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Faults present potential leakage risks for geological CO2 storage. To de‐risk a field test injecting CO2 into a shallow fault, laboratory sand tank fluid flow experiments were conducted prior to field injection. The vertical 2.5D sand tank analog models were constructed with different grain sizes of glass beads to represent the permeability contrast between formation layers. A variety of analog fluids were also used to represent both the injection of gaseous and supercritical CO2. Experimental results have validated the simulation results in terms of fluid migration pathways. In addition, results with different analog fluids show that CO2 migration along faults is likely to have similar overall flow paths both near the surface and at depth, but different plume sizes and saturation. Finally, based on an inspectional scaling analysis, we were able to estimate field‐scale CO2 plume migration time, which has been validated by real field observations for the first time. Plain Language Summary Ensuring the safety and security of geological CO2 storage projects is critical. Geological faults can be potential leakage pathways if the fault is not fully sealed to fluid flow. To better understand how CO2 would behave in the unlikely case it leaks through a fault, we built physical models using different sized glass beads and used various fluids to mimic the properties of CO2 and brine at reservoir conditions. These sand tank experiments were modeled after a field site at the Otway International Test Center, where CO2 was injected into a shallow fault. Results obtained from the laboratory experiments were then compared with both reservoir simulation and subsequent field test results. There was a good match between the sand tank results and field experiment. This study demonstrates how sand tank experiments can be used to yield useful insights into CO2 flow at geological faults. Key Points Laboratory sand tank fluid flow experiments were conducted to compare to both simulation and field results Different analog fluids were used to model CO2 injection through an open fault at both shallow and deep depths Experimental results were able to match field plume breakthrough time using inspectional scaling analysis

Treatment wetlands are recognized as an effective technology for mitigating the impacts of urban runoff. However, there is no consensus on the design guidelines, and the effects of some design features, such as the underdrain system, remain unexplored. A simple analog model has been developed to mimic the underdrain network (when operating at saturation) and to evaluate the spatial heterogeneity of the flow entering it. The model has been applied to a treatment wetland in the Paris area and shows that the underdrain network was largely undersized, likely causing an uneven distribution of infiltrating flow along the length of the treatment wetland. It was also shown that this analog model can be used for optimization purposes and that it is important to use conservative values of the rugosity coefficient when designing an underdrain network.

Bentarsari sub-watershed is located at Brebes Regency administrative area, Central Java. This sub-watershed is surrounded by hills composed by volcanic breccia of Kumbang Formation (Tpk) and consists of sedimentary rocks at the lower part of the watershed. Volcanic breccia is the oldest rock in the watershed and appears to have a more intensive weathering process, making it more susceptible to landslides which are mostly followed by debris flow. Accordingly, the aim of this research is to conduct a laboratory scale analog modeling of debris flow event in this sub-watershed. The main materials used for modeling are moderate to completely weathered volcanic breccias to residual soils. The rainfall scenario is 50 mm/day as lower bound of heavy rain, 100 mm/day as lower bound of very heavy rain and 150 mm/day as lower bound of extreme rain. As a first step, the computer simulation is used for analyzing material movement of the model, using spherical materials with a density of 1.84 g/cm 3 taken from average value of laboratory test results. The simplification process is carried out on spherical material with 4 cm and 2 cm diameter to depict moving material. The solid material volume used in the simulation is 0.07 m 3 while the liquid is 0.03 m 3 . Then, a laboratory scale analog model has been made with a tub having dimensions of 0.5 m high, 2 m long and 1 m wide. When this analog model is tilted 50 degrees, the resulting slip plane then extends to the backward of the slope and the flowing materials move downward colliding with the previously deposited material, forming a flow which bends slightly to the left at the foot slope. The results of this research are expected to lead to a new method for modelling debris flows using analog models at laboratory scale.

