Three‐dimensional near‐fault coseismic deformation fields from high‐resolution differential topography provide new information on the behavior of the shallow fault zone in large surface‐rupturing earthquakes. Our work focuses on the 16 April 2016 Mw 7.0 Kumamoto, Japan, earthquake, which ruptured ~40 km of the Futagawa‐Hinagu Fault Zone on Kyushu Island with an oblique strike‐slip mechanism and surface offset exceeding 2 m. Our differential lidar analysis constrains the structural style of strain accommodation along the primary fault trace and the surrounding damage zone. We show that 36 ± 29% and 62 ± 32% of the horizontal and vertical deformation, respectively, was accommodated off the principal fault trace. The horizontal strains of up to 0.03 suggest that the approximate elastic strain limit was exceeded over a ~250 m width in many locations along the rupture. The inelastic deformation of the fault volume produced the observed distributed deformation at the Earth's surface. We demonstrate a novel approach for calculating 3‐D displacement uncertainties, indicating errors of centimeters to a few decimeters for displacements computed over 50 m horizontal windows. Errors correlate with land cover and relief, with flatter agricultural land associated with the highest displacement uncertainty. These advances provide a framework for future analyses of shallow earthquake behavior using differential topography.

AbstarctConstraints on soil moisture can guide agricultural practices, act as input into weather, flooding and climate models and inform water resource policies. Space-based interferometric synthetic aperture radar (InSAR) observations provide near-global coverage, even in the presence of clouds, of proxies for soil moisture derived from the amplitude and phase content of radar imagery. We describe results from a 1.5 year-long InSAR time series spanning the March, 2015 extreme precipitation event in the hyperarid Atacama desert of Chile, constraining the immediate increase in soil moisture and drying out over the following months, as well as the response to a later, smaller precipitation event. The inferred temporal evolution of soil moisture is remarkably consistent between independent, overlapping SAR tracks covering a region ~100 km in extent. The unusually large rain event, combined with the extensive spatial and temporal coverage of the SAR dataset, present an unprecedented opportunity to image the time-evolution of soil characteristics over different surface types. Constraints on the timescale of shallow water storage after precipitation events are increasingly valuable as global water resources continue to be stretched to their limits and communities continue to develop in flood-prone areas.

No abstract

Observations of surface deformation within 1–2 km of a surface rupture contain invaluable information about the coseismic behavior of the shallow crust. We investigate the oblique strike‐slip 2016 M7 Kumamoto, Japan, earthquake, which ruptured the Futagawa‐Hinagu Fault. We solve for variable fault slip in an inversion of differential lidar topography, satellite optical image correlation, and Interferometric Synthetic Aperture Radar (InSAR)‐derived surface displacements. The near‐fault differential lidar pose several challenges. The model fault geometry must follow the surface trace at the sub‐kilometer scale. Integration of displacement datasets with different sensitivities to the 3D deformation field and varying spatial distribution permits additional complexity in the inferred slip but introduces ambiguity that requires careful selection of the regularization. We infer a Mw 7.09−0.05+0.03 earthquake. The maximum slip of 6.9 m occurred at 4.5‐km depth, suggesting an on‐fault slip deficit in the upper several kilometers of the crust that likely reflects distributed and inelastic deformation within the shallow fault zone.

We calculate the daily time series for 12 continuous GPS stations that are part of the Central Andean Tectonic Observatory Geodetic Array (Simons et al., 2010) or an array operated by the Chilean government, and are all processed by Blewitt (2015). From the time series of station positions, we calculate the coseismic displacement during the April 1 M w 8.1 earthquake by subtracting the station position on March 31 from that on April 2, 2014. Likewise the April 3 M w 7.7 coseismic displacements were calculated by subtracting the position on April 2 from the position on April 4, 2014. Unfortunately station CLLA (Figure 1S) had a recording gap during the earthquakes, so the separated coseismic displacements are available for just 11 stations, but CLLA can still be used to calculate the overall strain from the entire sequence, combined. We solve for the distance-weighted infinitesimal displacement gradient tensor (Allmendinger et al., 2009; Cardozo and Allmendinger, 2009) by independently inverting the three sets of GPS displacement vectors. We test a range of distance weighting parameters from 35 to 150 km, and select the one that produces the most consistent fit between the mean crack orientations and the GPS-inferred maximum horizontal shortening axes. We find 50 km to be the optimal distance weighting parameter. Interferometric Synthetic Aperture Radar (InSAR) Methods: We generate a coseismic ascending interferogram using X-band SAR imagery with a wavelength of 3.1 cm from the TerraSAR-X satellite shown in Figure DR7. We process the

No abstract

The 2014 Mw = 8.1 Iquique (Pisagua), Chile, earthquake sequence ruptured a segment of the Nazca‐South America subduction zone that last hosted a great earthquake in 1877. The sequence opened >3700 surface cracks in the fore arc of decameter‐scale length and millimeter‐to centimeter‐scale aperture. We use the strikes of measured cracks, inferred to be perpendicular to coseismically applied tension, to estimate the slip distribution of the main shock and largest aftershock. The slip estimates are compatible with those based on seismic, geodetic, and tsunami data, indicating that geologic observations can also place quantitative constraints on rupture properties. The earthquake sequence ruptured between two asperities inferred from a regional‐scale distribution of surface cracks, interpreted to represent a modal or most common rupture scenario for the northern Chile subduction zone. We suggest that past events, including the 1877 earthquake, broke the 2014 Pisagua source area together with adjacent sections in a throughgoing rupture.

No abstract