V. Pinel, A. Hooper, S. de la Cruz-Reyna, G. Reyes-Davila, M.P. Doin

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Two typical andesitic stratovolcanoes Steep slopes (> 30 ) Highly vegetated 5426 m 3850 m

Caracteristiques des strato-volcans andesitiques Two typical andesitic stratovolcanoes In the past: - Plinian eruptions/pyroclastic flows - Large flank sector collapses

Caracteristiques des strato-volcans andesitiques Current activity of Popocatepetl and Colima Volcano Since 1994 Succession of eruptive cycles - Dome construction - Explosions - Lava or Pyroclastic flows Since 1998

Caracteristiques des strato-volcans andesitiques Current activity of Popocatepetl and Colima Volcano Since Juin 1997 1994 Succession of eruptive cycles - Dome construction - Explosions - Lava or Pyroclastic flows Since Fin 2002 1998

Caracteristiques des strato-volcans andesitiques Current activity of Popocatepetl and Colima Volcano July 2001 Succession of eruptive cycles - Dome construction - Explosions - Lava or Pyroclastic flows Since March 1998 2005

Caracteristiques des strato-volcans andesitiques Current activity of Popocatepetl and Colima Volcano Pyroclastic Since 1994flow of January 2001 Succession of eruptive cycles - Dome construction - Explosions - Lava or Pyroclastic flows Since Lava 1998 flow October 2004

ENVISAT data (ESA Cat 1 project N 3312): (11/2002! 02/2007) B T Descending Track 255 Small activity Small deformation reversible (EDM) B TLAMACAS-CANARIO 0.31 2882 + 0.3 0.29 0.28 0.27 0.26 0.25 20-20- 18-15- Nov- Mar- Jul-01 Nov- 00 01 01 15-13- 10- Mar- Jul-02 Nov- 02 02 10-8-Jul- 5-4- 2-Jul- 30-27- Mar- 03 Nov- Mar- 04 Oct- Feb- 03 03 04 04 05 fecha 27- Jun- 05 25-22- Oct- Feb- 05 06 22- Jun- 06 20- Oct- 06 17- Feb- 07 17- Jun- 07 T Ascending Track 148

ENVISAT data (ESA Cat 1 project N 3312): (12/2002! 08/2006) Effusive activity : sept!nov. 2004 Explosions : march!sept. 2005 Descending Tracks 255 and 384 B B 103W T T Ascending track 48 B B T

805 735 Temporal baseline ( T, days) 595 385 350 175 70 35 59 89 216 409 80 185 388 435 450 526 760 Perpendicular Baseline (B, m)

Method used to improve signal/noise ratio :!Interferograms obtained with DORIS.!Persistent Scatterers : (Hooper et al, 2007) 35500 Optimised for non urban areas. No assumption on the deformation temporal behaviour.

Method used to improve signal/noise ratio :!Interferograms obtained with DORIS.!Persistent Scatterers : (Hooper et al, 2007) Optimised for non urban areas. No assumption on the deformation temporal behaviour.!small Baseline Method: 35500 24500

Method used to improve signal/noise ratio :!Interferograms obtained with DORIS.!Persistent Scatterers : (Hooper et al, 2007) 35500 Optimised for non urban areas. No assumption on the deformation temporal behaviour.!small Baseline Method: (Using a subset) 41000

Method used to improve signal/noise ratio :!Interferograms obtained with DORIS.!Persistent Scatterers : (Hooper et al, 2007) 35500 Optimised for non urban areas. No assumption on the deformation temporal behaviour.!small Baseline Method: (Using a subset) 41000! Combination of both pixel data sets. 54950

Method used to improve signal/noise ratio :!Interferograms obtained with DORIS.!Persistent Scatterers : (Hooper et al, 2007) 35500 Optimised for non urban areas. No assumption on the deformation temporal behaviour.!small Baseline Method: (Using a subset) 41000! Combination of both pixel data sets 54950! Spatio-temporal unwrapping ( 3D )

Unwrapping errors : -21 mm/y 41.9mm/y Mean velocity

Strong tropospheric artefacts : Colima Volcano. Phase/elevation correlation. DEM-SRTM 16/04/2004-05/05/2005 B =5m

Methods to correct this effect: - Temporal filtering. - Continuous GPS data. - Meteorological inputs. - Correlation phase/elevation.

