Warning systems: alert thresholds

Size: px

Start display at page:

Download "Warning systems: alert thresholds"

Elmer Osborne
7 years ago
Views:

1 Department of Earth Sciences CENTRE OF COMPETENCE OF THE CIVIL PROTECTION DEPARTMENT PRESIDENCY OF THE COUNCIL OF MINISTERS Warning systems: alert thresholds Nicola Casagli Giovanni Gigli, Veronica Tofani

2 Presentation structure Theory: predicting the time of failure using monitoring time series, from Apollonius of Perga to nowadays Example #1: Monte Beni rockslide, a case of successful prediction Example #2: Ruinon: on-going monitoring and early-warning of the most dangerous rockslide in Italy Example #3: Stromboli: real-time forecasting of slope instability and volcano eruptions Example #4: Urban landslides in Calabria Region: from prediction to governance

3 Apollonius of Perga (Perga, 262 a.c. Murtina, 190 a.c.) The Conics

4 The hyperbolas

5 Saito (1965) Method to predict failure based on creep rupture Linear relationship between inverse velocity and time during periods of acceleration to failure (i.e. hyperbolic acceleration) 1/velocity Time of failure 0 Time

6 Landslide behaviour Time t t f = objective of prediction Velocity v Limit equilibrium New limit equilibrium (hyperbolic) acceleration collapse

7 Fukuzono (1985) Power law relationship between acceleration and velocity before failure, tested on laboratory physical models d dt 2 x 2 = A dx dt α for α >1: ( t t ) f i = ( ) 1 α v ( v ) f A i ( 1 α ) 1 α

8 Inverse-velocity method Fukuzono (1985) v f 1 = 1 = ) α v f i 1 1 [ ( )] 1 A α 1 α ( t t If α = 2 : V -1 = A(t f -t) HYPERBOLA

9 Barry Voight (1988) A relation to describe rate-dependent material failure Science (1988) A method for prediction of volcano eruptions Nature (1988) May 1980, Mt. St. Helens volcano July 1995, Montserrat's Soufriere Hills volcano

10 Generalized Saito law Voight (1991) Ω Ý α Ω Ý A = 0 Ω= any appropriate material quantity A and α = experimental material constants Dots refer to differentiation with respect to time

11 Vajont, 1963 Voight (1991)

12 Mt. St. Helens, 1980 Voight (1991)

13 Azimi graphical method Azimi et al. (1988)

14 Some examples Rose & Hungr (2006)

15 La Clapiere Rose & Hungr (2006)

16 Open pit mine applications (Rose & Hungr, 2006) Landslide volume: 18 milion m 3

17 Stabilization progress monitoring (Rose & Hungr, 2006)

18 Vajont 1963 Hendron & Patton (1985)

19 Vaiont landslide Hutchinson (2001)

20 Vajont landslide Hutchinson (2001)

21 Unexpected failures Hutchinson (2001) Measurement error Random noise Local movements Anthropic activity Earthquakes Meteorologic factors Structural constraints Brittle failure Invalid assumptions

22 Non linearity Petley (2003) Data from A: Angeli et al. (1989); B: Salt (1985); C: CNR IRPI (2002); D: USGS (2002)

23 Non linearity Petley (2003) Two styles of accelerating behaviour are seen in landslides Linearity = rupture surface development / brittle failure / first-time failures Asymptotic = sliding on existing surfaces / ductile deformation / continuous or reactivated failures These considerations are based on a new model for the development of progressive failure in brittle landslides tested in laboratory

24 My personal experience Casagli (today) The linear model applies to the most part of slope failures (both first time and reactivations) in a simple geological environment (i.e. with a single main driving factor of instability) Non-linear (asympthotic) behaviour has been observed in first time failures during volcano eruptions In many cases reactivated failures exhibit a brittle behavior (related to the linear model) Key reference: HUTCHINSON J.N. (1987) - Mechanisms producing large displacements in landslides on pre-existing shears. 1st Sino- British Geol. Conf., Tapei, Memoir of the Geological Survey of China, 9,

25 Example #1: Monte Beni

26 Montebeni (Italy) April 19 th 2002

27 Perimetral crack

28 MASSIVE BASALTS THRUST SURFACE WITH LAMINATED CHERTS BASALT BRECCIAS VEGETATED SLOPE DEPOSITS DISTURBED BRECCIAS LIMESTONES debris cone debris cone debris cone Basalt Basalt breccias Tectonically disturbed breccias Thrust fault Bedded limestones talus Caothic clay shales bedding

29 Monitoring with distometers

30 Ground-based InSAR target area Continuous-wave stepped-frequency (CW-SF) radar based on a Network Analyser (NWA) operating in the frequency band GHz Tx Rx sled linear rail 2.8m source NWA computer The synthetic aperture is obtained sliding the antennas along a linear rail European Commission Joint Research Centre

