Measurement of coseismic deformation by satellite geodesy

GDR STRAINSAR (2000-2005) 98 peer-reviewed publications

Alsdorf, D. E., J. M. Melack, T. Dunne, L. A. K. Mertes, L. L. Hess, and L. C. Smith, Interferometric radar measurements of water level changes on the Amazon floodplain, Nature, 404, 174-177,, 2000.

Alsdorf, D. E., L. C. Smith, and J. M. Melack, Amazon water level changes measured with interferometric SIR-C radar, IEEE Transactions on Geoscience and Remote Sensing, in press, 2000.

Amelung, F., and J. W. Bell (2003), Interferometric synthetic aperture radar observations of the 1994 Double Spring Flat, Nevada earthquake (M 5.9): Mainshock accompanied by triggered slip on a conjugate fault, J. Geophys. Res., 108, 2433, doi:2410.1029/2002JB001953.

Amelung, F., C. Oppenheimer, P. Segall, and H. Zebker, Ground deformation near Gada 'Ale Volcano, Afar, observed by Radar Interferometry, Geophys. Res. Lett., 3093-3096, 27, 2000.

Arnadottir, T., R. Pedersen, S. Jonsson, and G. Gudmundsson (2003), Coulomb stress changes in the South Iceland Seismic Zone due to two large earthquakes in June 2000, Geophys. Res. Lett., 30, doi:10.1029/2002GL016495. The South Iceland Seismic Zone experienced the largest earthquakes for 88 years in June 2000, with a MS = 6.6 event on June 17, followed by another MS = 6.6 earthquake on June 21. These events occurred on two parallel N-S striking, right-lateral strike slip faults, separated by about 17 km. We calculate the static Coulomb stress change for the June 17 and 21 earthquakes using a distributed slip model derived from joint inversion of InSAR and GPS data. We find that the static stress change caused by the June 17 event is about 0.1 MPa at the location of the June 21 hypocenter, promoting failure on the second fault. Locations of aftershocks agree well with areas of increased Coulomb failure stress. Our calculations indicate that positive stress changes due to the two earthquakes make the area west of the June 21 rupture the most likely site of the next large earthquake in South Iceland. doi:10.1029/2002GL016495

Árnadóttir, T., H. Geirsson, and P. Einarsson (2004), Coseismic stress changes and crustal deformation on the Reykjanes Peninsula due to triggered earthquakes on 17 June 2000, Journal of Geophysical Research (Solid Earth), 109, 09307. A large (Mw = 6.5) earthquake struck the South Iceland Seismic Zone (SISZ) on 17 June 2000. The 17 June main shock triggered increased seismicity over a large area and significant slip on at least three distinct faults on the Reykjanes Peninsula, up to 87 km to the west of the event. A second large (Mw = 6.4) earthquake in the SISZ occurred on 21 June 2000, about 17 km west of the 17 June main shock. This event does not appear to have triggered as much activity on the Reykjanes Peninsula as the 17 June main shock, although the epicenter was closer. Crustal deformation signals due to the June 2000 earthquakes on the Reykjanes Peninsula were observed with campaign and continuous GPS and synthetic aperture radar interferometry, with the largest coseismic deformation signal near lake Kleifarvatn. We model the faults using three uniform slip rectangular dislocations in an elastic half-space. Best fit uniform slip models consistent with seismic and geodetic data indicate that all three faults trend N-S and the motion on them was primarily right-lateral strike slip. Our study suggests that the event near Kleifarvatn had a significantly larger moment than seismic estimates, indicating a component of aseismic slip on the fault lasting no more than several hours. Static Coulomb failure stress change calculations indicate that the event at Kleifarvatn increased the Coulomb stress at the hypocenter of the Núpshlídarháls event by 0.1-0.2 MPa as well as loading the Hvalhnúkur fault.

Baumont, D., O. Scotti, F. Courboulex, and N. Melis (2004), Complex kinematic rupture of the Mw 5.9, 1999 Athens earthquake as revealed by the joint inversion of regional seismological and SAR data, Geophysical Journal International, 158, 1078-1087. Slip distributions of the moderate magnitude (Mw 5.9), 1999 Athens earthquake, inverted from surface waves and interferometric Synthetic Aperture Radar (SAR) images, show very different characteristics. The robustness analysis proposed in this study, confirms the discrepancy between the well-constrained features of each individual solution. Irrespective of the hypotheses we made (data/modeling errors, slow deformation, post- or pre-seismic slip), the joint inversion of the two data sets led to a complex and heterogeneous rupture model. This model is characterized by a short rise time (<5 s) slip patch centred on the hypocentre, extending bilaterally up to 4 km depth and down to 17 km and releasing approximately 70 per cent of the total moment. Located further to the WNW and releasing the remaining 30 per cent of the total moment, a long rise time slip patch extends from 8 to 17 km depth. If the short rise time slip patch propagated above and below the brittle zone delineated by the aftershocks, the long rise time slip patch (slow deformation) appears to be mostly confined below the brittle zone. This unified model satisfies the analysis of the seismic and geodetic slip distributions as well as the location of the aftershock sequence and attests to the diversity of the crustal response even for moderate size faults.
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2004GeoJI.158.1078B&db_key=AST

