B.1 | Solid Earth Sciences

B.1

Solid Earth Sciences

Orals

| Wed, 09 Oct, 15:15–15:30 (CEST)|Lecture Hall, Building H

Posters

| Attendance Wed, 09 Oct, 16:00–17:30 (CEST)|Foyer, Building H

This session invites presentations about studies of glacial isostatic adjustment, the Earth's crustal structure, lithospheric and mantle properties, analyses of seismic events, etc., using information from long-term mean and time-variable gravity field models.

Orals: Wed, 9 Oct | Lecture Hall, Building H

15:15–15:30

GSTM2024-81

On-site presentation

GRACE and GRACE-FO constraints on 3D GIA models

Wouter van der Wal, Javier Fullea, Olga Ortega, Ernst Schrama, and Bart Root

Glacial isostatic adjustment is the response of the solid Earth to past ice sheets. It is the largest secular gravity increase in GRACE and GRACE-FO data. Models of GIA are used to correct GRACE observations for ice mass and sea level change, but in areas where GIA is the main signal GRACE data can be used to constrain GIA models. Global GIA models increasingly use 3D variations in viscosity which can have large uncertainties resulting from the conversion of seismic velocity anomalies to viscosity. By ‘anchoring’ the GIA model to GRACE observed values in some regions confidence in its performance in other regions can be increased.

Here, we compare predicted gravity rate from a global GIA model with 3D viscosity to gravity rate in North America and Scandinavia derived from gravity rate trends estimates from GRACE and GRACE-FO data from 2003-2023. 3D viscosity maps are derived from upper mantle model WINTERC-G with a flow law for mantle material olivine, in which material parameters such as grain size and water content are varied. We use a GIA model based on the commercial FEM package ABAQUS and use the ICE-7G ice loading history as forcing.

The GIA simulations mostly result in gravity rates larger than observed for North America, while in Scandinavia they are mostly too small. Both regions prefer a dry mantle rheology, which is expected for the relatively colder mantle in the regions. The best fitting GIA models are used to correct GRACE and GRACE-FO data and estimate global sea level change due to land ice melt of about 1.6 mm/year, which is at the lower end of the predictions for different GIA models including traditional models with only radially varying viscosity.

How to cite: van der Wal, W., Fullea, J., Ortega, O., Schrama, E., and Root, B.: GRACE and GRACE-FO constraints on 3D GIA models, GRACE/GRACE-FO Science Team Meeting, Potsdam, Germany, 8–10 Oct 2024, GSTM2024-81, https://doi.org/10.5194/gstm2024-81, 2024.

Posters: Wed, 9 Oct, 16:00–17:30 | Foyer, Building H

P10

GSTM2024-16

The Solid Earth Response to Earthquake Cycle Processes and Glacial Fluctuations in the Eastern Aleutians of Alaska

Jeanne Sauber, Shin-Chan Han, Michael Croteau, Stacey Huang, and Bryant Loomis

We are processing and analyzing broad-scale gravimetric change from GRACE-GFO and ongoing crustal deformation with Sentinel-1 InSAR data integrated with continuous GPS data to unravel and model the temporal and spatial sources of gravimetric change and surface deformation in the Kodiak-Katmai region of the eastern Aleutians of Alaska. As background, the Kodiak-Katmai segment of the eastern Alaska-Aleutian subduction zone experienced large coseismic slip during the great 1964 earthquake (M=9.2). Furthermore, the largest volcanic eruption of the twentieth century (VEI = 6) occurred in 1912 at the Novarupta volcano, 10 km to the west of Mount Katmai on the Alaska Peninsula. Here, we report the simulated coseismic and postseismic gravimetric change associated with the 2021 Chignik earthquake (M=8.2) that occurred southwest of our study area. Earlier, we estimated the predicted ongoing rate of gravimetric change due to the post-seismic response to the 1964 great earthquake; however, more recent sources of gravimetric change make it difficult to detect this signal. Some of the individual volcanoes monitored now with InSAR in the Katmai complex have undergone volcanic surface deformation in the last decade. We hypothesize that some of the observed vertical land motion across the Kodiak-Katmai region includes a discernible component of surface uplift due to ongoing regional deglaciation of the Katmai area glaciers based on our initial examination of continuous GPS data from this area, as well as earlier seismic cycle, glacier retreat, and volcanic models of the predicted surface deformation. We anticipate our study results will enable better characterization of geohazards associated with the subduction main thrust zone, upper crustal faults, ongoing volcanic processes, and post-glacial rebound. We will discuss the implications of our current work on constraining earthquake source parameters and Earth rheology that can be derived from gravimetric and surface deformation change data in the context of our broader study of earthquakes with GRACE-GFO data over the last two decades.

How to cite: Sauber, J., Han, S.-C., Croteau, M., Huang, S., and Loomis, B.: The Solid Earth Response to Earthquake Cycle Processes and Glacial Fluctuations in the Eastern Aleutians of Alaska, GRACE/GRACE-FO Science Team Meeting, Potsdam, Germany, 8–10 Oct 2024, GSTM2024-16, https://doi.org/10.5194/gstm2024-16, 2024.