Active tectonics

Crustal earthquakes and the seismic cycle

I am interested in the use of InSAR to study active crustal deformation produced by both tectonic and volcano-tectonic processes. Geodetic data can provides critical information not available by point source seismic inversions like the complexity of fault slip in the Earth’s surface, evidence for complex rupture geometries and the role of magmatic fluids in aseismic deformation. InSAR also provides insights on large scale mechanisms of deformation across orogens.

Interferograms that span the seismic cyle of the Pichilemu fault (black lines) in Central Chile. This fault ruptured in two Mw 7.0 eqarthquakes triggered by the Mw 8.8 Maule megathrust earthquake in 2010. Thr first interferogram shows no interseismic strain accumulation three years before the earthquake, the second and third interferograms show the coseismic rupture imaged by L-band ALOS and C-band ENVISAT data, and the last two interferograms show stress-driven afterslip triggered by the coseismic rupture during a time span of 3 months.

Sentinel-1 interferogram of the January 2021 Mw 6.4 San Juan earthquake (seismic epicenter is the grey square, and focal mechanism is from GCMT), and time series of cumulative deformation (bottom). This earthquake is the largest in the era of InSAR geodesy along the Andean fold and thrut belt, and can only be imaged with InSAR with a Heaviside fit to the time series or from winter to winter interferogram. Phase delays are very strong in 12 day pairs (Delgado et al., 2024, León-Ibañez and Delgado, submitted).

TerraSAR-X wrapped (a) and unwrapped (b) interferogram of the July 17 2013 Mw 5.9 earthquake in the Mojopampa normal fault NW of Sabancaya volcano (black triangle) in Southern Peru. The geodetic focal mechanism is in agreement with the seismic moment tensor, showing that there is no evidence for fluid-driven deformation (Jay, Delgado et al., 2015). Wrapped (c) and unwrapped (d) TerraSAR-X mean velocity calculated from InSAR time series from November 2013 to December 2016 showing ~4-5 cm of uplift produced by a deep inflating source beneath Hualca Hualca volcano. The inflation likely triggers aseismic afterslip in the Mojopampa fault, which is better observed in the wrapped interferogram (Macqueen, Delgado et al., 2020).

Strike slip faults

Fence displaced ~6 m by the 1949 Mw ~7.2 sinistral doublet in the Magallanes Fagnano fault, Tierra del Fuego.

12 m shaded relief TanDEM-X DEM of spanning the Magallanes Fagnano fault. The red arrows show a ~25 km long segment of the 1949 rupture.

Time series of eastward displacement recorded by two GNSS stations located 7.5 km north and south from the Magallanes Fagnano fault. The difference of 2 mm/yr in the mean velocity between the two stations is due to the shallow coupling of the fault.

Relevant publications

León-Ibañez, P., Delgado, F. Resolving ground deformation of a blind mid-crustal earthquake with InSAR amid strong phase delays: a case study of the 2021 Mw 6.4 San Juán earthquake (Andean Fold and Thrust Belt, Argentina). Geophysical Research Letters, submitted.

A global assessment of SAOCOM-1 L-band stripmap data for InSAR characterization of volcanic, tectonic, cryospheric, and anthropogenic deformation.
Delgado, F., Shreve, T., Borgstrom, S., León-Ibañez, P., Castillo, J., Poland, M.,2024 IEEE Transactions on Geoscience and Remote Sensing, doi:10.1109/TGRS.2024.3423792.

Fully joint inversion of the 2016 Mw 7.6 Chiloé earthquake.
Bravo, F., Peyrat, S., Delgado, F., Fuentes, M., Derode, B., Pérez, A., Campos, J., Geophysical Journal International, 2023, 232, 3, 2001–2016, doi:10.1093/gji/ggac411

Volcano-tectonic interactions at Sabancaya volcano, Peru: eruptions, magmatic inflation, moderate earthquakes, and fault creep
MacQueen, P., Delgado, F., Reath, K., Pritchard, M., Lundgren, P., Milillo, P., Bagnardi, M., Macedo, O., Aguilar, V., Lazarte, I., Machacca, R., Miranda, R. Journal of Geophysical Research. 2020, doi.org/10.1029/2019JB019281. Special issue on Creep on continental faults and subduction zones: Geophysics, geology, and mechanics.

Deformation and seismicity near Sabancaya volcano, southern Peru, from 2002 to 2015
Jay, J.A., Delgado, F.J., Torres, J.L., Pritchard, M.E., Macedo, O., Aguilar , V. Geophys. Res. Lett.. 2015, 42, 2780–2788. doi: 10.1002/2015GL063589.