Bawden, G. W., W. Thatcher, R. S. Stein, K. W. Hudnut, and G. Peltzer (2001), Tectonic contraction across Los Angeles after removal of groundwater pumping effects, Nature, 412, 812 - 815. After the 1987 Whittier Narrows and 1994 Northridge earthquakes revealed that blind thrust faults represent a significant threat to metropolitan Los Angeles, a network of 250 continuously recording global positioning system (GPS) stations was deployed to monitor displacements associated with deep slip on both blind and surface faults. Here we augment this GPS data with interferometric synthetic aperture radar imagery to take into account the deformation associated with groundwater pumping and strike-slip faulting. After removing these non-tectonic signals, we are left with 4.4 mm yr-1 of uniaxial contraction across the Los Angeles basin, oriented N 36° E (perpendicular to the major strike-slip faults in the area). This indicates that the contraction is primarily accommodated on thrust faults rather than on the northeast-trending strike–slip faults. We have found that widespread groundwater and oil pumping obscures and in some cases mimics the tectonic signals expected from the blind thrust faults. In the 40-km-long Santa Ana basin, groundwater withdrawal and re-injection produces 12 mm yr-1 of long-term subsidence, accompanied by an unprecedented seasonal oscillation of 55 mm in the vertical direction and 7 mm horizontally. http://www.nature.com/nlink/v412/n6849/abs/412812a0_fs.html

Beauducel, F., P. Briole, and J. L. Froger, Volcano wide fringes in ERS synthetic aperture radar interferograms of Etna: Deformation or tropospheric effect?, J. Geophys. Res., 105, 16,391-16,402, 2000.

Beauducel, F., P. Briole, J.-L. Froger, and D. Rémy, SAR Interferometry studies of Mt Merapi, Java, Indonesia, Report to ESA 2000.

Berthier, E., H. Vadon, D. Baratoux, Y. Arnaud, C. Vincente, K. L. Feigl, F. Remy, and B. Legresy (2004), Surface motion of mountain glaciers derived from satellite optical imagery, Remote Sensing of Environment, in press. A complete and detailed map of the ice-velocity field on mountain glaciers is obtained by cross-correlating SPOT5 optical images. This approach offers an alternative to SAR interferometry, because no present or planned RADAR satellite mission provides data with a temporal separation short enough to derive the displacements of glaciers. The methodology presented in this study does not require ground control points (GCPs). The key step is a precise relative orientation of the two images obtained by adjusting the stereo model of one slave image assuming that the other master image is well georeferenced. It is performed with numerous precisely-located homologous points extracted automatically. The strong ablation occurring during summer time on the glaciers requires a correction to obtain unbiased displacements. The accuracy of our measurement is assessed based on a comparison with nearly simultaneous differential GPS surveys performed on two glaciers of the Mont Blanc area (Alps). If the images have similar incidence angles and correlate well, the accuracy is on the order of 0.5 m, or 1/5 of the pixel size. Similar results are also obtained without GCPs. An acceleration event, observed in early August for the Mer de Glace glacier, is interpreted in term of an increase in basal sliding. Our methodology, applied to SPOT5 images, can potentially be used to derive the displacements of the Earth’s surface caused by landslides, earthquakes, and volcanoes.

Carnec, C., and C. Delacourt, Three years of mining subsidence monitored by SAR interferometry, Gardanne, France, Applied Geophysics, 43, 43-54, 2000.

Catita, C., J. Catalão, J. M. Miranda, K. L. Feigl, and L. A. Mendes-Victor (2004), Co-seismic Deformation of the 9th July 1998 Faial (Azores) Earthquake Detected by Radar Interferometry, Int. J. Rem. Sensing, in press.

