Muography for structural characterization of volcanoes: a case study at Mount Unzen, Japan

Estimation of the magmatic contribution to soil air at Unzen Volcano, SW Japan, was carried out using carbon isotopes, both 14C and 13C, and a mixing model of isotopic mass balance in order to assess the spatial variation of magmatic influence from the volcano. The advantage of using soil air samples is that a wide range of gas sampling sites can be selected. Magmatic CO2 contributed mostly in the eastern region from Unzen Volcano. The high magmatic contribution to soil air appeared along the Akamatsudani fault zone located southeast of the volcano. Our observations across the fault also showed remarkable peaks of CO2 concentration and δ13C values, suggesting that magmatic fluid comes up along the fracture zone as for the normal fault system of the graben.

Vertical mapping of hydrothermal fluids and alteration from bulk conductivity: Simple interpretation on the USDP-1 site, Unzen Volcano, SW Japan

Tapping into an unconventional reservoir such as naturally fractured tight carbonate or basement has become more common in the industry. Open natural fractures, when present are the major contributor to production flow in such formation. Therefore, a comprehensive understanding of fracture properties including aperture, intensity, and permeability is required to identify the productive fractures and optimize production. In this paper, we discuss the first application of the latest Logging-While Drilling (LWD) high-resolution laterolog resistivity image in combination with LWD multi-pole sonic to provide comprehensive fracture characterization in Pre-Talang Akar Formation tight carbonate reservoir, in the offshore North West Java Basin, Indonesia. The methodology involved identification of borehole breakouts, natural or drilling-induced fractures, faults and vugs from the high-resolution LWD image data, which were then interpreted further to provide the fracture attributes and the secondary porosity distributions from each of the identified features. The Stoneley measurement from LWD multi-pole sonic log enabled the analysis of the fracture system producibility using the sonic fracture technique. The characterization of fractures and faults (open/closed) from the integration of these two independent methods were complemented by the triple combo measurements, caliper, and drilling loss data, as well as sonic compressional and shear data. This methodology has successfully managed to differentiate open fracture zones and closed fracture zones along with their computed fracture properties. The open fracture zones were characterized by a cluster of conductive fractures with large fracture aperture and fracture porosity value. These fractures were also associated with positive fracture indication from the sonic data, decrease in density logs, shallow - deep resistivity log separation and drilling loss occurrence. Whereas, closed fracture zones were characterized with minor fracture dip development. It also showed negative open fracture indication from sonic data, flat density log response and overlaying resistivity log response with no drilling loss occurrence. The case study in this paper shows excellent LWD data quality and fracture characterization result, on par with wireline conveyed data that were commonly used to quantify fracture attributes. The results provide invaluable information for volumetric calculation, well completion and production planning in this area.

Three AGU members were among 37 people killed June 3 when Mount Unzen, a volcano in Nagasaki prefecture, Japan, erupted. Unzen last erupted in 1792. The first signs of renewed activity appeared in mid‐1990, with increases in seismicity and the first volcanic tremor since observations began in 1966. The three volcanologists, Harry Glicken and Maurice and Katia Krafft, had traveled to Mount Unzen to monitor the increased seismic activity. Glicken, 33, was a visiting scientist at Tokyo Metropolitan University and an assistant researcher in geological sciences at the University of California, Santa Barbara. He worked for the U.S. Geological Survey until 1989, and narrowly escaped death in the 1980 eruption of Mount St. Helens in Washington.Glicken had been an AGU member since 1980 and was known for his work in debris avalanches. Maurice, 45, and Katia Krafft, 44, of Cernay, France, were professional volcanologists known for their extensive work in publishing books and films on volcanology for the general public. Both Kraffts joined AGU in 1975.

In situ observation of dome instabilities at Merapi volcano, Indonesia: A new tool for volcanic hazard mitigation

Internal structure and deformation of an unstable crystalline rock mass above Randa (Switzerland): Part I — Internal structure from integrated geological and geophysical investigations