North American Regional Reanalysis data P: Total Pressure T: Temperature e : Partial pressure H 2 O φ tropo = cte * ƒ(k 1 (P/T)+ k 2 (e/t) + k 3 ( e/t 2 ) + k 4 W clouds + k 5 n e /f 2 + n rain ) dz Dry delay Wet delay (k 2 <<k 3 ) δφ tropo / δz = (cte/cos(θ)) * (k 1 (P/T)+ k 2 (e/t) + k 3 ( e/t 2 ) )

North American Regional Reanalysis data Ex: Colima Volcano Dry (k 1 ) Mean total delay (rad/km) Wet 1st order (k 3 ) Wet 2nd order (k2) Total delay

North American Regional Reanalysis data Ex: Colima Volcano Maximum delay 10 rad/km! 4 fringes Track 384 Total delay (rad/km) Track 155

Comparison NARR / correlation phase-elevation elevation. Ex. Colima Volcano Delay (rad/m) NARR. Estimation on wrapped phase.. Interferogram number

Comparison NARR / correlation phase-elevation elevation. Ex. Colima Volcano Delay (rad/m) Interferogram number NARR. Estimation on wrapped phase. Estimation on unwrapped phase. Estimation on unwrapped phase using NARR.

Method applied : - NARR data are used to help unwrapping (removed before and add back after). - 3D Unwrapping *2 - Estimation of tropospheric delays by phase/elevation correlation (+ spatially correlated DEM error). - Correction of the unwrapped phase.

-21 mm/y 41.9mm/y -22.6 mm/y 43.3mm/y Without helping unwrapping Helping unwrapping

19.8 Colima volcano 19.6 19.4 19.2-103.8 Descending track 384-103.6-103.4-103.2 Ascending track 48-103.8-103.6-103.4-103.2-12.1 44.9-4.9 37.2 Mean displacement rate in LOS (mm/y)

19.8 Colima volcano- Summit subsidence Guzman 19.6 Tamazula fault Summit 19.4 19.2-103.8 Descending track 384-103.6-103.4-103.2 Ascending track 48-103.8-103.6-103.4-103.2-12.1 44.9-4.9 37.2 Mean displacement rate in LOS (mm/y)

Colima volcano- Summit subsidence Descending track 384 Descending track 155 Ascending track 48 19.6 19.5 19.4-103.6-103.5-103.6-103.5-103.6-103.5-12.1 44.9-10.2 33.7-5 37.2 Mean displacement rate in LOS (mm/y)

Colima volcano- Summit subsidence 1.68 cm/y -0.27 cm/y 2.81 cm/y 1.63 cm/y 0.07 cm/y Descending track 384

Colima volcano- Summit subsidence Descending track 384 Displacemenet rate (cm/y) 9 µrad Distance from crater center (m) Displacemenet rate (cm/y) 11 µrad Displacemenet rate (cm/y) 14 µrad Distance from crater center (m) Distance from crater center (m)

Explanation - Load and compaction of eruptive products. - Dome load. - Withdrawal of a magma storage zone.

