Groundbreaking geological map modernises understanding of the rocks beneath the Greenland Ice Sheet
FOR IMMEDIATE RELEASE: Wednesday 17 April 2024
-With images-
A team of international scientists has unveiled a ground-breaking new map of the geological provinces hidden beneath the Greenland Ice Sheet.
This comprehensive synthesis, published in Geophysical Research Letters, promises to advance our understanding of this critical component of the global climate system.
This new subglacial geology map provides an invaluable modernised framework for interpreting the solid earth properties that shape the Greenland Ice Sheet's past, present, and future behaviour.
Using a new wealth of geophysical data, including seismic, gravity, magnetic, and topographic surveys, the researchers have meticulously delineated the boundaries of geological provinces across the island and – critically – beneath the ice.
This updated map represents a significant advancement over previous efforts, which were hampered by limited data available at the time. By combining diverse geophysical datasets, the researchers have been able to map Greenland’s subsurface structure in unprecedented detail, revealing a far more complex picture than was previously known.
Lead author of the study, Dr Joseph MacGregor from NASA's Goddard Space Flight Centre said: "This new map will help unlock a wealth of insights about Greenland's geological evolution and its interactions with the ice sheet.
"It will serve as an invaluable tool for researchers seeking to understand how the rocks beneath the ice sheet affect how it flows, which is crucial for improving projections of future sea level rise."
Notably, the team's findings show that north of 72°N, Greenland's geology is clearly more heterogeneous than previously thought.
There are also three distinct subglacial regions identified in central and northern Greenland whose unique geophysical signatures do not align with the island's marginal geology.
Study co-author Dr Guy Paxman of Durham University said: "These unresolved regions are a tantalising puzzle. Their distinct characteristics suggest the presence of as-yet-unknown geological provinces.
“They show that there is still more to learn about this hidden environment, which could have significant implications for understanding Greenland's glacial history and future response to climate change."
Further, the researchers detected intriguing geophysical anomalies aligned with the onset regions of the Petermann Glacier and the Northeast Greenland Ice Stream – two of Greenland's most dynamic outlet glaciers.
This discovery points to a potential link between subglacial geology and ice sheet dynamics, a relationship that warrants deeper investigation.
In addition to these findings, the team's analysis of surface topography data revealed an extensive network of remarkably long, straight, and parallel subglacial valleys crossing Greenland's interior.
These features, which remain poorly resolved in current topographic models, may hold clues about the island's tectonic history and could provide new avenues for investigating the ice sheet's past dynamics.
This study is a collaborative effort involving scientists from NASA, the Geological Survey of Denmark and Greenland, Durham University, Columbia University, the University at Buffalo, the Université du Québec à Montréal, the University of Alaska Fairbanks, the University of Florida, Dartmouth College, and Princeton University.
ENDS
Media Information
Dr Guy Paxman from Durham University is available for interview and can be contacted on guy.j.paxman@durham.ac.uk.
Alternatively, please contact Durham University Communications Office for interview requests on communications.team@durham.ac.uk or +44 (0)191 334 8623.
Source
‘Geologic provinces beneath the Greenland Ice Sheet constrained by geophysical data synthesis’, (2024), J. A. MacGregor et. al., Geophysical Research Letters, 51, e2023GL107357. https://doi.org/10.1029/2023GL107357
Map - https://doi.org/10.22008/FK2/BUQQ9C
Graphics
Associated images are available via the following link: https://www.dropbox.com/scl/fo/elgqn47dhyoenaof2yygr/AM2EGhVUXI67FXHjR5aTdXY?rlkey=3z1rk1wd4dnz68w25frn3e26e&dl=0
Credit: Jeremy Harbeck / NASA
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END OF MEDIA RELEASE – issued by Durham University Communications Office.
