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Recent investigations in polar environments have examined solid-Earth-ice-sheet feedbacks and have emphasized that glacial isostatic adjustment, tectonic, and geothermal forcings exert first-order control on the physical conditions at and below the ice-bed interface and must be taken into account when evaluating ice-sheet evolution. However, the solid-Earth structure beneath much of Antarctica is still poorly constrained given the sparse distribution of seismic stations across the continent and the generally low seismicity rate. One region of particular interest is the Wilkes Subglacial Basin (WSB) in East Antarctica. During the mid-Pliocene warm period, the WSB may have contributed 3-4 m to the estimated 20 m rise in sea-level, indicating that this region could also play an important role in future warming scenarios. However, the WSB may have experienced notable bedrock uplift since the Pliocene; therefore, past geologic inferences of instability may not serve as a simple analogue for the future. Using records of ambient seismic noise recorded by both temporary and long-term seismic networks, along with a full-waveform tomographic inversion technique, we are developing improved images of the lithospheric structure beneath East Antarctica, including the WSB. Empirical Green’s Functions with periods between 40 and 340 s have been extracted using a frequency-time normalization technique, and a finite-difference approach with a spherical grid has been employed to numerically model synthetic seismograms. Associated sensitivity kernels have also been constructed using a scattering integral method. Our preliminary results suggest the WSB is underlain by slow seismic velocities, with faster seismic structure beneath the adjacent Transantarctic Mountains and the Belgica Subglacial Highlands. This may indicate that the WSB is associated with a region of thinner lithosphere, possibly associated with prior continental rifting. The seismic heterogeneity highlighted in our model could have significant implications for understanding the geodynamic origin of WSB topography and its influence on ice-sheet behavior. 

As seismic data availability increases, the necessity for automated processing techniques has become increasingly evident. Expanded geophysical datasets collected over the past several decades across Antarctica provide excellent resources to evaluate different event detection approaches. We have used the traditional Short-Term Average/Long-Term Average (STA/LTA) algorithm to catalogue seismic data recorded by 19 stations in East Antarctica between 2012 and 2015. However, the complexities of the East Antarctic dataset, including low magnitude earthquakes and other types of seismic events such as icequakes or firnquakes, warrant more advanced automated detection techniques. Therefore, we have also applied template matching as well as several deep learning algorithms, including Generalized Phase Detection (GPD), PhaseNet, BasicPhaseAE, and EQTransformer (EQT), to identify seismic phases within our dataset. Our goal is not only to increase the volume of detectable seismic events but also to gain insights into the effectiveness of these different automated approaches. Our assessment evaluates the completeness of the newly generated catalogs, the precision of identified event locations, and the quality of the picks. The performance of these different event detection techniques applied to continuous seismic data from a polar environment will be highlighted. We will also identify potential limitations and necessary adjustments for deep learning algorithm training, which is essential for their reliable application to specific datasets. 

Recent investigations in polar environments have examined solid-Earth-ice-sheet feedbacks and have emphasized that glacial isostatic adjustment, tectonic, and geothermal forcings exert first-order control on the physical conditions at and below the ice-bed interface and must be taken into account when evaluating ice-sheet evolution. However, the solid-Earth structure beneath much of Antarctica is still poorly constrained given the sparse distribution of seismic stations across the continent and the generally low seismicity rate. One region of particular interest is the Wilkes Subglacial Basin (WSB) in East Antarctica. During the mid-Pliocene warm period, the WSB may have contributed 3-4 m to the estimated 20 m rise in sea-level, indicating that this region could also play an important role in future warming scenarios. However, the WSB may have experienced notable bedrock uplift since the Pliocene; therefore, past geologic inferences of instability may not serve as a simple analogue for the future. Using records of ambient seismic noise recorded by both temporary and long-term seismic networks, along with a full-waveform tomographic inversion technique, we are developing improved images of the lithospheric structure beneath East Antarctica, including the WSB. Empirical Green’s Functions with periods between 40 and 340 s have been extracted using a frequency-time normalization technique, and a finite-difference approach with a spherical grid has been employed to numerically model synthetic seismograms. Associated sensitivity kernels have also been constructed using a scattering integral method. Our preliminary results suggest the WSB is underlain by slow seismic velocities, with faster seismic structure beneath the adjacent Transantarctic Mountains and the Belgica Subglacial Highlands. This may indicate that the WSB is associated with a region of thinner lithosphere, possibly associated with prior continental rifting. The seismic heterogeneity highlighted in our model could have significant implications for understanding the geodynamic origin of WSB topography and its influence on ice-sheet behavior. 

