1. Matteo Albano1, Marco Polcari1, Christian Bignami1, Marco Moro1, Michele Saroli2,1, Salvatore Stramondo1
1 - Istituto Nazionale di Geofisica a Vulcanologia, Via di Vigna Murata 605, Roma (Italy)
2 - Università degli Studi di Cassino e del Lazio meridionale, Via G. di Biasio 43, Cassino (Italy)
Monitoring the change of soil seismic response through the InSAR-derived ground subsidence: application to the Mexico City subsidence

2. Outline Introduction Method The case study Results and validation
Conclusions

3. Central Italy 2016 earthquakes
Introduction
SAR as a ground displacement measurement technique
EARTHQUAKES
Central Italy 2016 earthquakes
(INGV, 2016)
Campi Flegrei (Trasatti et al., 2015)
VOLCANOS
Subsidence of Bologna
(Stramondo et al., 2007)
ANTHROPOGENIC PHENOMENA

4. Introduction Urban subsidence caused by groundwater withdrawal
Bologna (Stramondo et al., 2007)
Morelia (Cigna et al., 2012)
Guzman (Brunori et al., 2012)
Thessaloniki (Svigkas et al., 2016)
Effect on the dynamic behavior of soils

5. Introduction Effect on the dynamic behavior of soils: theory Soil RockHs vs a t a t vs
DHs
Rock
Soil
Uniform, damped soil on a rigid rock
Hs = soil thickness
Vs = shear wave velocity a t
Amplification factor
Frequency (w)
(Kramer, 1996) 2 4 6 8 10 12 5 15 20
𝐴= 1 𝑐𝑜𝑠 2 𝜔𝐻 𝑣 𝑠 + [𝜉 𝜔𝐻 𝑣 𝑠 ] 2
𝜔 𝑛 = 𝑣 𝑠 𝐻 𝑠 𝜋 2 +𝑛𝜋 ; 𝑛=0, 1,…,∞
𝜔 0 = 𝜋 𝑣 𝑠 2𝐻 𝑠
n = 0
𝑇 𝑠 = 2𝜋 𝜔 0 = 4 𝐻 𝑠 𝑣 𝑠 Hs Ts

6. Introduction
Effect on the dynamic behavior of soils: experimental evidence
Mexico city (Avilés and Pérez-Rocha, 2010; Arroyo et al., 2013)
ALAMEDA PARK – CITY CENTER
Fourier amplitude (m/s)
Ts(s)
Ts(s)

7. InSAR ground subsidence as a tool for local seismic hazard monitoring
Objective
Urban subsidence from InSAR
Ts(s)
Change of the soil resonant period
InSAR ground subsidence as a tool for local seismic hazard monitoring

8. InSAR displacements t0  tn
Method
InSAR displacements t0  tn
Soil resonant period
Ts (tn)
Soil thickness Hs (tn)
(Gosar and Lenart, 2010)
𝐻 𝑠 =𝑎∙ 𝑇 𝑠 𝑏
𝐻 𝑠 =𝑎∙ 𝑇 𝑠 𝑏
Ts ???
Soil thickness (t0)
𝐻 𝑠 =𝑎∙ 𝑇 𝑠 𝑏

9. The case study MEXICO CITY Land area:1485 km2 8.84 million people
Density: 6000 people/km2

10. The case study Seismic hazard http://gmo.gfz-potsdam.de/ Urban area
Hard volcanic deposits
Alluvial fans
Clays and clayey silts
Urban area
The Global Seismic Hazard Map
2280
2260
2240
2220
2200
2180
2160
2140
Height a.s.l. (m)
Hs  60m
Santoyo et al., 2005

11. The case study Ground subsidence SAR data Leveling GPS data
Cabral-Cano et al., 2008
Leveling
GPS data
Cabral-Cano et al., 2008
Sowter et al., 2016
López-Quiroz et al., 2009
(Osmanoglu et al., 2011)
Chaussard et al., 2014

12. The case study A-priori data Soil thickness (Hs)
NORMAS TECNICAS COMPLEMENTARIAS DEL REGLAMENTO DE CONSTRUCCIONES DEL DISTRITO FEDERAL (November 2004)
Soil thickness (Hs)
Soil resonant period (Ts)
Design response spectrum
(Avilés & Pérez-Rocha, 2010)

13. Results and validation
SAR data and results
ENVISAT
RADARSAT-2
Constellation
ENVISAT
RADARSAT-2
Time interval
November,2004
February,2006
April,2013
September,2013
Image n° 13 10
Sensor
C-band
Mode
Stripmap
tilde IW-mode
Resolution
100 m
Orbit
Descending
Incidence angle
23°
35°
SBAS
(Berardino et al., 2002)
IPTA
(Werner et al., 2003)

14. Results and validation
Soil thickness (Hs)
2004
2013
Variation between

15. Results and validation
Soil resonant period (Ts)
2004
2013
Variation between

16. Design response spectrum
Results and validation
Soil resonant period (Ts)
Variation between
Design response spectrum

17. Results and validation
27 accelerometric stations (Arroyo et al., 2013)
RMSE = 0.2s
AE02
BO39
PE10
CJ03

18. Conclusions
We developed a procedure to evaluate the effect of ground subsidence on the spatial and temporal seismic response of soils by exploiting InSAR-derived ground displacements.
The proposed procedure has been applied to estimate the resonant period change of the subsoil of Mexico City caused by the very fast subsidence which affects the city.
The resonant period estimates have been validated with field measurements.
The results can be improved by processing a complete SAR dataset from 2005 to 2017
The proposed procedure is suitable for the on-line implementation.