G. Zeni

Uplift and magma intrusion at Long Valley caldera from InSAR and gravity measurements

The Long Valley caldera (California) formed ~760,000 yr ago following the massive eruption of the Bishop Tuff. Postcaldera volcanism in the Long Valley volcanic field includes lava domes as young as 650 yr. The recent geological unrest is characterized by uplift of the resurgent dome in the central section of the caldera (75 cm in the past 33 yr) and earthquake activity followed by periods of relative quiescence. Since the spring of 1998, the caldera has been in a state of low activity. The cause of unrest is still debated, and hypotheses range from hybrid sources (e.g., magma with a high percentage of volatiles) to hydrothermal fluid intrusion. Here, we present observations of surface deformation in the Long Valley region based on differential synthetic aperture radar interferometry (InSAR), leveling, global positioning system (GPS), two-color electronic distance meter (EDM), and microgravity data. Thanks to the joint application of InSAR and microgravity data, we are able to unambiguously determine that magma is the cause of unrest.

Subsidence monitoring in Sarno urban area via multi‐temporal DInSAR technique

In this study Differential Interferometric Synthetic Aperture Radar (DInSAR) is used to investigate the effects of a subsidence phenomenon – related to groundwater withdrawal –on ancient low‐rise masonry buildings located in the urban area of Sarno, Italy. ERS‐1/2 SAR data from 1992 to 2002 were analysed and results were validated with geodetic data. The results encourage future developments for study and use of the multi‐temporal DInSAR technique in the mitigation of subsidence risk.

Stress transfer in the Lazufre volcanic area, central Andes

eruptive centers situated in an area larger than 1800 km 2 and (2) a small-scale uplift located at Lastarria volcano, which is the only volcano to show strong fumarolic activity in decades, with most of the clear deformation apparently not observed before 2000. Both the large and small uplift signals can be explained by magmatic or hydrothermal sources located at about 13 km and 1 km deep, respectively. To test a possible relationship, we use numerical modeling and estimate that the depth inflating source increased the tensile stress close to the shallow source. We discuss how the deep inflating source may have disturbed the shallow one and triggered the observed deformation at Lastarria. Citation: Ruch, J., A. Manconi, G. Zeni, G. Solaro, A. Pepe, M. Shirzaei, T. R. Walter, and R. Lanari (2009), Stress transfer in the Lazufre volcanic area, central Andes, Geophys. Res. Lett., 36, L22303, doi:10.1029/2009GL041276.

Long-term deformation analysis of historical buildings through the advanced SBAS-DInSAR technique: the case study of the city of Rome, Italy

Monitoring of deformation phenomena affecting urban areas and man-made structures is of key relevance for the preservation of the artistic, archaeological and architectural heritage. The differential SAR interferometry (DInSAR) technique has already been demonstrated to be an effective tool for non-invasive deformation analyses over large areas by producing spatially dense deformation maps with centimetre to millimetre accuracy. Moreover, by exploiting long sequences of SAR data acquired by different sensors, the advanced DInSAR technique referred to as the small baseline subset (SBAS) approach allows providing long-term deformation time series, which are strategic for guaranteeing the monitoring of urban area displacements. In this work, we investigate the effectiveness of the two-scale multi-sensor SBAS-DInSAR approach to detect and monitor displacements affecting historical and artistic monuments. The presented results, achieved by applying the full resolution SBAS technique to a huge set of ERS-1/2 and ENVISAT data, spanning the 1992–2010 time interval and relevant to the city of Rome (Italy), show the capability of this approach to detect and analyse the temporal evolution of possible deformation phenomena affecting historical buildings and archaeological sites. Accordingly, our analysis demonstrates the effectiveness of the full resolution multi-sensor SBAS approach to operate as a surface deformation tool for supporting the study and conservation strategies of the historical, cultural and artistic heritage.

Magma and fluid migration at Yellowstone Caldera in the last three decades inferred from InSAR, leveling, and gravity measurements

