PDC)Uncertainty quantification procedureHazard mapsConclusions and perspectives2Tadini et al.PDC and TF hazard maps at Tungurahua with UQ1 - Introduction2 – Numerical modellingTephra fallout and PDC3 – UncertaintyQuantification4 – Hazard maps5 – Conclusions and perspectives

3. 3Tadini et al.PDC and TF hazard maps at Tungurahua with UQ1 - Introduction2 – Numerical modellingTephra fallout and PDC3 – UncertaintyQuantification4 – Hazard maps5 – Conclusions and perspectives1) From field dataIntroduction: hazard mapsMothes et al., 2016COTOPAXIRelatively strightforwardBUTPotentially large epistemic uncertainty (under-recording of small events)2) Numerical modelsDeterministic (scenario-related with fixed ESP)Semi- or fully probabilisticInput parametersNumerical modelProbability of occurrence of eruptive scenariosMain sources of uncertaintyBiass et al., 2014Neri et al., 2015Partial hazard assessmentSingle/multiple scenarios with ESP sampling

4. Tungurahua volcano4Tadini et al.PDC and TF hazard maps at Tungurahua with UQ1 - Introduction2 – Numerical modellingTephra fallout and PDC3 – UncertaintyQuantification4 – Hazard maps5 – Conclusions and perspectivesBustillos et al., 2016Ash emissionLast eruptive cycle (1999-2016)Vulcanian to StrombolianSub-Plinian (up to VEI 3)Samaniego et al., 2008PDC and TF hazard mapMean annual wind direction/velocitiesTungurahuaVEI 3 (August 2006) hazard mapBased on field data3 mm30 mmHigher PDC hazardLower PDC hazard

5. 5Tadini et al.PDC and TF hazard maps at Tungurahua with UQ1 - Introduction2 – Numerical modellingTephra fallout and PDC3 – UncertaintyQuantification4 – Hazard maps5 – Conclusions and perspectivesTungurahua volcano: hazard maps developmentTephra falloutPyroclastic Density CurrentsMaps conditioned on the occurrence of a Sub-Plinian (VEI 3-4) eventESP sampling(MFR/Duration)PLUME-MoM/HYSPLIT(x 1200 simulations)Correction coefficientsSet of hazard mapsSet of hazard curvesMeteo data sampling(last 15 years)Set of hazard mapsInundation area of reference PDCECMapProb calibration simulations (400)BoxMapProb calibration simulations (400)Inputs definition based on different metrics (3 sets)Inputs definition based on different metrics (3x3 sets)CalibratedSimulations(12 x 1000)

6. Numerical models: Tephra dispersal/fall6Tadini et al.PDC and TF hazard maps at Tungurahua with UQ1 - Introduction2 – Numerical modellingTephra fallout and PDC3 – UncertaintyQuantification4 – Hazard maps5 – Conclusions and perspectivesPLUME-MoMHYSPLITInput: duration/MFR.Output: plume height and mass release at different heights.Umbrella cloud modelling.de’ Michieli Vitturi and Pardini, 2021Stein et al., 2015Input: mass release along the plume (points) and from the umbrella cloud (surface).Output: mass loading (kg/m2) on a grid.Gaussian «puff» configuration.Eulerian integral model for the steady-state dynamics of a plume in a 3-D coordinate system.Mixed Lagrangian (particles/puffs advection) and Eulerian (mass concentration/deposition at fixed receptors) approaches.

7. 7Tadini et al.PDC and TF hazard maps at Tungurahua with UQ1 - Introduction2 – Numerical modellingTephra fallout and PDC3 – UncertaintyQuantification4 – Hazard maps5 – Conclusions and perspectivesNumerical models: PDCECMapProbBoxMapProbInputs: collapse position, root energy cone height, energy cones slope.Output: inundation area.Aravena et al., 2022Aravena et al., 2022Inputs: collapse position, collapsing volume, initial concentration, sedimentation velocity, Froude number, ambient air density, pyroclast density.Output: inundation area.Branching formulation of the energy cone model for the propagation dynamics of PDCs considering channelization processes. Suitable for dominantly frictional PDCs.Branching formulation of the box model for the propagation dynamics of PDCs considering channelization processes. Suitable for dominantly inertial PDCs.

8. 8Tadini et al.PDC and TF hazard maps at Tungurahua with UQ1 - Introduction2 – Numerical modellingTephra fallout and PDC3 – UncertaintyQuantification4 – Hazard maps5 – Conclusions and perspectivesUncertainty quantification: TFCorrection coefficients(Upper/Lower)  Tungurahua 16/08/2006 eruption (sub-Plinian VEI 3)ModeluncertaintySimulationComparisonfield dataESP/meteo frombibliographyMass loading value from bibliographyEychenne et al., 2012Stratigraphic sections with mass loading measurements (kg/m2)

9. 9Tadini et al.PDC and TF hazard maps at Tungurahua with UQ1 - Introduction2 – Numerical modellingTephra fallout and PDC3 – UncertaintyQuantification4 – Hazard maps5 – Conclusions and perspectivesUncertainty quantification: PDCTungurahua August 2006 eruption (sub-Plinian VEI 3)CalibrationsimulationsMap of Tungurahua volcano. Dark area: inundation zone of the 2006 PDCs (Eychenne et al., 2013)Inputs definition andcalibrated simulationsSet of independent hazard maps (model uncertainty)

10. 10Tadini et al.PDC and TF hazard maps at Tungurahua with UQ1 - Introduction2 – Numerical modellingTephra fallout and PDC3 – UncertaintyQuantification4 – Hazard maps5 – Conclusions and perspectivesPreliminary hazard maps and curves: TF1 mm10 mm100 mm3-30 mm10% unc. area50% unc. area90% unc. area10% unc. area (3 mm)10% unc. area (30 mm)3 mm30 mmSamaniego et al. 2008Population affected (10%)1 mm10 mm100 mmLowerUpper~1,500,000~ 400,000-~ 2,000,000~ 1,000,000~ 1,000Exceedance probability of tephra accumulation with a VEI 3-4 event

11. 11Tadini et al.PDC and TF hazard maps at Tungurahua with UQ1 - Introduction2 – Numerical modellingTephra fallout and PDC3 – UncertaintyQuantification4 – Hazard maps5 – Conclusions and perspectivesPreliminary hazard maps: PDCECMapProb (mean value)ECMapProb (max value)BoxMapProb (max value, ws = 0.05 m/s)BoxMapProb (mean value, ws = 0.05 m/s)Probabilistic PDC inundation maps for a VEI 3 sub-Plinian eruption at Tungurahua volcano.

12. 12Tadini et al.PDC and TF hazard maps at Tungurahua with UQ1 - Introduction2 – Numerical modellingTephra fallout and PDC3 – UncertaintyQuantification4 – Hazard maps5 – Conclusions and perspectivesConclusions and future workTephra falloutPyroclastic Density CurrentsUncertainty in hazard maps: communication strategies?Hazard maps/curves with ESP/model UQ for VEI 3-4 eruption type.Significant variability in final results if all uncertainties are considered.Calibrated hazard maps for VEI 3-4 eruption type.Different calibration metrics allow definition of uncertainty ranges.Uncertainty in the nature of future PDCs (frictional vs. inertial) is treated by adopting and coupling two independent models.Replicate such maps for smaller/larger magnitude eruptions (merging?).Replicate such maps for smaller/larger magnitude eruptions (merging?).Refine UQ procedure.

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