Measuring the deformation at the Earth’s surface over a range of spatial and temporal scales is vital for understanding seismic hazard, detecting volcanic unrest and assessing the effects of vertical land movements on sea level rise. Here, we combine ~10 years of InSAR observations from Envisat with interseismic campaign and continuous GNSS velocities to build a high-resolution velocity field of New Zealand. Exploiting the horizontal GNSS observations, we estimate the vertical component of the deformation to provide the vertical land movement (VLM) for the entire 15,000 km-long coastline. The estimated vertical rates show large variability around the country as a result of volcanic, tectonic and anthropogenic sources. Interseismic subsidence is observed in Kaikoura region supporting models of at least partial locking of the southern Hikurangi subduction interface. Despite data challenges in the mountainous regions from landslides, sediment compaction and glaciers, InSAR data shows localised uplift of the Southern Alps.

The launches of the Sentinel-1 synthetic aperture radar satellites in 2014 and 2016 started a new era of high-resolution velocity and strain rate mapping for the continents. However, multiple challenges exist in tying independently processed velocity data sets to a common reference frame and producing high-resolution strain rate fields. We analyse Sentinel-1 data acquired between 2014 and 2019 over the northeast Tibetan Plateau, and develop new methods to derive east and vertical velocities with ~100 m resolution and ~1 mm/yr accuracy across an area of 440,000 km^2. By implementing a new method of combining horizontal gradients of filtered east and interpolated north velocities, we derive the first ~1 km resolution strain rate field for this tectonically active region. The strain rate fields show concentrated shear strain along the Haiyuan and East Kunlun Faults, and local contractional strain on fault junctions, within the Qilianshan thrusts, and around the Longyangxia Reservoir. The Laohushan-Jingtai creeping section of the Haiyuan Fault is highlighted in our data set by extremely rapid strain rates. Strain across unknown portions of the Haiyuan Fault system, including shear on the eastern extension of the Dabanshan Fault and contraction at the western flank of the Quwushan, highlight unmapped tectonic structures. In addition to the uplift across most of the lowlands, the vertical velocities also contain climatic, hydrological or anthropogenic-related deformation signals. We demonstrate the enhanced view of large-scale active tectonic processes provided by high-resolution velocities and strain rates derived from Sentinel-1 data and highlight associated wide-ranging research applications.

Satellite radar backscatter has the potential to provide useful information about the progression of volcanic eruptions when optical, ground-based, or radar phase-based measurements are limited. However, backscatter changes are complex and challenging to interpret: explosive deposits produce different signals depending on pre-existing ground cover, radar parameters and eruption characteristics. We use high temporal- and spatial-resolution backscatter imagery to examine the emplacement and alteration of pyroclastic flows, lahars, and ash from the June 2018 eruption of Volcan de Fuego, Guatemala, drawing on observatory reports and rain gauge data to ground truth our observations. We use dense timeseries of backscatter to reduce noise and extract deposit areas. Backscatter decreases where six flows were emplaced on 3 June 2018. In Barranca Las Lajas, we measured a 11.9-km-long flow that altered an area of 6.3 km2; and used radar shadows to estimate a thickness of 10.5 +/- 2 m in the lower sections. The 3 June eruption also changed backscatter over an area of 40 km2, consistent with ashfall. We use transient patterns in backscatter timeseries to identify nine periods of high lahar activity in B. Las Lajas between June and October 2018. We find that the characterisation of subtle backscatter signals associated with explosive eruptions is assisted by (1) radiometric terrain calibration, (2) speckle correction, and (3) consideration of pre-existing scattering properties. Our observations demonstrate that SAR backscatter can capture both the emplacement and subsequent alteration of a range of explosive products, allowing the progression of an explosive eruption to be monitored.

Processes that facilitate the transition between continental rifting and sea-floor spreading remain unclear. Variations in the spatial distribution of extension through Afar and into the Red Sea are indicative of temporal evolution of the rift. We develop a time series of Sentinel-1 interferometric synthetic aperture radar (InSAR) observations of ground deformation covering the whole Afar Rift from 2014-2019, to study the distribution of extension across all magmatic segments. By incorporating GNSS observations, we resolve 3D average velocities in the vertical, rift-perpendicular, and rift-parallel directions. Results show the spatial distribution of long-term plate motions over the rift, as well as deformation at individual volcanic centres, including Dallol, Nabro, and Erta ’Ale. We find that in northern and central Afar, the majority of extension is accommodated within +/- 15-30 km of magmatic spreading centres. In southern Afar, near the Nubia-Arabia-Somalia triple-junction, extension is distributed over 90-180 km, which may indicate an increase in rift focussing with rift maturity. We also observe rapid surface uplift and rift-perpendicular extension at the Dabbahu-Manda-Hararo segment with velocities of 33 +/- 4 mm/yr and 37 +/- 4 mm/yr respectively. These are higher than the background extension rate of 18-20 mm/yr, but have decreased by 55-70 % since 2006-10. The data suggests that this is due to an on-going long-lived response to the 2005-10 rifting episode, with potential continued processes below the segment including a lower-crustal viscous response and magma movement. Continued long-term observations of surface deformation provide key constraints on tectono-magmatic processes in Afar.