Champollion, C., F. Masson, J. Van Baelen, A. Walpersdorf, J. Chéry, and E. Doerflinger (2004), GPS monitoring of the tropospheric water vapor distribution and variation during the 9 September 2002 torrential precipitation episode in the Cévennes (southern France), Journal of Geophysical Research (Atmospheres), 109, 24102. On 8-9 September 2002, torrential rainfall and flooding hit the Gard region in southern France causing extensive damages and casualties. This is an exceptional example of a so-called Cévenol episode with 24 hour cumulative rainfall up to about 600 mm at some places and more than 200 mm over a large area (5500 km^2 ). In this work we have used GPS data to determine integrated water vapor (IWV) as well as horizontal wet gradients and residuals. Using the IWV, we have monitored the evolution of the convective system associated with the rainfall from the water vapor accumulation stage through the stagnation of the convective cell and finally to the breakup of the system. Our interpretation of the GPS meteorological parameters is supported by synoptic maps, numerical weather analyses, and rain images from meteorological radars. We have evidenced from GPS data that this heavy precipitation is associated with ongoing accumulation of water vapor, even through the raining period, but that rain stopped as soon as the weather circulation pattern changed. The evolution of this event is typical in the context of the Cévenol meteorology. Furthermore, we have shown that the horizontal wet gradients help describe the heterogeneity of the water vapor field and holds information concerning the passage of the convective system. Finally, we have noticed that the residuals, which in theory should be proportional to water vapor heterogeneity, were also highly perturbed by the precipitation itself. In our conclusions we discuss the interest of a regional GPS network for monitoring and for future studies on water vapor tomography. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2004JGRD.10924102C&db_key=PHY

Chlieh, M., J. B. de Chabalier, J. C. Ruegg, R. Armijo, R. Dmowska, J. Campos, and K. L. Feigl (2004), Crustal deformation and fault slip during the seismic cycle in the North Chile subduction zone, from GPS and InSAR observations, Geophysical Journal International, 158, 695-711. The different phases of the earthquake cycle can produce measurable deformation of the Earth's surface. This work is aimed at describing the evolution of that deformation in space and time, as well as the distribution of causal slip on the fault at depth. We have applied GPS and synthetic aperture radar (SAR) interferometry (InSAR) techniques to northern Chile, where fast plate convergence rates are associated with large subduction earthquakes and extensive crustal deformation. The region of northern Chile between 18°S and 23°S is one of the most important seismic gaps in the world, with no rupture having occurred since 1877. In 1995, the Mw = 8.1 Antofagasta earthquake ruptured the subduction interface over a length of 180 km in the region immediately to the south of this 450 km long gap. The coseismic deformation associated with this event has been documented previously. Here we use GPS position time-series for 40 benchmarks (measured between 1996 and 2000) and ERS SAR interferograms (for the interval between 1995 and 1999) to map both the post-seismic deformation following the 1995 event and the ongoing interseismic deformation in the adjacent gap region. In the seismic gap, the interseismic velocities of 20-30 mm yr^-1 to the east with respect to South America are mapped. Both the GPS and the InSAR measurements can be modelled with 100 per cent coupling of the thrust interface of the subduction to a depth of 35 km, with a transition zone extending down to 55 km depth. The slip rate in that zone increases linearly from zero to the plate convergence rate. South of the gap, the interferometric map shows interseismic deformation superimposed with deformation following the 1995 earthquake and covering the same area as the coseismic deformation. Some 40 per cent of this deformation is related to seismic activity in the 3.3 yr following the 1995 event, in particular slip during a Mw = 7.1 earthquake in 1998. However, most of the signal (60 per cent) corresponds to post-seismic deformation resulting from widespread aseismic slip in the subduction interface. The afterslip appears to have occurred down-dip in the transition zone at 35-55 km depth and to have propagated laterally northwards at 25-45 km depth under the Mejillones Peninsula, which is a prominent geomorphological feature at the boundary between the 1877 and 1995 rupture zones. We propose a simple slip model for the seismic cycle associated with the Antofagasta earthquake, where the transition zone alternates between aseismic shear and seismic slip.
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2004GeoJI.158.695C&db_key=AST

