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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 (VLMs) on sea level rise. Here, we combine ∼10 years of Interferometric Synthetic Aperture Radar (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 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 localized uplift of the Southern Alps. Plain Language Summary: Interferometric Synthetic Aperture Radar (InSAR) data provides a method to measure the deformation of the Earth's surface at high spatial resolutions over large geographic footprints. Here we exploit historical SAR and GNSS data acquired over New Zealand between 2003 and 2011 to measure the nationwide surface velocities. With the combination of GNSS and InSAR data, we are able to estimate the vertical deformation for the entire country and provide a first estimate of the coastal vertical land movements which are a key data set for future projections of sea level rise. As a result of New Zealand's dynamic tectonic setting, there is large temporal and spatial variability around the country as a result of volcanic, tectonic, and anthropogenic processes. Key Points: Using Envisat InSAR and GNSS data, we derive a velocity field derived for New ZealandCombining InSAR and GNSS enables us to provide a nationwide estimate of the vertical deformation field for the first timeEstimated vertical rates show large variability around the country as a result of volcanic, tectonic, and anthropogenic sources [ABSTRACT FROM AUTHOR]

Launched in 2015, the New Zealand volcano supersite provides regular radar acquisitions covering all the major calderas and cone volcanoes which form the Taupō Volcanic Zone (TVZ). This paper documents new InSAR (Interferometric Synthetic Aperture Radar) observation of deformation over the cone volcanoes within the TVZ including the Tongariro Volcanic complex (TVC) and White Island. Observations over White Island support earlier observations indicating that the stability of the crater wall is controlled, at least in part, by the water level in the crater lake with downslope motion of ∼50 mm/yr observed during the latest period of lake drop in early 2019. Deformation over the TVC is dominated by the continued subsidence above the 2012 Te Maari eruption site at rates of ∼30 mm/yr with no evidence of deformation elsewhere. Synthetic models, used to test the potential detectability of magma movement beneath Ruapehu and White Island, suggest that for small volumes (<0.005–0.02 km3), intruded over short periods of time, it would be difficult for InSAR data alone to identify their accumulation. These challenges are not unique to New Zealand's volcanoes and are likely to be faced at other volcanic systems globally. [ABSTRACT FROM AUTHOR]

The 14th November 2016 Kaikōura earthquake was one of the most complex crustal earthquakes recorded in the modern era. The rupture propagated northward for more than 170 km along both mapped and unmapped faults causing widespread damage across central New Zealand. Field, Satellite Radar and GPS observations revealed ground displacements of up to 6 m (fault offsets of ∼12 m), extensive coastal uplift and large scale anelastic deformation including the ∼10 m uplift of a fault-bounded block.In the aftermath of the earthquake, slip models have estimated as much as 25 m of slip at depth along with the potential co-seismic rupture of the southern Hikurangi subduction interface. From the complex network of faults, exhibiting a variety of slip kinematics, to the large co-seismic slip, this earthquake has challenged our assumptions about fault segmentation in multi fault ruptures with important implications for seismic hazard. Following the earthquake, studies from multiple national and international groups have started to unravel some of the earthquakes complexities. Here I will present a broad overview of the current findings and discuss some of the ongoing debates and questions which have yet to be resolved. [ABSTRACT FROM AUTHOR]

In late 2018, Ambrym volcano, Vanuatu, erupted for the first time in 3 years. We show that the eruption was the result of a 6.5‐m‐wide, ∼0.7‐km3 dike intrusion which propagated for more than 20 km into the eastern rift zone. The eruptive sequence began with a small shallow dike within the main caldera but ultimately triggered a much larger intrusion, draining both the shallow (1–2 km) and deeper (∼5 km) magmatic systems. Extension of ∼3 m is estimated across the eastern rift zone with more than 2 m of subsidence within the caldera. Modeling suggests that the stress changes induced by the initial dike emplacement helped trigger and guide the propagation of the flank intrusion. Despite the large volume of material removed from beneath the caldera (∼0.7 km3), limited slip is observed along bounding faults supporting the hypothesis that the long‐term formation of the caldera at Ambrym is a result of repeated moderate‐sized events. Key Points: The 2018 eruption at Ambrym was associated with more than 2 m of caldera subsidence and the intrusion of a ∼26‐km‐long dikeTo explain the complex deformation pattern requires that the intrusion was fed by multiple magma sources beneath the calderaComparison between slip along caldera faults and eruption volume suggests Ambrym's caldera forms through repeated moderate‐sized eruptions [ABSTRACT FROM AUTHOR]