31 Target visibility LiSA can operate in any condition of visibility (eg. during night, rainstorms and fog)

32 LISA Applications: Monte Beni landslide 08/05/ :12 09/05/ /05/ /05/ /05/ /05/ :59 17: :37 00:07 04:00 06:35 08:40 14:05 16:50 19:20 23:55 03:10 05:50 09:45 11:52 13:50 16:45 19:00 21:20 23:42 02:45 06:00 08:30 11:20 14:30 17:35 20:10 22:40 02:15 05:46 08:55 12:40 15:40 Start: 8/5/ :59 End: 13/5/ :12 Interval: 124 h Acquisition time: 40 min Peak velocity: 0.48 mm/h LOS DISPLACEMENT (mm) Mean Velocity: 0.16 mm/h

33 Displacement histories m point 2 point 3 point 4 DISPLACEMENT (mm) cumulated displacement (mm) point 1: displacement = 57 mm velocity = 11 mm/day cumulated displacement (mm) point 2: displacement = 37 mm velocity = 7 mm/day point 1 point 5 m elapsed time (min) elapsed time (min) cumulated displacement (mm) point 3: displacement = 25 mm velocity = 5 mm/day cumulated displacement (mm) point 4: displacement = 22 mm velocity = 4 mm/day cumulated displacement (mm) point 5: displacement = 13 mm velocity = 3 mm/day elapsed time (min) elapsed time (min) elapsed time (min)

34 November 2002: early warning system Traffic light 1 Traffic light 2 Network of wire extensometers, bar extensometers and clinometers Displacement thresholds which activate two traffic lights

35 Early December: failure of sensors area 1 area mm (cm per AL), c DR1 DR2 EF1 FA1 FA2 AL1 TA1 mm, cm per AL, c DR5 FA4 FA5 FA6 EF4 TA2 DR /11/ /12/ /12/ /12/ /12/ /12/ /12/ /12/ /12/ /12/ /12/ data /11/02 29/11/02 1/12/02 3/12/02 5/12/02 7/12/02 data 9/12/02 11/12/02 13/12/02 15/12/02 17/12/02 19/12/02 area2 area mm, cm per AL, c DR3 DR4 EF2 EF3 FA3 AL3 AL2 TA2 mm, c EF5 EF6 EF7 TA /11/ /12/ /12/ /12/ /12/ /12/ /12/ /12/ /12/ /12/ /12/ /11/02 28/11/02 29/11/02 30/11/02 1/12/02 2/12/02 3/12/02 4/12/02 5/12/02 6/12/02 7/12/02 8/12/02 data data

36 Monitoring time series Cumulated displacement (mm) delta 1-2 delta 3-2 delta 12-8 delta a'-b' delta 34-35' delta delta InSAR monitoring Extensometer monitoring collapse 0 4/4 24/4 14/5 3/6 23/6 13/7 2/8 22/8 11/9 1/10 21/10 10/11 30/11 20/12

37 Inverse velocity method /v1-2 1/v3-2 1/v12-8 1/va'-b' 1/v34-35' 1/v /v /v (giorno/mm) collapse /9 9/9 17/9 25/9 3/10 11/10 19/10 27/10 4/11 12/11 20/11 28/11 6/12 14/12 22/12 30/12 7/1

38 Inverse velocity method Benchmarks /v (giorno/mm) failure /7 23/7 2/8 12/8 22/8 1/9 11/9 21/9 1/10 11/10 21/10 31/10 10/11 20/11 30/11 10/12 20/12 30/12

39 Azimi graphical method 19-gen 30-dic Benchmarks dic 20-nov 31-ott 11-ott 21-set 01-set 01-set 11-set 21-set 01-ott 11-ott 21-ott 31-ott 10-nov 20-nov 30-nov 10-dic 20-dic 30-dic 09-gen

40 Dispatches to civil protection authorities The landslide, until now sensitive to rainfall, is now increasing its rate of displacement independently from precipitation (letter of Prof. Canuti to the Mayor of Firenzuola, November 26 th, 2002) The main landslide is on the point of collapsing. It is necessary that the evacuation measures will be strictly respected during Christmas holidays (letter of Prof. Canuti to the Mayor of Firenzuola, December 23 rd, 2002) The main landslide will collapse within the first days of January 2003 (report of Prof. Canuti to the Civil Protection Commission, December 27 th, 2002)

41 Numerical model of failure

42 Risk scenario Perimetral crack Regional road Landslide volume: m 3 Angle of friction: 34 Graphical elaboration: Conefall (

43 Rock fall of m 3 December 14 th 2002

44 December 15 th 2002 Intitiation of the major collapse

45 December 28 th 2002 Collapse of m 3 of rock

46 Today

SAR INTERFEROMETRY MONITORING OF LANDSLIDES ON THE STROMBOLI VOLCANO

SAR INTERFEROMETRY MONITORING OF LANDSLIDES ON THE STROMBOLI VOLCANO Antonello G. (1), Casagli N. (2), Farina P. (2), Guerri L. (2), Leva D. (3), Nico G. (3), Tarchi D. (1) (1) European Commission, Joint