Ground deformation monitoring and source analysis

We provide tailored services and information products for the monitoring of the ground motions and for the generation of models and scenarios, aiding in the deformation source analysis

Monitoring Products

Depending on application, required precision and site extent and location, we provide a comprehensive portfolio of ground deformation monitoring products and services, ranging from very local optical leveling surveys, to local/regional Continuous GPS network data analysis (we can also deploy a GPS network for you!), to high resolution ground displacement maps obtained from satellite radar missions. We use state of the art geodetic and remote sensing analysis methods.

Product What is it Type of service
Co-seismic ground deformation map It is a map showing at each location the amount of ground motion (in cm) due to a moderate to large earthquake.  Routine, one time, near real time (after image acquisition).
Inter-seismic ground deformation map It is a map showing the yearly rate of ground motion (ground velocity, in mm/yr) occurred within a specified time period. For each measurement point the time series of the ground displacement is also provided.  Routine, one time.
Volcano ground deformation map (Pre-eruptive & Sin-eruptive) It is a map showing for each location of a volcanic area the yearly rate of ground motion (ground velocity, in mm/yr) due to magma or fluid accumulation or release.For each measurement point the time series of the ground displacement is also provided.  Routine, one time, near real time (after image acquisition).
Land subsidence map It is a map showing the yearly rate of ground lowering (in mm/yr) generally due to fluid withdrawal from the subsoil.For each measurement point the time series of the ground displacement is also provided.The high resolution versions of this product are also used to monitor sinkholes, mining-induced ground deformation,  cave collapses, and other local phenomena.  Routine, one time, near real time (after image acquisition).
Active landslide map It is a map showing for a landslide-prone area the yearly rate of ground motion (in mm/yr) due to gravitational slope movements.For each measurement point the time series of the ground displacement is also provided.  Routine, one time, near real time (after image acquisition).


Co-seismic ground deformation map

The source of an earthquake is a fault rupture, or dislocation, in the Earth’s crust. Using radar and optical satellite data we measure the permanent ground movements caused by the fault displacements.

Large earthquakes can generate fault scarps, topographic steps up to 10 meters high and tens of km long, able to destroy or damage the structures they cross. Even moderate earthquakes generate diffuse, permanent surface deformation, which may be  invisible to the eye but can strongly affect the hydrological regime, and cause for instance inundation of sunken areas, increased erosion or land sliding of uplifted ones.

During an emergency, the co-seismic ground deformation map and its derived products are an important piece of information for disaster managers, used for the environmental damage assessment and the situational awareness. We provide this information  in near real time (once images are available) using data from a variety of radar and optical satellites, and different analysis methods. We also use GPS networks and data, depending on location.

Cefalonia Earthquake
The figure shows the ground displacement caused by the February 3, 2014 Cephalonia earthquake, Greece, obtained from radar satellite images and GPS geodetic data (Merryman Boncori et al., 2015)

 

Inter-seismic ground deformation map

During the inter-seismic period the faults accumulate tectonic stress which is periodically released by earthquake ruptures. The slow build-up of crustal deformation can be measured at the surface and used to predict the long-term rate of fault activity. Risk managers then use these slip rates to constrain seismic hazard assessment.
We provide inter-seismic ground deformation measurements, as displacement time series and mean velocities, using multi-temporal image datasets from a variety of radar satellites and permanent/survey-mode GPS data.

Seismic Ground Velocity
The inter-seismic ground velocity across the Western Doruneh Fault in Central Iran (red line across the image)

The map above shows the inter-seismic ground velocity across the Western Doruneh Fault in Central Iran (red line across the image). The black box in the map shows the location of the buffered velocity profile (right image). These data were modeled to provide important information for seismic hazard assessment, as fault kinematics and slip rate (Pezzo et al., 2012).

Ground deformation measurements of volcanoes
Surface deformation in volcanic areas is caused by pressure variation of volcanic fluids (magma, gases) inside the volcano plumbing system (magma chambers, conduits, dykes). For this reason ground deformation is one of the possible precursors of a volcanic eruption, and is a parameter normally monitored over many world volcanoes, with variable resolution and accuracy.
We can provide high resolution and accurate ground deformation measurements of volcanic areas using radar and optical satellite imagery and permanent/survey-mode GPS data. These data are needed by risk managers to detect changes which may suggest a progress towards volcanic unrest.
Once the eruption is started, ground deformation measurements are needed to model the magmatic source, and to estimate the duration of the phenomena, since the rate of outflow of magmatic material is related to the rate of deflation of the volcanic edifice. Given the fast dynamic behaviour of volcanic eruptions, this monitoring service may require frequent updates, obtained using a variety of satellite sensors.

Land subsidence measurements
Land subsidence due to underground fluid withdrawal (more commonly water, but also oil and gas) is increasingly a problem in many urban areas of the world. Very high ground lowering rates (up to tens of cm/yr) are increasing the risk of sea or river inundation for millions of people in many basin and coastal cities. In these contexts flood prevention measures by risk managers need to consider subsidence rates and patterns. The temporal evolution of land subsidence is also an essential parameter for groundwater exploitation planning by city managers.
At a more local scale land subsidence may occur due to sinkhole or cave collapse, or mining operations.
We provide accurate subsidence rates at various scales and accuracy levels, using multi-temporal image datasets obtained from a variety of radar satellites, and GPS data.

The figure shows the land subsidence occurring in the Bandung city, West Java  in the period 2017-2011, as obtained from radar images from the Japanese satellite ALOS-1. Ground displacement time series suggest a decreasing subsidence rate in the last period.
The figure shows the land subsidence occurring in the Bandung city, West Java in the period 2017-2011, as obtained from radar images from the Japanese satellite ALOS-1. Ground displacement time series suggest a decreasing subsidence rate in the last period.