Many volcanoes around the world host summit crater lakes but their influence on the overall stability of the edifice remains poorly understood. Here I use satellite radar data acquired by TerraSAR-X from early 2015 to July 2017 over White Island, New Zealand, to investigate the interaction of the crater lake and deformation of the surrounding edifice. An eruption in April 2016 was preceded by a period of uplift within the crater floor and drop in the lake level. Modeling of the uplift indicates a shallow source located at ∼100 m depth in the vicinity of the crater lake, likely coinciding with the shallow hydrothermal system. In addition to the drop in the lake level, stress changes induced by the inflation suggest that the pressurization of the shallow hydrothermal system helped promote failure along the edge of the crater lake which collapsed during the eruption. After the eruption, and almost complete removal of the crater lake, large areas of the crater wall and lake edge began moving downslope at rates approaching 400 mm/yr. The coincidence between the rapid increase in the displacement rates and removal of the crater lake suggests that the lake provides a physical control on the stability of the surrounding edifice. [ABSTRACT FROM AUTHOR]

In this paper we examine a short‐lived aseismic slip episode which began immediately following the 2016 Kaikōura earthquake in the South Island of New Zealand. Using synthetic aperture radar data, we form an interferometric synthetic aperture radar time series over the epicentral region of the Kaikōura mainshock. Immediately following the earthquake, we observe 150 mm of localized uplift over an ∼25‐km2 region which is best explained by an increase in pore pressure within a shallow fluid trap as a result of a coseismic permeability change. After the initial uplift stops, deformation becomes focused along a NE‐SW trending discontinuity which cuts through the uplifted region. The fault lies within a large (∼−4 MPa) stress shadow induced by the coseismic stress change suggesting that failure should be inhibited. However, a reduction in the effective normal stress caused by the local pore pressure increase was sufficient to induce a short‐lived aseismic slip episode. Plain Language Summary: Pore fluid pressure plays a critical role in fault behavior. As the pressure increases, the stresses which help prevent the fault from breaking are reduced making it easier for the fault to move. In this study, we use interferometric synthetic aperture radar data to measure an aseismic slip (no earthquakes) episode within the epicentral region of the 2016 Kaikoura earthquake in New Zealand. Localized uplift observed immediately after the earthquake was likely caused by a pore pressure increase within a shallow fluid trap as a result of a coseismic permeability change. The observed uplift rapidly dissipates with displacements becoming focused along a NE‐SW trending fault. Because of the position and orientation of the fault relative to the Kaikoura rupture, slip along the fault would have been inhibited by the Kaikoura stress change. However, because of the local increase in pore pressure, the fault was able to move over a period of a few weeks without generating detectable seismic energy until the pore pressure dissipated and the fault relocked. Based on these observations and scaled to larger displacement episodes, along‐strike variations in fluid budget could explain the changes in fault behavior observed along larger fault systems. Key Points: Localized postseismic uplift was induced by pressurized fluids within shallow trapLarge increase in pore pressure was sufficient to trigger an aseismic slip episodeRapid relocking of the fault is consistent with pore fluid diffusion [ABSTRACT FROM AUTHOR]

The country of El Salvador, located at the convergent boundary of the Cocos and Caribbean plates, is subject to frequent seismic events and complex surface deformation. This paper presents the first Interferometric Synthetic Aperture Radar (InSAR)-based velocity field of El Salvador produced by combining InSAR and new GNSS data, which allows us to gain a deeper understanding of the intricate crustal deformation processes in the region. We use L-Band ALOS PALSAR images from five ascending and two descending tracks, as well as 171 continuous and episodic GNSS stations across El Salvador and the Caribbean. The inversion of GNSS and InSAR velocities along fault-perpendicular profiles enable us to assess the accommodation of tectonic deformation along the El Salvador Fault Zone (ESFZ), providing a better constraint on the behaviour of its main structures. Additionally, we are able to better understand how the deformation is transmitted at the western (Jalpatagua-Ipala) and eastern (Fonseca Gulf) terminations of the ESFZ. • We obtain the first continuous velocity field in El Salvador derived from InSAR data. • The El Salvador Fault Zone is coupled and the forearc is faster towards the west. • West of El Salvador, the deformation is distributed, coherently with a closing zipper. [ABSTRACT FROM AUTHOR]