Menchaca comments: The account by Bogdan C. Maglich on unpublished details of the Chephren pyramid experiment by Luis Alvarez and coworkers 1 1. L. W. Alvarez et al., Science 167, 832 (1970). https://doi.org/10.1126/science.167.3919.832 provides fascinating insight into this pioneering application of high-energy physics to archaeology. The method used by Alvarez involves finding statistically significant differences between measured and simulated muon flows in a given direction. The necessary ignorance of a detailed density distribution inside the investigated volume requires an approximation. As Maglich implies, both we and the Alvarez group assumed that the internal pyramid density is constant. Also, we are aware 2 2. R. Alfaro et al., Rev. Mex. Fis. 49(S4), 54 (2003). of the limitations introduced, not only by uncertainties related to the internal density distribution, but also by uncertainties about the external shape description, among other factors.In Teotihuacan we assume that the mean composition and density distribution are similar to those found inside a 200-meter-long horizontal tunnel excavated near the base of the Pyramid of the Sun last century. We sampled the pyramid filling along that tunnel. The study reveals that the Mexican monument, although fairly uniform, is more heterogeneous than the Egyptian pyramid seems to be as judged by the limestone walls of the tunnel leading to the Belzoni chamber, where the Alvarez team located its muon detector. The measured mean density in Teotihuacan turns out to be appreciably smaller than the density of rock. As Maglich correctly suggests, we do consider the conditions in which stony walls of a hypothetical hidden cavity would result in a compensated mean density that would cancel the sought-for signal. This and other considerations helped determine the limitations of our experiment. 2 2. R. Alfaro et al., Rev. Mex. Fis. 49(S4), 54 (2003). In contrast with the Chephren case, archaeological excavations in the Pyramid of the Sun provide excellent calibration references. Finally, in the Egyptian case, we tend to agree with the private response Maglich says he received from Alvarez concerning the unlikely possibility that a cavity having a granite ceiling would result in mean density compensation in all directions. That would be particularly unlikely with internal structures as large and intricate as those found in the Cheops pyramid.REFERENCESSection:ChooseTop of pageREFERENCES <<1. L. W. Alvarez et al., Science 167, 832 (1970). https://doi.org/10.1126/science.167.3919.832 , Google ScholarCrossref, CAS2. R. Alfaro et al., Rev. Mex. Fis. 49(S4), 54 (2003). Google Scholar© 2004 American Institute of Physics.

Increasing water cut in oil-producing zones is a common issue faced by operators, particularly for mature fields. Currently, where most of the decisions are governed by economics, incurring additional expenses with activities such as handling produced water becomes extremely undesirable. Depending upon the nature of the zone, one effective solution to this issue is chemical isolation. This paper undertakes this issue, discussing a case study of a successful zonal isolation operation using an organically crosslinked polymer sealant in a fractured zone with a gravel pack and screen completion for a reservoir with a subhydrostatic nature. This zone was an initial oil producer in FM-01 sand of the Mangala onshore oil field and had been stimulated in 2011 with a fracture-pack completion. The zone was completed with screens and a gravel pack with 16/30-mesh sand and 5.5-in. screens across the producing interval. During a period of time, the zone (FM-01) began to produce a significant amount of water, resulting in excessive water cut. To mitigate the issue, it was decided to completely isolate the zone using an organically crosslinked polymer system as a porosity fill sealant. When prepared in the appropriate concentration, subject to reservoir temperature, this low-viscosity formulation (40 to 80 cp) turns into a permanent rigid gel with time. The particular challenges of this operation were the presence of high permeability streaks because of stimulation by hydraulic fracturing, extra pore space because the perforated interval lay within the gravel-packed screens, and the subhydrostatic nature of the reservoir. Extensive laboratory testing was performed to optimize the formulation at the desired temperature, measuring the time necessary for the viscosity to begin increasing and the minimum total time necessary to form a rigid gel. The case study discussed in this paper features the successful application of the treatment using the spot-and-squeeze method with coiled tubing (CT) for the isolation of the zone. After allowing the setting time, pressure tests were performed, indicating positive isolation of the zone. After the pressure test, a jet pump was installed, and a drawdown was created to flow the zone. It was observed that production post operation was almost 95% less than production before operation at the same pressure drawdown, indicating approximately 100% zone isolation.

Despite the fact that 90% of global seismicity occurs at plate boundary faults, our understanding of their internal structure is lacking. It’s not easy to see inside a plate boundary fault – typically composed of a high-strain fault core surrounded by a fractured damage zone – and when we can, it often requires expensive drilling projects that yield limited information on the internal structure of the whole fault. Understanding the internal structure of large faults is crucial, because their chemical and mechanical properties control how and where earthquakes rupture, nucleate and propagate. This in turn limits the size of the earthquake or the amount of radiated seismic energy, and consequently the severity of surface damage. The 1999 magnitude 7.7 earthquake along the Chelungpu plate boundary fault, for example – the second deadliest earthquake in Taiwan’s recorded history – saw significant variations in slip and ground motion at different locations along the fault which resulted in large local variations in casualties and damage. Subsequent field investigations related these variations to changes in the fault’s structure (i.e., clay width, geometry), which in turn controlled how the fault moved.

The Unzen Volcano was active from 1990 to 1994 and in total 13 dacite lava lobes were formed successively at the eastern shoulder of Mount Fugen-dake. Surface temperature observation with nighttime Landsat-5 Thematic Mapper (TM) was conducted at the Unzen Volcano. The thermal anomaly areas up to 0.7 km2 were detected in all the 23 cloud-free images of Landsat TM band 7. The patterns of temperature distribution correspond to the lava dome and the pyroclastic flow activity. The hot area change has been found to be closely related to the lava effusion rate.

