Assessing the effect of hydraulic fracturing on microearthquakes
New research examines mining sites with hydraulic fracturing comparing it to those without to determine the practice’s effect on seismic hazards
Peer-Reviewed PublicationThe analysis of low-intensity human-caused microearthquakes, including their magnitude and frequency, has become an important factor in mining. This is a consideration not only for the safety of mining staff, but also for extraction rates and mine stability that can have major impacts on business performance.
Increasingly, the practice of hydraulic fracturing is used to precondition mines and diminish the magnitude of induced tremors as well as reduce the number of rock fragments extracted.
A new paper published in EPJ B assesses the impact of hydraulic fracturing on seismic hazards like microearthquakes, an important issue for the safety of workers and the continuation of mining operations. The paper is authored by Erick de la Barra, Pedro Vega-Jorquera and Héctor Torres from the University of La Serena, Chile, alongside Sérgio Luiz E. F. da Silva from Politecnico di Torino, Department of Applied Science and Technology, Turin, Italy.
Hydraulic fracturing involves pumping large quantities of fluids into a wellbore at high pressures. This has the effect of enlarging fractures in the target rock formation. This results in an increase in the yield of oil or gas from rocks — especially from low-permeability rocks like tight sandstone, shale and occasionally coal beds.
The authors attempt to quantify the benefits of preconditioning with hydraulic fracturing by integrating previous investigative models to create a more realistic approximation of the seismic ruptures.
This model was applied to a mine in the O’Higgins Region of Chile to assess induced seismic activity due to the effect of hydraulic fracturing. The team also considered both the magnitude of microearthquakes and the intervening time between events.
This was done by considering 15,436 microearthquakes recorded between 2003 and 2008 in three sections of the mine. These were then compared on the basis of whether the section had been preconditioned with hydraulic fracturing or not.
The results seemed to imply that hydraulic fracturing decreases the magnitude and the microearthquakes.
The model worked on by the team could also be utilised to predict seismic activity, and to understand so-called marsquakes occurring on the Red Planet.
“In reference to the next step in this investigation, our interest is to work with the problem when self-similarity is broken,” Vega-Jorquera says. “Thus, considering the problem of multisources and relating them to multimodal distributions, this would imply evaluating possible modifications of the seismic hazard via hydraulic fracturing.”
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References
de la Barra, E., Vega-Jorquera, P., da Silva, S.L.E.F. et al. Hydraulic fracturing assessment on seismic hazard by Tsallis statistics. Eur. Phys. J. B 95:92 (2022). https://doi.org/10.1140/epjb/s10051-022-00361-6
JOURNAL
The European Physical Journal B
ARTICLE TITLE
Hydraulic fracturing assessment on seismic hazard by Tsallis statistics
Geological carbon sequestration in mantle rocks prevents large earthquakes in parts of the San Andreas Fault
Smaller, more frequent quakes help to reduce tectonic
strain
Peer-Reviewed PublicationIMAGE: OUTCROP OF CARBONATE-ALTERED MANTLE ROCK IN THE SAN ANDREAS FAULT AREA. A RECENT STUDY SHOWS THAT CARBON SEQUESTRATION IN MANTLE ROCKS MAY PREVENT LARGE EARTHQUAKES IN PARTS OF THE SAN ANDREAS FAULT. view more
CREDIT: IMAGE CREDIT: FRIEDER KLEIN/©WOODS HOLE OCEANOGRAPHIC INSTITUTION
Woods Hole, MA - The San Andreas Fault in California is renowned for its large and infrequent earthquakes. However, some segments of the San Andreas Fault (SAF) instead are characterized by frequent quakes of small to moderate magnitude and high rates of continuous or episodic aseismic creep. With tectonic strain released in a quasi-steady motion, that reduces the potential for large earthquakes along those segments.
Now, researchers say ubiquitous evidence for ongoing geological carbon sequestration in mantle rocks in the creeping sections of the SAF is one underlying cause of aseismic creep along a roughly 150 kilometer-long SAF segment between San Juan Bautista and Parkfield, California, and along several other fault segments.
“Although there is no consensus regarding the underlying cause of aseismic creep, aqueous fluids and mechanically weak minerals appear to play a central role,” researchers say in a new paper, “Carbonation of serpentinite in creeping faults of California,” published in Geophysical Research Letters.