Clifton, A. E., F. Sigmundsson, K. Feigl, G. Guðmundsson, and T. Árnadóttir (2001), Surface effects of faulting and deformation resulting from magma accumulation at the Hengill triple junction, SW Iceland, 1994 - 1998, Journal of Volcanology and Geothermal Research, 115, 233-255. The Hengill triple junction, SW Iceland, is subjected to both tectonic extension and shear, causing seismicity related to strike-slip and normal faulting. Between 1994 and 1998, the area experienced episodic swarms of enhanced seismicity culminating in a ML=5.1 earthquake on June 4, 1998 and a ML=5 earthquake on November 13, 1998. Geodetic measurements, using Global Positioning System (GPS), leveling and Synthetic Aperture Radar Interferometry (InSAR) detected maximum uplift of 2 cm/yr and expansion between the Hrómundartindur and Grensdalur volcanic systems. A number of faults in the area generated meter-scale surface breaks. Geographic Information System (GIS) software has been used to integrate structural, field and geophysical data to determine how the crust failed, and to evaluate how much of the recent activity focused on zones of pre-existing weaknesses in the crust. Field data show that most surface effects can be attributed to the June 4, 1998 earthquake and have occurred along or adjacent to old faults. Surface effects consist of open gashes in soil, shattering of lava flows, rockfall along scarps and within old fractures, loosened push-up structures and landslides. Seismicity in 1994¯1998 was distributed asymmetrically about the center of uplift, with larger events migrating toward the main fault of the June 4, 1998 earthquake. Surface effects are most extensive in the area of greatest structural complexity, where N- and E-trending structures related to the transform boundary intersect NE-trending structures related to the rift zone. InSAR, GPS, and field observations have been used in an attempt to constrain slip along the trace of the fault that failed on June 4, 1998. Geophysical and field data are consistent with an interpretation of distributed slip along a segmented right-lateral strike-slip fault, with slip decreasing southward along the fault plane. We suggest a right step or right bend between fault segments to explain local deformation near the fault.

Dalfsen, E. d. Z.-v., R. Pedersen, F. Sigmundsson, and C. Pagli (2004), Satellite radar interferometry 1993–1999 suggests deep accumulation of magma near the crust-mantle boundary at the Krafla volcanic system, Iceland, Geophys. Res. Lett., 31, 1-5. Deep magma accumulation near the crust-mantle boundary (21 km depth) at the Krafla volcanic system is suggested from InSAR observations. A best fit model, derived from four interferograms covering 1993–1999, comprises an opening dike, representing plate spreading and post-rifting deformation, and two Mogi sources. A Mogi source deflating at a rate of 10^6 m^3 /yr coincides with the shallow Krafla magma chamber while a deeper inflating Mogi source, further north, at 21 km depth, inflates at a rate of 26 x 10^6 m 3 /yr. The inflating source is at or near the crust-mantle boundary as identified by seismic studies and is interpreted as accumulating magma. L13611

Delacourt, C., C. Squarzoni, and P. Allemand, One day slope motion in the Mercantour Massif (France) revealed by D-INSAR, Geophys. Res. Lett., submitted, 2000.

Delacourt, C., P. Allemand, B. Casson, and H. Vadon (2004), Velocity field of the ``La Clapière'' landslide measured by the correlation of aerial and QuickBird satellite images, Geophysical Research Letters, 31, 15619. Two displacement maps of the ``La Clapière'' landslide (France) have been derived over two periods of 4 years (1995-1999 and 1999-2003) by correlation of aerial photographs and a QuickBird satellite image. The movement of the landslide ranges from 2.5 m to 20 m per year. Those values have been validated over 13 points monitored by conventional tacheometric measurements. Three areas with significant differences in velocity field have been mapped. Limits of those areas are in good agreement with in situ observations. Velocity maps show the low long term temporal variability of the landslide movement and its spatial variability. The optical correlation method using images derived from various sensors (airborne and spatial) is a promising technique for improving the spatial resolution of velocity field observation of landslides over several years. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2004GeoRL.3115619D&db_key=AST&high=42fb8ddbb622015

Delouis, B., B. Giardini, P. Lundgren, and J. Salichon, Joint inversion of INSAR, teleseismic, and strong motion data for the spatial and temporal distribution of earthquake slip: application to the Izmit mainshock, Bull. Seism. Soc. Amer., submitted, 2001.

Emardson, T. R., M. Simons, and F. H. Webb (2003), Neutral atmospheric delay in interferometric synthetic aperture radar applications: Statistical description and mitigation, Journal of Geophysical Research (Solid Earth), 108e. Variations in the refractive index of the atmosphere cause variations in satellite-based interferometric synthetic aperture radar (InSAR) observations. We can mitigate tropospheric effects by averaging N-independent interferograms. Because the neutral atmosphere is uncorrelated at timescales longer than 1 day, using this technique statistically reduces the variance, sigma 2, of the noise by a factor of N. Using zenith neutral atmospheric delays from Global Positioning System (GPS) data from the Southern California Integrated GPS Network, we find that the average variance depends on the distance between observations, L, and height difference, H, as sigma = c L alpha + kH with estimated values for c, alpha, and k of about 2.5, 0.5, and 4.8, respectively, where sigma is in mm and L and H are in km. We expect that the value of alpha is largely site-independent but the value of c will depend on the water vapor variability of the area of interest. This model is valid over a range of L between approximately 10 and 800 km. Height differences between 0 and 3 km have been used in this analysis. For distances of 100 and 10 km with negligible height differences, sigma is estimated to be approximately 25 and 8 mm, respectively. For a given orbit revisit time and image archive duration, we calculate the number and duration (assumed constant) of interferograms required to achieve a desired sensitivity to deformation rate at a given length scale. Assuming neutral atmosphere is the dominant source of noise, a 30° look angle, and an image revisit time of 7 days, detection of a deformation rate of 1 mm yr -1 over distances of 10 km requires about 2.2 years of continuous observations. Given our results, we suggest a data covariance structure to use when using InSAR data to constrain geophysical models.
http://adsabs.harvard.edu/cgi-bin/nphbib_query?bibcode=2003JGRB.108e.ETG4E&db_key=PHY&high=42760a9e8807230