Maximum of displacement is observed around the 1998 lava flow. 39*10 6 m 3 (!2.8 km from the crater center, 20 m thick) (Navarro-Ochoa et al., JVGR, 2002)

Dome load? Descending track 384 19.6 Elastic model : R=130m =40m ρ=2500 kg/m 3 19.5 19.4-103.6-103.5-12.1 44.9 Data -18.5 44.2 Residual velocity Mean displacement rate in LOS (mm/y) E=0.87GPa RMS=5.9mm

Dome load? Displacement in LOS (cm) 03/2003 09/2004 01/2005 Subsidence 1.68 cm/y Time (since 1 st Jan. 2003) 2 domes of 2*10 6 m 3 removed in 3 years

Load of the redistributed domes? Descending track 384 Elastic model: R=1 km =0.4m 19.6 19.6 ρ=2500 kg/m 3 V=1.3 million m 3 /y 19.5 19.5 19.4-103.6 19.4-103.5-103.6-103.5-12.1 44.9 Data Mean displacement rate in LOS (mm/y) -12.4 44.8 Residual velocity E=3GPa RMS=8.6 mm

Withdrawal superficial magma reservoir? Elastic model (Mogi): 19.6 19.6 Descending track 384 H 19.5 19.5 19.4-103.6-103.5 19.4-103.6-103.5 Data Residual velocity -12.1 44.9-13.2 44.8 Mean displacement rate in LOS (mm/y) V=-1.3*10 6 m 3 /y, H=4700m RMS=5.35mm

Chamber withdrawal + load of redistributed domes? Elastic model : 19.6 Descending track 384 1km 19.5 250m 19.4-103.6-103.5-103.6-103.5-12.1 44.9-12.6 44.9 Data Residual velocity Mean displacement rate in LOS (mm/y) V=-0.9*10 6 m 3 /y RMS=5.26mm

After correction (dome( redistributed ted domes load + chamber deflation) Descending track 384 Displacement rate (cm/y) Overcorrected -0.39cm/y Distance from the crater center (m) Displacement rate (cm/y) -0.07cm/y Displacement rate (cm/y) 0.93 cm/y Distance from the crater center (m) Distance from the crater center (m)

Popocatepetl No significant deformation 19.2 19.1 19 Descending track 255 Ascending track 148 18.9-98.8-98.7-98.6-98.5-98.8-98.7-98.6-98.5-10.4 11.2 Mean displacement rate in LOS (mm/y) -8 7.9

Small and localised displacement on the SW flank? 0.47 cm/y Descending track 255-98.8-98.7-98.6-98.5-10.4 11.2 Displacement in LOS (cm) 1 cm/y Time (since 1 st Jan. 2003)

Small and localised displacement on the SW flank? PPX5 PPX6 2 cm of displacement measured by EDM in 1999. PPX - PPX5 0.2500 0.2000 2420 + 0.1500 0.1000 0.0500 0.0000 27/11/ 95 6/03/ 96 14/06 /96 22/09 31/12/ /96 96 10/04 /97 19/07 /97 27/10 4/02/ /97 98 15/05 /98 23/08 /98 1/12/9 11/03/ 8 99 fecha 19/06 27/09 5/01/ /99 /99 00 14/04 /00 23/07 31/10/ 8/02/ /00 00 01 19/05 27/08 /01 /01 PPX - PPX6 PPX 2071 m + 0.6300 0.6200 0.6100 0.6000 0.5900 0.5800 0.5700 0.5600 0.5500 0.5400 27/1 6/03 14/0 22/0 31/1 10/0 19/0 27/1 4/02 15/0 23/0 1/12 11/0 19/0 27/0 5/01 14/0 23/0 31/1 8/02 19/0 1/95 /96 6/96 9/96 2/96 4/97 7/97 0/97 /98 5/98 8/98 /98 3/99 6/99 9/99 /00 4/00 7/00 0/00 /01 5/01 fecha

Conclusions Main difficulty is to removed tropospheric artefacts.! difficult to detect: - small and reversible displacements. - displacements of the same wavelength of the edifice. No evidence of magma injection during period 2003-2006 for the two Mexican strato-volcanoes. Summit deflation at Colima might be explained by the 1998 lava flow load and withdrawal of a magma reservoir at sea level before the last effusive period.