The new study integrates field observations and thermodynamic modeling “to examine possible relationships between the occurrence of serpentinite, silica-carbonate rock, and CO2-rich aqueous fluids in creeping faults of California,” the paper states. “Our models predict that carbonation of serpentinite leads to the formation of talc and magnesite, followed by silica-carbonate rock. While abundant exposures of silica-carbonate rock indicate complete carbonation, serpentinite hosted CO2-rich spring fluids are strongly supersaturated with talc at elevated temperatures. Hence, carbonation of serpentinite is likely ongoing in parts of the San Andres Fault system and operates in conjunction with other modes of talc formation that may further enhance the potential for aseismic creep, thereby limiting the potential for large earthquakes.”
The paper indicates that because wet talc is a mechanically weak mineral, “its formation through carbonation promotes tectonic movements without large earthquakes.”
The researchers recognized several possible underlying mechanisms causing aseismic creep in the SAF, and they also noted that because the rates of aseismic creep are significantly higher in some parts of the SAF system, an additional or different mechanism – the carbonation of serpentinite – is needed to account for the full extent of the creep.
With fluids basically everywhere along the SAF, but with only certain portions of the fault being lubricated, researchers considered that a rock could be responsible for the lubrication. Some earlier studies had suggested that the lubricant could be talc, a soft and slippery component that is commonly used in baby powder. A well-established mechanism for forming talc is by adding silica to mantle rocks. However, the researchers here focused on another talc-forming mechanism: adding CO2 to mantle rocks to form soapstone.
“The addition of CO2 to mantle rocks – which is the mineral carbonation or carbon sequestration process – had not previously been investigated in the context of earthquake formation or the natural prevention of earthquakes. Using basic geological constraints, our study showed where these carbonate-altered mantle rocks are and where there are springs along the fault line in California that are enriched in CO2. It turned out that when you plot the occurrence and distribution of these rock types and the occurrence of CO2-rich springs in California, they all line up along the San Andreas Fault in creeping sections of the fault where you don’t have major earthquakes,” said Frieder Klein, lead author of the journal article.
Klein, an associate scientist in the Marine Chemistry and Geochemistry Department at the Woods Hole Oceanographic Institution, explained that carbonation is basically the uptake of CO2 by a rock. Klein noted that he had used existing U.S. Geological Survey databases and Google Earth to plot the locations of carbonate-altered rocks and CO2-rich springs.
“The geological evidence suggests that this mineral carbonation process is taking place and that talc is an intermediary reaction product of that process,” Klein said. Although researchers did not find soapstone on mantle rock outcrops, results from theoretical models “strongly suggest that carbonation is an ongoing process and that soapstone indeed could form in the SAF at depth,” the paper notes.
These theoretical models “suggest that carbon sequestration with the SAF is taking place today and that the process is actively helping to lubricate the fault and minimize strong earthquakes in the creeping portions of the SAF,” Klein said.
The paper also notes that this mechanism may also be present in other fault systems. “Because CO2-rich aqueous fluids and ultramafic rocks are particularly common in young orogenic belts and subduction zones, the formation of talc via mineral carbonation may play a critical role in controlling the seismic behavior of major tectonic faults around the world.”
“Our study allows us to better understand the fundamental processes that are taking place within fault zones where these ingredients are present, and allows us to better understand the seismic behavior of these faults, some of which are in densely populated areas and some of which are in lightly populated or oceanic settings,” Klein said.
This work was supported by grants from the National Science Foundation.
Authors: Frieder Klein1*, David L. Goldsby2, Jian Lin1, Muriel Andreani3
Affiliations:
1Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA
2University of Pennsylvania, Department of Earth and Environmental Sciences, Philadelphia, PA, USA
3Laboratoire de Géologie de Lyon, UMR 5276, ENS et Université Lyon 1, 69622 Villeurbanne Cedex, France
*corresponding author
About Woods Hole Oceanographic Institution
The Woods Hole Oceanographic Institution (WHOI) is a private, non-profit organization on Cape Cod, Massachusetts, dedicated to marine research, engineering, and higher education. Established in 1930, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate an understanding of the ocean’s role in the changing global environment. WHOI’s pioneering discoveries stem from an ideal combination of science and engineering—one that has made it one of the most trusted and technically advanced leaders in basic and applied ocean research and exploration anywhere. WHOI is known for its multidisciplinary approach, superior ship operations, and unparalleled deep-sea robotics capabilities. We play a leading role in ocean observation and operate the most extensive suite of data-gathering platforms in the world. Top scientists, engineers, and students collaborate on more than 800 concurrent projects worldwide—both above and below the waves—pushing the boundaries of knowledge and possibility. For more information, please visit www.whoi.edu
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