Casing deformation is an engineering problem that restricts the efficient development of shale gas in the Sichuan Basin. This paper analyzed the correlation between 67 casing deformation points and 256 fracture zones in the N201 wellfield, and conducted a statistical analysis of the distribution of the orientation of fracture zones, which may have/have not caused casing deformation. The Mohr–Coulomb criterion was used to analyze the stress state and the slip risk of these fracture zones. The results show indicate the following. (1) Fracture zone is the main factor leading to casing deformation. (2) Fracture zones with 60°–90° and 110°–120° orientations are likely to cause casing deformation, whereas fracture zones with 50°–70° orientation are relatively less likely to cause casing deformation. (3) The analysis of stress state shows that the orientations of high-risk fractures range from 74°–100° and 130°–160°, the orientations of medium-risk fractures range from 64°–74°, 100°–130°, and 160°–170 °, and the orientations of low-risk fractures are in the range of 0°–64° and 170°–180°. The theoretical results are basically consistent with the field statistical results. These results provide an explanation for the field statistical results in theory. This work not only demonstrates that a fracture zone is the major geological factor that causes casing deformation, but also provides a feasible method for us to predict the casing deformation in the future.

Major slope failures are a significant degradational process at volcanoes. Slope failures and associated explosive eruptions have resulted in more than 20 000 fatalities in the past 400 years; the historic record provides evidence for at least six of these events in the past century. Several historic debris avalanches exceed 1 km3 in volume. Holocene avalanches an order of magnitude larger have traveled 50–100 km from the source volcano and affected areas of 500–1500 km2. Historic eruptions associated with major slope failures include those with a magmatic component (Bezymianny type) and those solely phreatic (Bandai type). The associated gravitational failures remove major segments of the volcanoes, creating massive horseshoe-shaped depressions commonly of caldera size. The paroxysmal phase of a Bezymianny-type eruption may include powerful lateral explosions and pumiceous pyroclastic flows; it is often followed by construction of lava dome or pyroclastic cone in the new crater. Bandai-type eruptions begin and end with the paroxysmal phase, during which slope failure removes a portion of the edifice. Massive volcanic landslides can also occur without related explosive eruptions, as at the Unzen volcano in 1792. The main potential hazards from these events derive from lateral blasts, the debris avalanche itself, and avalanche-induced tsunamis. Lateral blasts produced by sudden decompression of hydrothermal and/or magmatic systems can devastate areas in excess of 500km2 at velocities exceeding 100 m s−1. The ratio of area covered to distance traveled for the Mount St. Helens and Bezymianny lateral blasts exceeds that of many pyroclastic flows or surges of comparable volume. The potential for large-scale lateral blasts is likely related to the location of magma at the time of slope failure and appears highest when magma has intruded into the upper edifice, as at Mount St. Helens and Bezymianny. Debris avalanches can move faster than 100 ms−1 and travel tens of kilometers. When not confined by valley walls, avalanches can affect wide areas beyond the volcano's flanks. Tsunamis from debris avalanches at coastal volcanoes have caused more fatalities than have the landslides themselves or associated eruptions. The probable travel distance (L) of avalanches can be estimated by considering the potential vertical drop (H). Data from a catalog of around 200 debris avalanches indicates that the H/L rations for avalanches with volumes of 0.1–1 km3 average 0.13 and range 0.09–0.18; for avalanches exceeding 1 km3, H/L ratios average 0.09 and range 0.5–0.13. Large-scale deformation of the volcanic edefice and intense local seismicity precede many slope failures and can indicate the likely failure direction and orientation of potential lateral blasts. The nature and duration of precursory activity vary widely, and the timing of slope faliure greatly affects the type of associated eruption. Bandai-type eruptions are particularly difficult to anticipate because they typically climax suddenly without precursory eruptions and may be preceded by only short periods of seismicity.

Multi-geophysical approaches to detect karst channels underground — A case study in Mengzi of Yunnan Province, China

Three-dimensional critical slip surface locating and slope stability assessment for lava lobe of Unzen volcano

Long-term monitoring and adaptive ecological management are essential to the conservation of biodiversity. Yet, achieving successful long-term ecological monitoring and management, especially at the landscape level, has proven challenging. In this paper, we address the hurdles faced in sustaining long-term monitoring and management for landscape-scale efforts by offering three promising conceptual and methodological developments that support such initiatives. Then, we introduce L-TEAM, a long-term ecological adaptive monitoring and management framework that integrates those three components using four tools: a conceptual model, clearly defined and measurable objectives, scientifically robust experimentation, and decision support tools. Finally, using a case study, we demonstrate L-TEAM’s effectiveness in supporting the long-term monitoring and management of a landscape conservation project with diverse habitat types and multiple management objectives. This structured decision framework not only facilitates informed decision making in management practices, but also ensures the implementation of scientifically grounded long-term monitoring. Additionally, L-TEAM holds the potential to enhance our understanding of ecosystem functioning and biodiversity responses to disturbances and management actions.