Inward-sloping marine basins in polar environments are susceptible to an effect known as the marine ice-sheet instability (MISI): run-away ice stream drainage caused by warm ocean water eroding the ice shelf from below. The magnitude and timing of the MISI response strongly depend on the physical conditions along the ice-bed interface, which are controlled by the tectonic evolution of the basin. Solid Earth parameters, such as topography, geothermal heat flux, and mantle viscosity, play critical roles in ice-sheet stability. However, in most cases, these solid-Earth parameters for regions susceptible to the MISI are largely unknown. The Wilkes Subglacial Basin (WSB) is a critical region in East Antarctica that may be susceptible to the MISI, which may have led to significant sea-level contributions in the past and which could play an important role in the future. During the mid-Pliocene warm period, the WSB may have contributed 3-4 m to the estimated 20 m increase in sea-level compared to present day. However, recent work has suggested that the WSB may have undergone significant bedrock uplift since the Pliocene; therefore, geological inferences of instability during the Pliocene may not serve as a simple analogue for future warming scenarios. Further constraints are required to assess the geodynamic origin of WSB topography and the influence of geologic parameters on past, current, and future ice-sheet behavior. To this end, we have proposed an integrated investigation of the WSB, combining geophysical analyses with both mantle flow and ice-sheet modeling. Using seismic and magnetotelluric observations from a new field deployment (WIDGET), in conjunction with existing geophysical and geological data, we will develop an improved tectonic model for the region and will estimate the thermal, density, and viscosity structure of the crust and upper mantle beneath the WSB. These solid Earth constraints will be used to simulate mantle flow and to assess paleotopography, which will allow us to model both past and future ice-sheet stability, thereby creating scientifically and societally relevant estimates of sea-level change. 

Anomalies along Earth’s core can be explained by former oceanic seafloor that descended 3000 km to the base of the mantle. 

The origin of the Cameroon Volcanic Line (CVL), which is difficult to explain with traditional plate tectonics and mantle convection models because the volcanism does not display clear age progression, remains widely debated. Existing seismic tomography models show anomalously slow structure beneath the CVL, which some have interpreted to reflect upper mantle convective processes, possibly associated with edge‐driven flow related to the neighboring Congo Craton. However, mid‐ and lower mantle depths are generally not well resolved in these models, making it difficult to determine the extent of the anomalous CVL structure. Here, we present a new P‐wave velocity model for the African mantle, developed with the largest collection of travel‐time residuals recorded across the continent to date and an adaptive model parameterization. Our extensive data set and inversion method yield high resolution images of the mantle structure beneath western Africa, particularly at the critical mid‐ and lower mantle depths needed to further evaluate processes associated with the formation of the CVL. Our new model provides strong evidence for a connection between the African Large Low Velocity Province, centered in the lower mantle beneath southern Africa, and the continental portion of the CVL. We suggest that seismically slow material generated near the core‐mantle boundary beneath southern Africa moves northwestward under the Congo Craton. At the northern edge of the craton, the hot, buoyant material rises through the upper mantle, causing the CVL volcanism. Consequently, CVL magmatism can be linked to large‐scale mantle processes rooted in the deep mantle.

 

The origins of tectonic structures in East Antarctica, such as the Gamburtsev Subglacial Mountains (GSMs), the Wilkes Subglacial Basin (WSB), the Aurora Subglacial Basin (ASB), and the Transantarctic Mountains (TAMs), are not clearly understood. Previous investigations have proposed multiple origin models to explain the formation of these structures; however, existing tomographic images lack resolution and consistency given the sparse seismic coverage in East Antarctica. We use full-waveform ambient noise tomography to model the shear-wave velocity structure beneath East Antarctica to further investigate these features. We extract Rayleigh-wave Empirical Green’s Func-tions (EGFs) between periods of 15 and 340 secs from ambient seismic noise using a frequency time normalization technique. Synthetic waveforms are simulated through a 3-D heterogenous Earth model with a lateral grid spacing of 0.025º (~2.25 km) using a finite-difference wave propagation method. The synthetic seismograms are cross-correlated with the EGFs to measure the phase delays. The fi-nite-frequency sensitivity kernels are calculated using the scattering-integral approach and the shear-wave velocity model is computed by inverting the phase delays using a sparse damped least-square inversion method. Preliminary results show fast seismic velocities beneath the WSB, which may be associated with thick and stable lithosphere, and slow velocities beneath the ASB, possibly reflecting old rift systems or other inherited tectonic structures. Slow upper mantle velocities are also observed beneath the TAMs, possibly associated with a thermal load that contributes to the uplift of the moun-tain range. Slow shear-wave velocities in the vicinity of the GSMs may be associated with rifting along the extended Lambert Rift System. Our final tomographic model and associated tectonic inter-pretations will be shared. 