We studied the Yellowstone caldera geological unrest between 1977 and 2010 by investigating temporal changes in differential Interferometric Synthetic Aperture Radar (InSAR), precise spirit leveling and gravity measurements. The analysis of the 1992–2010 displacement time series, retrieved by applying the SBAS InSAR technique, allowed the identification of three areas of deformation: (i) the Mallard Lake (ML) and Sour Creek (SC) resurgent domes, (ii) a region close to the Northern Caldera Rim (NCR), and (iii) the eastern Snake River Plain (SRP). While the eastern SRP shows a signal related to tectonic deformation, the other two regions are influenced by the caldera unrest. We removed the tectonic signal from the InSAR displacements, and we modeled the InSAR, leveling, and gravity measurements to retrieve the best fitting source parameters. Our findings confirmed the existence of different distinct sources, beneath the brittle-ductile transition zone, which have been intermittently active during the last three decades. Moreover, we interpreted our results in the light of existing seismic tomography studies. Concerning the SC dome, we highlighted the role of hydrothermal fluids as the driving force behind the 1977–1983 uplift; since 1983–1993 the deformation source transformed into a deeper one with a higher magmatic component. Furthermore, our results support the magmatic nature of the deformation source beneath ML dome for the overall investigated period. Finally, the uplift at NCR is interpreted as magma accumulation, while its subsidence could either be the result of fluids migration outside the caldera or the gravitational adjustment of the source from a spherical to a sill-like geometry.

An integrated SAR/GIS approach for investigating urban deformation phenomena: a case study of the city of Naples, Italy

Differential Interferometric Synthetic Aperture Radar (DIFSAR) data have been integrated in a Geographic Information System (GIS) for investigating deformations occurring in urban areas. The proposed approach is based on an extension of the Small Baseline Subset (SBAS) method that allows a proper combination of a large number of DIFSAR data. The obtained deformation measurements are accurately geocoded to achieve an easy merging of DIFSAR products relative to different acquisition geometries and the integration of such products into a GIS. This allows the detection and analysis of displacements of single structures and buildings in the investigated zone. The effectiveness of the approach has been tested on the SAR data acquired by the European Remote Sensing (ERS) satellites relative to the Vomero hill, a district of the city of Naples, Italy.

Conventional and Innovative Techniques for the Monitoring of Displacements in Landslide Affected Area

This work shows a methodological approach for the joint use of geological and geomorphological studies and conventional/innovative monitoring data in densely urbanized areas at landslide risk. The methodology is applied to a test area in the Calabria region (southern Italy) extensively affected by several active landslides involving urban areas. These landslides have been studied and monitored via ground-based techniques for many years. In the study area the comparison and interpretation of DInSAR data with geomorphological studies and inclinometric monitoring has been carried out. The results obtained, thanks to the validation of remote sensed data via ground-truths, provide a further step towards the integrated use of DInSAR data within landslide risk mitigation strategies.

A differential SAR interferometry approach for monitoring urban deformation phenomena

This paper presents a new DIFSAR approach that allows us to detect and follow the temporal evolution of localized deformations. This approach, which is suitable for monitoring single buildings or structures, extends the capability of the algorithm referred to as SBAS technique, originally developed for investigating large scale deformation phenomena. The proposed technique relies on small baseline interferograms only, in order to preserve the DIFSAR capability to provide spatially dense deformation maps; moreover, it requires two different sets of DIFSAR interferograms generated at low (multi-look data) and high (single-look data) spatial resolution, respectively. The algorithm has been tested with data acquired by the European remote sensing (ERS) satellite relative to the area of the city of Napoli (Italy) and the results have been validated by using geodetic data.

Fiber optic based inclinometer for remote monitoring of landslides: On site comparison with traditional inclinometers

Distributed optical fiber sensors, and in particular those based on stimulated Brillouin scattering, have in recent years been the object of a growing attention for structural and environmental monitoring of large areas because they allow to measure strain and temperature profiles up to tens of kilometers with a strain accuracy of ±10ue and a temperature accuracy of ±1°C. In this paper, we present the application of the above sensing principle to the realization and field testing of a novel inclinometer for the measurement of 3D deformation of soil.

Preliminary analysis of a correlation between ground deformations and rainfall: the Ivancich landslide, central Italy

We exploited Differential Synthetic Aperture Radar Interferometry (DInSAR) to investigate the geographical and the temporal pattern of ground deformations in the Ivancich landslide area, Assisi, Italy, in the 18.4-year period April 1992 - September 2010. We used SAR data obtained by the European Remote Sensing (ERS-1/2) satellites in the period April 1992 - July 2007, and SAR data captured by the ASAR sensor on board the Envisat satellite in the period October 2003 - September 2010. We used the Small Baseline Subset (SBAS) technique to process the SAR data, obtaining full resolution measurements for multiple radar targets inside and outside the landslide area, and the history of deformation of the individual targets. The geographical pattern of the ground deformation was found consistent with independent topographic information. The deformation time series of the individual targets were compared to the rainfall history in the area. Results revealed the lack of an immediate effect of rainfall on the ground deformation, and confirmed the existence of a complex temporal interaction between the rainfall and the ground deformation histories in the landslide area. Availability of very long, spatially distributed time series of surface deformation has provided an unprecedented opportunity to investigate the history of the active landslide area.