On April 29, 2015, the U.S. Geological Survey (USGS) reported five earthquakes in Oklahoma of magnitude 2.5 or greater—that is, tremors strong enough to be felt. The most powerful of these was a M4.1 earthquake 21 km (13 mi) west of the city of Perry in north-central Oklahoma. Based on recent evidence reported by the USGS, these earthquakes were almost certainly induced by human activity as a consequence of the injection of wastewater from oil and gas production into deep disposal wells. See also: Earthquake; Oil and gas field exploitation; Well

On April 25, 2015 at 11:56 a.m local time, a magnitude 7.8 earthquake struck in the district of Lamjung, approximately 80 km northwest of Kathmandu, Nepal. The earthquake, now known as the Gorkha quake, occurred as the result of thrust faulting [15.0 km (9.3 mi) in depth] in the region where the India plate is sinking (subducting) beneath the Eurasia plate, according to the United States Geological Survey (USGS). Damage to buildings was extensive and over 8700 people were killed. See also: Earthquake; Fault and fault structures; Subduction zones

A magnitude 5.1 nuclear test was detected 376 km (234 mi) NE of Pyongyang, North Korea (DPRK) on January 6, 2015 at 10:30 a.m. local time (01:30 UTC), according to the U.S. Geological Survey (USGS). The event was picked up at seismic stations around the world. The Comprehensive Nuclear-Test-Ban Treaty Organisation (CTBTO) said that the explosion occurred in roughly the same area as North Korea’s previous nuclear test on February 12, 2013. See also: Nuclear explosion; Nuclear testing; Seismographic instrumentation

A powerful magnitude 7.8 earthquake struck Ecuador on April 16, 2016 at 6:58 p.m. local time, causing extensive damage to buildings and infrastructure as well as hundreds of fatalities and thousands of injuries. The epicenter was located 52.0 km (32.3 mi) west of Rosa Zarate. The earthquake occurred as the result of thrust faulting 19.2 km (11.9 mi) in depth near the boundary of the Nazca and Pacific plates, according to the U.S. Geological Survey (USGS). See also: Earthquake; Fault and fault structures; Subduction zones

On August 5, 2018 at 6:46 p.m. local time, a magnitude 6.9 earthquake struck in Pulau Lombok, Indonesia. The earthquake occurred as the result of thrust faulting at a depth of 10.5 km (6.5 mi) in northern Lombok, according to the United States Geological Survey (USGS). A tsunami warning was issued, but was lifted after only small waves were recorded. Early reports stated that 98 people were killed and more than 200 injured, as the earthquake caused many buildings to collapse. Some structures that collapsed had already been damaged one week earlier (June 29, 2018) when a magnitude 6.4 earthquake struck Lombok, killing 17 people and injuring more than 160. Indonesia is located in a very seismically active zone, in which magnitude 5.0 or greater earthquakes were recorded on 17 of 31 days in July 2018. See also: Earthquake; Earthquake engineering; Fault and fault structures; Seismology; Tsunami

Obscured by a hazy atmosphere 100 times thicker than Earth's, Venus is a notoriously difficult world to study. Ground temperatures on Venus exceed 450°C (842°F)—enough to melt lead and to have quickly degraded the Soviet robotic landers last placed there 40 years ago. Yet orbiting spacecraft have successfully mapped this planet with cloud-piercing radar, as well as identified constituent surface materials via narrow bands of infrared light that escape the Venusian atmosphere. Those investigations have revealed unmistakable volcanic structures and solidified lava flows, although there remains no definitive evidence as to whether volcanic eruptions still occur. Now, a new study suggests that such evidence is already in hand and points to Venus as the only other volcanically active planet in the solar system. See also: Atmosphere; Radar; Venus; Volcano

Until recent years, the research focus on the high-energy photons known as gamma rays has been on nuclear and cosmic sources for them. Now it has moved to the cloud—the thundercloud, that is—where short bursts of gamma rays, known as terrestrial gamma ray flashes (TGFs) or dark lightning, have been observed. In a thunderstorm, a gamma-ray burst occurs when electrons accelerated by a strong electric field to almost the speed of light collide with air molecules. See also: Electric field; Gamma-ray burst; Gamma rays; Photon; Thunderstorm

Each year in the United States, landslides and debris flows kill an estimated 25 to 50 people and cause roughly $1 billion in property damage. A deeper understanding of the specific mechanisms through which landslides occur could help guide architects and engineers in reducing this loss of life and property. In an October 2022 study published in the Proceedings of the National Academy of Sciences, a joint team of geophysicists and mechanical engineers from the University of Pennsylvania and University of California, Santa Barbara applied recent advances in the physics of dense suspensions (heterogeneous mixtures of solids and liquids) in an attempt to better model complex debris flows. The team determined that an existing model for simple, ideal flows can be extended to account for complex, natural flows. The results accordingly offer a way to improve hazard assessment of hillslopes and their constituent materials. See also: Geophysical fluid dynamics; Geophysics; Landslide; Mass wasting; Suspension

Europa, one of the four largest natural satellites, or moons, orbiting the planet Jupiter, may be the first planetary body in the solar system other than Earth to show evidence of plate tectonics, a research team from the University of Idaho and Johns Hopkins University reported in Nature Geoscience (September 2014). The evidence comes from images sent back from the Galileo spacecraft, which passed Europa 17 times during its orbit of Jupiter between 1995 and 2003. See also: Galileo mission (Jupiter); Galileo observations of Jovian satellites; Jupiter; Satellite (astronomy); Solar system; Space probe

Glacial earthquakes are moderate (roughly magnitude 5) seismic events that occur when ice flowing to the ocean from large glaciers, or ice sheets, breaks off (calves). They were discovered in 2003 by Göran Ekström and coworkers as an anomalous signal that was teased out of the records of the Global Seismographic Network (GSN), which consists of more than 150 stations for real-time monitoring of all earth oscillations, great and small. See also: Earthquake; Glacial geology and landforms; Glaciology; Iceberg; Seismographic instrumentation; Seismology