Emardson, T. R., M. Simons, and F. H. Webb (2003), Neutral atmospheric delay in interferometric synthetic aperture radar applications: Statistical description and mitigation, Journal of Geophysical Research (Solid Earth), 108e. Variations in the refractive index of the atmosphere cause variations in satellite-based interferometric synthetic aperture radar (InSAR) observations. We can mitigate tropospheric effects by averaging N-independent interferograms. Because the neutral atmosphere is uncorrelated at timescales longer than 1 day, using this technique statistically reduces the variance, sigma^2 , of the noise by a factor of N. Using zenith neutral atmospheric delays from Global Positioning System (GPS) data from the Southern California Integrated GPS Network, we find that the average variance depends on the distance between observations, L, and height difference, H, as sigma = c L^alpha + kH with estimated values for c, alpha, and k of about 2.5, 0.5, and 4.8, respectively, where sigma is in mm and L and H are in km. We expect that the value of alpha is largely site-independent but the value of c will depend on the water vapor variability of the area of interest. This model is valid over a range of L between approximately 10 and 800 km. Height differences between 0 and 3 km have been used in this analysis. For distances of 100 and 10 km with negligible height differences, sigma is estimated to be approximately 25 and 8 mm, respectively. For a given orbit revisit time and image archive duration, we calculate the number and duration (assumed constant) of interferograms required to achieve a desired sensitivity to deformation rate at a given length scale. Assuming neutral atmosphere is the dominant source of noise, a 30° look angle, and an image revisit time of 7 days, detection of a deformation rate of 1 mm yr^-1 over distances of 10 km requires about 2.2 years of continuous observations. Given our results, we suggest a data covariance structure to use when using InSAR data to constrain geophysical models.

http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003JGRB.108e.ETG4E&db_key=PHY&high=42fb8ddbb619944

Feigl, K. L., F. Sarti, H. Vadon, P. Durand, S. McClusky, S. Ergintav, R. Bürgmann, A. Rigo, D. Massonnet, and R. Reilinger (2002), Estimating slip distribution for the Izmit mainshock from coseismic GPS, ERS-1, RADARSAT and SPOT measurements, Bull. Seism. Soc. Amer., 92, 138-160. We use four geodetic satellite systems (GPS, ERS, RADARSAT, and SPOT) to measure the permanent deformation field produced by the Izmit earthquake of August 17, 1999. The emphasis is on measurements from interferometric analysis of synthetic aperture radar (INSAR) images acquired by ERS and RADARSAT and their geodetic uncertainties. The primary seismological use of these data is to determine earthquake source parameters, such as the distribution of slip and the fault geometry. After accounting for a month's post-seismic deformation, tropospheric delay, and orbital gradients, we use these data to estimate the distribution of slip at the time of the Izmit mainshock. The different data sets resolve different aspects of the distribution of slip at depth. Although these estimates agree to first order with those derived from surface faulting, teleseismic recordings, and strong motion, careful comparison reveals differences of 40% in seismic moment. We assume smooth parameterization for the fault geometry and a standard elastic dislocation model. The RMS residual scatter is 25 mm and 11 mm for the ERS and RADARSAT range changes, respectively. Our estimate of the moment from a joint inversion of the four geodetic data sets is M0 = 1.84E20 N.m, a moment magnitude of Mw = 7.50. These values are lower than other estimates using more realistic layered earth models. Given the differences between the various models, we conclude that the real errors in the estimated slip distributions are at the level of 1 meter. The prudent geophysical conclusion is that co-seismic slip during the Izmit earthquake tapers gradually from approximately 2 m under the Hersek Delta to 1 m at a point 10 km west of it. We infer that the Yalova segment west of the Hersek Delta may remain capable of significant slip in a future earthquake.