JOURNAL
Geophysical Research Letters
Dense network of seismometers reveals how the underground ruptures
The first high-precision image of a seismic fault zone changes our understanding of earthquakes
IMAGE:
THE SKETCH SHOWS THE 100 TO 600 METERS THICK SEISMOGENIC ZONE IN WHICH THE FAULT PLANES (5 TO 20 METERS THICK) AND THUS THE RUPTURES LIE.
view moreCREDIT: DR. CAROLINE CHALUMEAU, DR. HANS ARGURTO-DETZEL, PROF. ANDREAS RIETBROCK, DR. MICHAEL FRIETSCH. PROF. ONNO ONCKEN, DR. MONICA SEGOVIA, DR. AUDREY GALVE: SEISMOLOGICAL EVIDENCE FOR A MULTIFAULT NETWORK AT THE SUBDUCTION INTERFACE. NATURE, 2024. DOI: 10.1038/S41586-024-07245-Y
The idea that earthquakes release stress by a single strong quake along a single fault plane may need to be corrected. A recent study by researchers from the Karlsruhe Institute of Technology (KIT) with the participation of the GFZ German Research Centre for Geosciences and international partner institutions points out that it would be more accurate to speak of a zone with numerous fault planes, some of which are parallel. According to the authors, the results of the study can help to create more realistic models for earthquakes and earthquake hazards in subduction zones. The study has been published in the current issue of the journal Nature.
The international team led by first author Caroline Chalumeau from KIT investigated a series of earthquakes in Ecuador on the west coast of South America. There, the Pacific Plate is subducted beneath the continental South American Plate. Subduction repeatedly leads to very severe earthquakes. The most recent series of earthquakes in Taiwan, the main quake of which killed nine people and caused extensive damage on Taiwan’s east coast at the beginning of April, can also be attributed to subduction.
The series of earthquakes in Ecuador analyzed by the team began on 12 March 2022 and ended on 26 May 2022. The most severe quake (magnitude 5.8) occurred on March 27 and triggered many smaller aftershocks over a short period of time. A dense network of 100 seismometers was located in the region at this time. It had been set up for the offshore experiment "High-resolution imaging of the subduction fault in the Pedernales Earthquake Rupture zone" (HIPER for short).
With the extraordinarily detailed data from the HIPER experiment and using artificial intelligence, the researchers were able to map more than 1,500 earthquakes and their respective fault planes at a depth of 15 to 20 kilometers in very high resolution. "We observed that the seismicity of earthquakes occurred in a primary region - the main earthquake, so to speak - and in a secondary region, i.e. the aftershocks," says first author Dr. Caroline Chalumeau from the Geophysical Institute (GPI) at KIT. "Within the primary region, we observed that the seismicity occurred on several different fault planes, often on top of each other. In some places, parallel seismically active planes occurred, in other places only single ones."
The parallelism of the quakes was not linked to a specific depth. "We have found indications that the previous idea that the stress is released by a single strong quake along a single fault plane could be a thing of the past," says Professor Andreas Rietbrock from the GPI. "Instead, we should rather speak of a fault network in which a series of ruptures discharges within a single earthquake."
The analysis of the Ecuadorian quake series also provides new insights into aftershocks. These first occurred near the epicenter of the main quake and then gradually spread in other directions, says Chalumeau. She concludes from this that the propagation of aftershocks in the region is mainly controlled by afterslip. Prof. Onno Oncken from the GFZ says: "With this work, Caroline Chalumeau's team has presented the first sharp seismological image of a seismogenic plate boundary. On the one hand, it confirms existing geological observations and, on the other hand, successfully explains the propagation of aftershocks with a new approach. Previous assumptions that, for example, fluid diffusion causes aftershocks have thus been refuted."
The results are also important for assessing the earthquake risk in subduction zones. "The study will influence the future modeling of earthquakes, but also of aseismic slips, i.e. plate movements without earthquakes," says Andreas Rietbrock.
Original publication
Dr. Caroline Chalumeau, Dr. Hans Argurto-Detzel, Prof. Andreas Rietbrock, Dr. Michael Frietsch. Prof. Onno Oncken, Dr. Monica Segovia, Dr. Audrey Galve: Seismological evidence for a multifault network at the subduction interface. Nature, 2024. DOI: 10.1038/s41586-024-07245-y
https://www.nature.com/articles/s41586-024-07245-y
Scientific contact:
Prof. Onno Oncken (please be aware that he is away on fieldwork and see here for contacts at KIT)
Media Contact:
Josef Zens
JOURNAL
Nature
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Seismological evidence for a multifault network at the subduction interface
ARTICLE PUBLICATION DATE
18-Apr-2024
COI STATEMENT
No conflicts of interest declared
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