Recent advances in unmanned-aerial-vehicle- (UAV-) based remote sensing utilizing lightweight multispectral and thermal infrared sensors allow for rapid wide-area landmine contamination detection and mapping surveys. We present results of a study focused on developing and testing an automated technique of remote landmine detection and identification of scatterable antipersonnel landmines in wide-area surveys. Our methodology is calibrated for the detection of scatterable plastic landmines which utilize a liquid explosive encapsulated in a polyethylene or plastic body in their design. We base our findings on analysis of multispectral and thermal datasets collected by an automated UAV-survey system featuring scattered PFM-1-type landmines as test objects and present results of an effort to automate landmine detection, relying on supervised learning algorithms using a Faster Regional-Convolutional Neural Network (Faster R-CNN). The RGB visible light Faster R-CNN demo yielded a 99.3% testing accuracy for a partially withheld testing set and 71.5% testing accuracy for a completely withheld testing set. Across multiple test environments, using centimeter scale accurate georeferenced datasets paired with Faster R-CNN, allowed for accurate automated detection of test PFM-1 landmines. This method can be calibrated to other types of scatterable antipersonnel mines in future trials to aid humanitarian demining initiatives. With millions of remnant PFM-1 and similar scatterable plastic mines across post-conflict regions and considerable stockpiles of these landmines posing long-term humanitarian and economic threats to impacted communities, our methodology could considerably aid in efforts to demine impacted regions.

Recent advances in autonomous unmanned aerial vehicle (UAV) technology, along with successful efforts to miniaturize total field magnetometers, offer a unique opportunity to test low-cost UAV-mounted systems for wide-area high-resolution magnetic surveys. Modern UAV platforms capable of flying at low altitudes and collecting dense aerial surveys, coupled with sensitive and compact instruments, allow identification of anthropogenic targets previously identifiable only in ground magnetometer surveys. We present results of a proof-of-concept study focused on developing and field testing a UAV-based magnetometer system to detect and identify abandoned and unmarked oil and gas wells in an area of historical hydrocarbon exploration and development in New York state. Our results indicate that magnetic anomalies associated with metal casing of vertical wells are pronounced considerably above background levels both at the surface and up to 50 m above-ground elevation. We determine that a detection altitude of 40 m is optimal to avoid any canopy interference while recording magnetic data at the highest signal-to-noise ratio. This methodology makes rapid detection and identification of unmarked wells possible and, in turn, allows for future sustainable development of these areas.

Use of landmines as a weapon of unconventional warfare rapidly increased in armed conflicts of the last century and some estimates suggest that at least 100 million remain in place across post-conflict nations. Among munitions and explosives of concern (MECs), aerially deployed plastic anti-personnel mines are particularly challenging in terms of their detection and subsequent disposal. Detection and identification of MECs largely relies on the geophysical principles of magnetometry and electromagnetic-induction (EMI), which makes non-magnetic plastic MECs particularly difficult to detect and extremely dangerous to clear. In a recent study we demonstrated the potential of time-lapse thermal-imaging technology to detect unique thermal signatures associated with plastic MECs. Here, we present the results of a series of field trials demonstrating the viability of low-cost unmanned aerial vehicles (UAVs) equipped with infrared cameras to detect and identify the most notorious plastic landmines—the Soviet-era PFM-1 aerially deployed antipersonnel mine. We present results of an experiment simulating analysis of a full-scale ballistic PFM-1 minefield and demonstrate our ability to accurately detect and identify all elements associated with this type of deployment. We report significantly reduced time and equipment costs associated with the use of a UAV-mounted infrared system and anticipate its utility to both the scientific and non-governmental organization (NGO) community.

Abrupt velocity gradients in the upper mantle, detectable by receiver functions (RF) techniques, have been known to exist down to the depths of ∼110 km beneath northeastern North America. Comparisons with the surface wave velocity models have designated some negative velocity gradients (NVGs) as the lithosphere‐asthenosphere boundary (LAB), delineating a relatively thin lithosphere beneath this region. This work presents a systematic survey of upper mantle layering in seismic properties using P‐S RF analysis at 62 long‐running sites with dense lateral sampling. We examine both radial and transverse component RF for indicators of seismic anisotropy and adopt the notion of seismic attributes, utilized in active‐source seismology, to characterize the spatial distribution of directionally variant and invariant signal components. We confirm a widespread presence of NVGs at depths 60–100 km throughout the region, consistent with previous studies using mode‐converted body waves. We also find numerous converting boundaries that reflect changes in directional variation (anisotropy) of seismic velocity, indicating complexity of rock texture in the upper mantle. Some of these boundaries appear as deep as 185 km, implying that the lithosphere extends much deeper than the widespread NVGs would suggest. In this, our results agree with recent estimates of the lithospheric thickness in thermodynamically consistent models combining seismic, gravity, and heat flow constraints.

Across postconflict regions of the world, explosive ordnance (EO), which includes remnant antipersonnel land mines, antivehicle/tank mines, unexploded cluster munitions, improvised explosive devices, and explosive remnants of war (ERW) such as unexploded ordnance and abandoned explosive ordnance, remains a critical humanitarian concern. Clearance and land release efforts anchored on manual geophysical detection and mechanical probing methods remain painstakingly slow, expensive, and dangerous to operators. As a result, postconflict regions impacted by EO contamination significantly lag in social and economic development. Developing, calibrating, and field testing more efficient detection methods for surficial EO is a crucial task. Unpiloted aerial systems featuring advanced remote sensing capabilities are a key technology that may allow the tide to turn in the EO crisis. Specifically, recent advances in hardware design have allowed for effective deployment of small, light, and less power consuming hyperspectral imaging (HSI) systems from small unpiloted aerial vehicles (UAVs). Our proof-of-concept study employs UAV-based HSI to deliver a safer, faster, and more cost-efficient method of surface land mine and ERW detection compared to current ground-based detection methods. Our results indicate that analysis of HSI data sets can produce spectral profiles and derivative data products to distinguish multiple ERW and mine types in a variety of host environments.

An apparent gap in the Andean volcanic arc in the Pampean section of the subduction zone in Chile (~28°–33°S) marks a section of flat slab subduction. In this tectonic environment, the fate of fluids released from the subducting Nazca slab remains uncertain and the degree of their interaction with the basal layer of the continental lithosphere is poorly understood. Results of a RF investigation and forward modeling effort at three long‐running stations of the Chilean National Seismic Network allow us to constrain the position of the subducting Nazca slab and to address the physical properties of the interplate contact zone in Central Chile. Our observations suggest a transition in seismic character, from a weakly anisotropic contact in the normally subducting section north of the flat slab region to a strongly anisotropic plate contact within the flat slab region. We attribute this change to a transition from sheared olivine to serpentinized peridotite generated as a result of fluid release across the flat slab. This interpretation is supported by forward modeling synthetic RFs at each of the stations. We propose that the identified layer extends across the flat slab region, acting as a mineral reservoir that captures and, possibly, transports fluids from the dehydrating Nazca Plate as it subducts below South America. We note that the Ps converted phase at the slab interface at southernmost station GO04 suffers a 2‐s discontinuity at 180° back azimuth, consistent with a 15–20‐km scarp or kink in the Nazca slab to the south of the station.