The thick ice coverage and harsh climatic conditions in East Antarctica hinder detailed investigations of tectonic features, leading to debates regarding the origin and evolution of the Gamburtsev Subglacial Mountains (GSM), the Wilkes Subglacial Basin (WSB), the Aurora Subglacial Basin (ASB), and the Transantarctic Mountains (TAMs). Present tomographic models lack resolution and consistency given the minimal seismic coverage in East Antarctica. To further such investigations, we are using full-waveform ambient noise tomography to model shear-wave velocities and to constrain the crustal and upper mantle structure beneath East Antarctica. This approach utilizes Empirical Green’s functions (EGFs), which provides information about the Earth structure between recording stations and is an alternative approach compared to many traditional tomographic models. EGFs from ambient seismic noise between periods of 15-340 secs are extracted using a frequency-time normalization approach, and synthetic waveforms are simulated through a three-dimensional heterogeneous Earth model using a finite-difference wave propagation method with a grid spacing of 0.025º (~ 2.25 km). Phase delays are computed by cross correlating EGFs and the synthetics, and sensitivity kernels are constructed using a scattering integral approach. Preliminary results show slow velocities beneath both the WSB and ASB, possibly reflecting old rift systems or other inherited tectonic structures. A transition from slow to fast velocities beneath the Northern Victoria Land portion of the TAMs is consistent with thermal loading beneath the mountain range. Slow velocities beneath the GSM may be due to rifting associated with the extended Lambert Rift System. These preliminary results are currently being updated using a larger EGF dataset; our final model will be used to assess East Antarctic tectonic structures and to resolve the ambiguity associated with their origin models. 

Much of our knowledge on deep Earth structure is based on detailed analyses of seismic waveforms that often have small amplitude arrivals on seismograms; therefore, stacking is essential to obtain reliable signals above the noise level. We present a new iterative stacking scheme that incorporates Historical Interstation Pattern Referencing (HIPR) to improve data quality assessment. HIPR involves comparing travel‐time and data quality measurements between every station for every recorded event to establish historical patterns, which are then compared to individual measurements. Weights are determined based on the individual interstation measurement differences and their similarity to historical averages, and these weights are then used in our stacking algorithm. This approach not only refines the stacks made from high‐quality data but also allows some lower‐quality events that may have been dismissed with more traditional stacking approaches to contribute to our study. Our HIPR‐based stacking routine is illustrated through an application to core‐reflected PcP phases recorded by the Transantarctic Mountains Northern Network to investigate ultra‐low velocity zones (ULVZs). We focus on ULVZ structure to the east of New Zealand because this region is well‐sampled by our data set and also coincides with the boundary of the Pacific Large Low Shear Velocity Province (LLSVP), thereby allowing us to further assess possible ULVZ‐LLSVP relationships. The HIPR‐refined stacks display strong ULVZ evidence, and associated synthetic modeling suggests that the ULVZs in this region are likely associated with compositionally distinct material that has perhaps been swept by mantle convection currents to accumulate along the LLSVP boundary.

 

The origin and tectonic evolution of various features in East Antarctica, such as the Wilkes Subglacial Basin (WSB), Aurora Subglacial Basin (ASB), Transantarctic Mountains (TAMs), and Gamburtsev Subglacial Mountains (GSM), are unconstrained due to thick ice coverage and a lack of direct geologic samples. We are modeling the crustal and upper mantle structure beneath these areas using a full-waveform tomography method to further our understanding the tectonic evolution of the continent as well as the behavior of the overlying ice sheet. A frequency-time normalization approach is employed to extract empirical Green’s functions (EGFs) from ambient seismic noise, between periods of 15-340 seconds. EGF ray path coverage is dense throughout East Antarctica, indicating that our study will provide new, high resolution imaging of this area. Synthetic waveforms are simulated through a three-dimensional heterogeneous Earth model using a finite-difference wave propagation method with a grid spacing of 0.025º, which accurately reproduces Rayleigh waves at 15+ seconds. Following this, phase delays are measured between the synthetics and the data, sensitivity kernels are constructed using the scattering integral approach, and we invert using a sparse, least-squares method. Preliminary results show that slow velocities are present beneath both the WSB and ASB, possibly indicating old rift systems or other inherited tectonic structures. The transition from slow to fast velocities beneath the Northern Victoria Land section of the TAMs is consistent with thermal loading beneath the mountain range. The presence of slow velocities near the GSM may be associated with rifting along the Lambert Rift System.