Characterisation of surface deformation at stratovolcanoes is essential for a better understanding of the processes that can compromise edifice structural stability and potential for flank collapse. Spreading produced by the presence of a hydrothermal system or intrusion of a viscous magma body can produce similar deformation signatures, and both processes have implications for flank instability. In this work, we perform analogue models and consider examples from real volcanoes (Damavand, Ubinas, Semeru and Casita) so as to characterise and recognise surface deformation patterns produced by spreading due to the presence of a hydrothermal system and in response to magma intrusion. The experiments show that there are differences in the resulting surface deformation associated with each process. Magma intrusion results in a sharp transition between areas of subsidence and uplift, and is associated with faults with oblique strikes in the upper part of the edifice. Instead, asymmetric flank spreading is associated with hydrothermal system and results in flank bulging close to the base of the edifice. Although laboratory analogue models show different deformation responses that could be diagnostic of the associated processes, application in the field is difficult as often these diagnostic features are not preserved during evolution. However, basal bulging represents a potential diagnostic for the identification of asymmetric volcano flank spreading associated with hydrothermal activity, and the potential for instability. Remote sensing techniques can allow identification of such surface deformation features, providing a useful tool for hazard assessment and design of monitoring strategies at potentially unstable volcanoes.

In the Western Alps, a first Late Cretaceous to Eocene \"Pyrenean-Provençal\" compressive phase accommodating N-S shortening resulting from the convergence between Africa and Eurasia is classically described. It is followed by the Neogene \"Alpine phase\" accommodating E-W shortening. Since this major tectonic change is not explained by a modification of the global Africa-Eurasia convergence, it should be explained instead by more local causes, possibly by the subduction of the Ligurian Ocean that initiated in the Oligocene beneath the European and Iberian plates. In this paper, we present analogue models simulating the Neogene evolution of this subduction zone, in order to understand how it impacted the regional tectonics. Although models do not include the lithospheric plate overriding the subduction zone, their surface deformations share many similarities with the Neogene tectonics of Western Europe and Iberia. We observe that the tectonic evolution is largely controlled by the roll-back of the slab, that occurred much faster than the Africa-Eurasia convergence. Models reproduce the opening of the Western Mediterranean Basins and the dispersion of the AlKaPeCa continental fragments (Alboran, Kabylian, Peloritan and Calabrian blocks). They also show that the subduction of the Ligurian Ocean favors the counterclockwise rotation of Adria. In more elaborated models, we introduced a pre-existing weakness along the Africa and Adria margins, to reproduce the break-off of the oceanic slab that followed the beginning of continental subduction both in Northern Africa and Adria. Slab break-off is followed by the exhumation of the subducted continent. We observe that the influence of subduction on the kinematics of Adria largely decreases following slab break-off. In the models, the total counterclockwise rotation of Adria varies between 7° and more than 30°, depending on the timing of slab break-off. Since the process of subduction modifies the displacement of Adria, it also impacts the tectonic evolution of surrounding regions, especially in the Alpine belt: Our models show that during slab-roll back and before the Ligurian slab break-off, the azimuth of convergence between Adria and Europe shifts from ∼N-S to ∼ENE-WSW. Hence, they suggest that the oceanic subduction in the Western Mediterranean may contribute to the \"Oligocene revolution\" described by Dumont et al. (2011), leading to E-W shortening in the Western Alps and to the activation of the Periadriatic right-lateral shear zones in the Central Alps. We conclude that the western Mediterranean region is a spectacular example showing how the tectonics of mountain ranges and plate boundaries may be controlled by distant subduction processes.

The Higher Himalayan Shear Zone (HHSZ) contains a ductile top-to-N/NE shear zone—the South Tibetan detachment system-lower (STDS L ) and an out-of-sequence thrust (OOST) as well as a top-to-N/NE normal shear at its northern boundary and ubiquitously distributed compressional top-to-S/SW shear throughout the shear zone. The OOST that was active between 22 Ma and the Holocene, varies in thickness from 50 m to 6 km and in throw from 1.4 to 20 km. Channel flow analogue models of this structural geology were performed in this work. A Newtonian viscous polymer (PDMS) was pushed through a horizontal channel leading to an inclined channel with parallel and upward-diverging boundaries analogous to the HHSZ and allowed to extrude to the free surface. A top-to-N/NE shear zone equivalent to the STDS U developed spontaneously. This also indirectly connotes an independent flow confined to the southern part of the HHSZ gave rise to the STDS L . The PDMS originally inside the horizontal channel extruded at a faster rate through the upper part of the inclined channel. The lower boundary of this faster PDMS defined the OOST. The model OOST originated at the corner and reached the vent at positions similar to the natural prototype some time after the channel flow began. The genesis of the OOST seems to be unrelated to any rheologic contrast or climatic effects. Profound variations in the flow parameters along the HHSZ and the extrusive force probably resulted in variations in the timing, location, thickness and slip parameters of the OOST. Variation in pressure gradient within the model horizontal channel, however, could not be matched with the natural prototype. Channel flow alone presumably did not result in southward propagation of deformation in the Himalaya.

