Events

Each year, the week before AGU’s Fall Meeting, we invite UTIG students researchers to practice their AGU talks. Each presenter will be given 11 minutes, as per AGU’s oral presentation for 2024, followed by a few minutes for Q&A and feedback.

Talk ONE

Speaker: McKenzie Carlson

Title: Dynamic triggering of near-trench slow slip at the Hikurangi subduction zone documented in IODP borehole observatories

Abstract: Recurring offshore slow slip events (SSEs) at the Hikurangi Subduction Zone have been well documented by GNSS stations along the east coast of Aotearoa-New Zealand. Recent years have seen vast improvements in observations of these events with the addition of seafloor geodesy (seafloor pressure and GNSS-acoustic sensors), but the ability of these sensors to detect events is limited by oceanographic noise. Borehole pore pressure sensors provide a higher resolution view of offshore transient deformation, with enhanced signal-to-noise ratio compared to other seafloor geodetic techniques.

Here, we present near-field observations of slow slip from a transect of two IODP borehole observatories measuring changes in formation pore pressure (as a proxy for volumetric strain) installed near the trench in 2018 at the offshore Hikurangi subduction margin. Site U1518 is located ~5 km landward of the trench and crosses the Pāpaku Fault, an active splay fault. Site U1519 is located ~40 km landward of the trench, overlying the region of peak slip in previously reported SSEs. The observatory data reveal numerous pore pressure changes between 2018 and 2023, representing strain transients associated with slow slip events. Of particular interest is a large, near-trench transient deformation event observed at both observatories following the March 2021 sequence of earthquakes at the Kermadec Trench. We invert the observations (jointly with onshore GNSS displacements and seafloor pressure observations) for slip distributions during the triggered event, using material properties derived from laboratory experiments on core material to quantitatively map the observed pressure changes to volumetric strain. Large strain at Site U1518 contrasts with a much smaller strain transient, at Site U1519 and onshore GNSS stations during this event. This suggests that the dynamically triggered SSE took place in the near trench region (<4-5 km depth), and/or involved slip on the Pāpaku Fault. Our observations of near trench dynamic triggering have important implications for dynamic triggering processes on the shallow megathrust, and the rheology, slip behavior, and strength of the shallow plate boundary.

Talk TWO

Speaker: Medha Prakash

Title: Remote Sensing Investigations of Suevite in Schrödinger Basin

Abstract: Suevite is one of the various rock types produced during impact crater formation. It incorporates fragments of rocks that have experienced extreme heat and pressure to none at all. Through analysis of data collected via satellites and the many missions sent to the Moon, we have identified a bulk deposit of suevite in Schrödinger basin. Schrödinger basin is a 320-km wide impact basin located on the far-side of the lunar south pole, and is the deployment site of geophysical instruments as a part of the Artemis program. Specific lines of evidence supporting this include the textural resemblances to suevite on Earth, the higher erosional resistance compared to surrounding material, its glassy spectral signature, and the magnitude of its thickness compared to that of suevite deposits in terrestrial impact craters. Additionally, it’s found atop high elevation areas and throughout the impact basin, indicating that a fast-moving flow was necessary for it to be deposited. This deposit would be relevant to understanding the physics of the formation of Schrödinger basin. It would also be important for the future construction and resource utilization on the Moon, as the terrestrial counterpart has been used similarly, thus is a material of scientific and commercial interest.

Talk THREE

Speaker: Mercedes Jordan

Title: Utilizing Heterogeneities in Lunar Radar Sounder Surface Reflectivity to Identify Metallic Oxides in the Procellarum KREEP Terrane

Abstract: The Kaguya spacecraft orbited the Moon between 2007 and 2008, collecting thousands of tracks of radar data using its onboard Lunar Radar Sounder (LRS) instrument, transmitting a chirped signal centered at 5 MHz with a wavelength of 75 m. We have extracted LRS surface echoes and calibrated them using the laboratory-measured permittivity of Chang’e-5 samples, returned to Earth in late 2020. Such a calibration was made possible by radar’s dependency on permittivity, a complex quantity where the real part describes a material’s ability to be polarized by an electromagnetic wave and the imaginary part describes energy loss via conductivity. The power of these surface reflections is reliant on surface texture/topography and near-surface properties (i.e., permittivity, porosity, density, etc.) tens of meters into the subsurface and can therefore be used as a proxy to identify accessible resources, not only at the surface where these materials can be recognized via spectroscopy, but to a depth of 50-75 m. To test the utility of surface reflectance power for identifying subsurface materials, we mapped surface reflectivity in the Procellarum KREEP Terrane (PKT), the largest continuous extent of mare basalt on the Moon. Quantitative correlations between common metallic oxides, TiO₂ and FeO, and surface echo power in this region show that reflectance increases with increasing metallic oxide abundance. Empirical relationships exist relating ilmenite content (FeTiO₃) with the imaginary part of permittivity, but effects on the real part have been argued to be negligible. Further investigation will determine whether variations in the imaginary part of permittivity alone can generate the differences in reflectance power observed in lunar maria.

Talk FOUR

Speaker: Julia Miller

Title: Preconditions of wildfires vary within Europe

Abstract: In the past three summers (2021-2023), wildfires broke records in terms of extent and severity in many regions of Europe. Not only were fire-prone areas such as the Mediterranean affected, but also regions where large fires are not very common, such as Germany and Switzerland. The occurrence of such severe wildfires is favored by a combination of hydroclimatic and land surface conditions of hot, dry and windy weather leading to low soil moisture and drying of biomass, supporting the spread of fires. These drivers operate on a range of temporal scales and vary across climate regions, making it difficult to understand which interactions of anomalous conditions lead to low-frequency but high-impact fire events.
Here, we analyze the preconditions of different hydroclimatic and land surface drivers prior to fire events to assess temporal scales at which they influence fire occurrence and how they interact among each other. Our analysis leverages ESA’s Fire Climate Change Initiative burned area pixel product (ESA FireCCI) together with MODIS gross primary productivity (GPP) data and the Copernicus European Regional ReAnalysis (CERRA) dataset from 2001 to 2020. We distinguish between eight climate regions and differentiate between mountain and non-mountain regions to learn if wildfires show different or similar patterns depending on elevation.

We find that fire preconditions differ between climate regions. For example, in Southern Europe, high temperature and high vapor pressure deficit are the most important preconditions, whereas in Scandinavia, low soil moisture and low snow depth also contribute to the occurrence of large wildfires. We observe that wildfires in mountain regions have a pronounced winter seasonality across all subregions and develop under cold and dry weather conditions. Further, our results illustrate the important role of drivers acting on longer temporal scales. By analyzing all variables iteratively over time steps of up to 24 months prior to fire events, we show how soil moisture and GPP modulate fire event size up to a year before the respective events.

Our findings on the spatial and temporal variety of wildfire drivers across diverse climate regions in Europe provide valuable insights into interannual wildfire risk and can pave the way for improving long-term fire prediction and preparedness.