Active landslide map

Ground deformation is certainly the most evident expression of landslide collapse. However, the monitoring of ground movements on slopes can be effectively used to map and characterise active sliding masses before collapse. In landslide-prone regions, risk managers and local administrations need this information to plan effective prevention measures and implement warning systems.
Landslide dimensions are normally 1-2 order of magnitude smaller than faults or volcanoes, and for this product we use high resolution optical and radar image data.
We can also provide ground displacement time series for monitoring the landslide evolution.

The figure shows the slow ground deformation affecting the steep rocky slopes of a mountain range in the Central Apennine, as measured using a large dataset of ENVISAT radar images (Moro et al., 2009).
Slow ground deformation affecting the steep rocky slopes of a mountain range in the Central Apennine, as measured using a large dataset of ENVISAT radar images (Moro et al., 2009).

 

Models and scenarios
The analysis of the different sources of ground deformation is carried out using analytical and numerical models constrained and validated using the ground motion observations and whatever other information is available on the medium and source behaviour.
We provide models generated using state-of-the-art scientific analysis methods, for the following sources and geophysical parameters.

Models and Scenarios What is it Type of service
Seismic source models It is a representation of the geometry and kinematics of the source of an earthquake. The knowledge of the seismic source location and parameters is an essential piece of information for the emergency management. Near real time (after image acquisition).
Slip rate on active faults It is the geologically averaged velocity of dislocation of an earthquake fault. The slip rate is an important parameter for seismic hazard assessment. One time.
Co-seismic ground deformation scenario It is a map of the simulated ground motions generated by any earthquake on a given fault. It is an important tool for seismic risk prevention. Routine, one time.
Stress transfer on faults surrounding a large earthquake It is calculated after a large earthquake to investigate which of the nearby active faults have been further loaded by the stress transferred by the seismic dislocation. Routine, one time, near real time (after image acquisition).
Triggered landslide scenario It is a map showing the distribution of the largest slope displacements theoretically triggered by a given earthquake. Routine, one time.


Seismic source models

The characterisation of the seismic source is rapidly needed for the situational awareness following an earthquake, to address the possibility of further impacts, as large aftershocks caused by slippage of locked fault patches, post-seismic increase of surface deformation along damaging surface fault scarps, or simply to update the hazard models for the region.
We can provide accurate seismic source models based on the geophysical inversion of the co-seismic deformation field obtained from InSAR and GPS data. We use state of the art modeling procedures to characterise the source location, geometry, extension and 3D fault slip vector. We also use any additionally available information to validate the model.

The reconstruction of the fault segments which caused the Darfield, New Zealand earthquake of  September 4, 2010 (Atzori & Antonioli, 2011).
The reconstruction of the fault segments which caused the Darfield, New Zealand earthquake of September 4, 2010 (Atzori & Antonioli, 2011).

 

Slip rate on active faults
The long term average slip rate of an active fault is defined as the total fault slip occurring during large earthquakes divided by the recurrence interval over geological times.
The slip rate provides the long term representation of the fault activity, and is an important quantity for seismic hazard assessment. It can also be estimated from crustal deformation rates obtained from InSAR and GPS geodetic data and geophysical modeling procedures.
We provide estimates of fault slip rates for large active faults for which satellite measurements of inter-seismic strain accumulation can be obtained. We also provide validation of the present day slip rate with all the available ancillary information from geological and geomorphological data.

Co-seismic ground deformation scenario
Simulations of the static co-seismic surface deformation induced by earthquakes are important for Risk Managers to assess the effects of earthquakes on man made structures, and take appropriate prevention measures.
We provide tailored co-seismic ground deformation scenarios obtained through an elastic modeling procedure of the rupture causing an earthquake.

The figure shows the vertical co-seismic ground displacement scenario simulated for a magnitude 6.8 earthquake on the Lembang Fault, West Java Indonesia. Several linear infrastructures would be disrupted by a 2.5-3 m high surface fault scarp.
The figure shows the vertical co-seismic ground displacement scenario simulated for a magnitude 6.8 earthquake on the Lembang Fault, West Java Indonesia. Several linear infrastructures would be disrupted by a 2.5-3 m high surface fault scarp.

 

Stress transfer on faults surrounding a large earthquake
During the sudden crustal rupture process which causes an earthquake, a portion of the pre-existing tectonic stress is redistributed in the crust, and it can increase or decrease the pre-existing stress levels in the neighbouring areas. It has been noted that after large earthquakes, further aftershocks or even new large mainshocks have a higher probability to occur in areas of positive stress variations.
We provide maps showing the stress variations caused by large seismic ruptures, in a crustal volume or on specific active faults. This information can be of important use during a seismic emergency.

Stress variations caused by the Northern Italy (2012) seismic sequence mainshock fault (the black rectangle) on nearby active faults. Rupture of the fault no.2 occurred 9 days after the mainshock and caused increased casualties and damage.
Stress variations caused by the Northern Italy (2012) seismic sequence mainshock fault (the black rectangle) on nearby active faults. Rupture of the fault no.2 occurred 9 days after the mainshock and caused increased casualties and damage (Pezzo et al., 2013).

Triggered landslide scenario
In particular geologic conditions landslides triggered by seismic shaking can cause most of the earthquake’s damage. We provide regional triggered landslide scenarios using the sliding-block method developed by Newmark and Ambraseys and its further improvements.