Convergent margins with oblique subduction commonly include a fore‐arc sliver, a portion of the overlying plate bounded by the trench and a major strike‐slip fault system. It has long been noted that relative plate motion near the deformation front, as indicated by earthquake focal mechanisms, is generally closer to margin‐normal than would be expected from overall relative plate motion. This results from sliver motion as well as from shear within the fore arc. We carry out some simple calculations to determine how the rate of sliver motion should vary with plate convergence obliquity. We find that the results are related to rheology but that the measurement of sliver rates at natural fore arcs is unlikely to yield real insight into physical properties; even for very simple models; the system is too complicated and its relation to rheology is not unique. The proportion of oblique convergence taken up by sliver motion in simple tabletop experiments depends on the rate of slip and the smoothing of asperities. Similarities in taper and style of strain between frontal wedges forming with and without slivers suggest that structural observations of exhumed accretionary wedges are unlikely to allow geologists to draw definitive conclusions about the degree of obliquity of relative plate motion at the time when the wedges were formed and in some cases not even whether or not a sliver plate was present at the time of deformation.

Planets form in the disks around young stars. Their formation efficiency and composition are intimately linked to the protoplanetary disk locations of \"snow lines\" of abundant volatiles. We present chemical imaging of the carbon monoxide (CO) snow line in the disk around TW Hya, an analog of the solar nebula, using high spatial and spectral resolution Atacama Large Millimeter/Submillimeter Array observations of diazenylium (N 2 H + ), a reactive ion present in large abundance only where CO is frozen out. The N 2 H + emission is distributed in a large ring, with an inner radius that matches CO snow line model predictions. The extracted CO snow line radius of ∼30 astronomical units helps to assess models of the formation dynamics of the solar system, when combined with measurements of the bulk composition of planets and comets.

Analogue models of (and for) gravity have a long and distinguished history dating back to the earliest years of general relativity. In this review article we will discuss the history, aims, results, and future prospects for the various analogue models. We start the discussion by presenting a particularly simple example of an analogue model, before exploring the rich history and complex tapestry of models discussed in the literature. The last decade in particular has seen a remarkable and sustained development of analogue gravity ideas, leading to some hundreds of published articles, a workshop, two books, and this review article. Future prospects for the analogue gravity programme also look promising, both on the experimental front (where technology is rapidly advancing) and on the theoretical front (where variants of analogue models can be used as a springboard for radical attacks on the problem of quantum gravity).

The dynamics of slab detachment and associated geological fingerprints have been inferred from various numerical and analog models. These invariably use a setup with slab‐pull‐driven convergence in which a slab detaches below a mantle‐stationary trench after the arrest of plate convergence due to arrival of continental lithosphere. In contrast, geological reconstructions show that post‐detachment plate convergence is common and that trenches and sutures are rarely mantle‐stationary during detachment. Here, we identify the more realistic kinematic context of slab detachment using the example of the India‐Asia convergent system. We first show that only the India and Himalayas slabs (from India's northern margin) and the Carlsberg slab (from the western margin) unequivocally detached from Indian lithosphere. Several other slabs below the Indian Ocean do not require a Neotethyan origin and may be of Mesotethys and Paleotethys origin. Additionally, the still‐connected slabs are being dragged together with the Indian plate forward (Hindu Kush) or sideways (Burma, Chaman) through the mantle. We show that Indian slab detachment occurred at moving trenches during ongoing plate convergence, providing more realistic geodynamic conditions for use in future numerical and analog experiments. We identify that the actively detaching Hindu Kush slab is a type‐example of this setting, whilst a 25–13 Ma phase of shallow detachment of the Himalayas slab, here reconstructed from plate kinematics and tomography, agrees well with independent, published geological estimates from the Himalayas orogen of slab detachment. The Sulaiman Ranges of Pakistan may hold the geological signatures of detachment of the laterally dragged Carlsberg slab. Key Points Kinematic context of slab detachment Slab detachment during ongoing convergence