Article
Multidisciplinary Sciences
V Rubino, N. Lapusta, A. J. Rosakis
Summary: Lab experiments show that dynamic ruptures propagate through fault regions with fine rock gouge through complex and intermittent slip processes. These processes include repeated arrest of rupture propagation caused by friction strengthening at lower slip rates, and dynamic earthquake re-nucleation enabled by pronounced rapid friction weakening at higher slip rates.
Article
Multidisciplinary Sciences
Yixin Liu, Chuanhua Xu, Jiang Xu, Xuemin Zeng
Summary: The injection of fluids into fault gouges can disturb stress conditions and increase the risk of earthquakes. This study investigates the effect of water injection and shear deformation on the hydro-mechanical characteristics of fault gouges. The results show that injecting water significantly reduces the maximum shear strength, and the effect varies with the gouge fill material. Shear deformation increases the inhomogeneity of thickness distribution and leads to non-uniform distribution of injected water along the fault.
SCIENTIFIC REPORTS
(2022)
Article
Geology
Harold J. Tobin, Demian M. Saffer, David A. Castillo, Takehiro Hirose
Summary: This study successfully constrained the in situ pore pressure and stress state in the deep interior of an accretionary wedge using data from drilling in the Nankai subduction zone. The estimated stress components helped reveal the tectonic stress characteristics in the region, indicating a normal or strike-slip faulting regime with low stress variations.
Article
Geochemistry & Geophysics
Matt J. Ikari, Andre Huepers
Summary: In laboratory simulations of lithification process, it was found that samples with at least 30% halite content exhibit a combination of velocity strengthening and significant velocity weakening in frictional behavior. The occurrence of velocity weakening is associated with cohesion and porosity reduction in lithified samples, supporting the lithification hypothesis for seismic slip.
EARTH AND PLANETARY SCIENCE LETTERS
(2021)
Article
Geochemistry & Geophysics
Xiaofeng Chen, Sai Sandeep Chitta, Ximeng Zu, Ze'ev Reches
Summary: This study investigates the weakening processes of faults during earthquakes, emphasizing that the weakening at the rupture-front is more efficient than frictional weakening. Experimental results show that the rupture-front can rapidly weaken the entire fault, possibly occurring in natural faults as well.
EARTH AND PLANETARY SCIENCE LETTERS
(2021)
Article
Geochemistry & Geophysics
S. Nielsen, E. Spagnuolo, M. Violay, G. Di Toro
Summary: This study explores rock friction under crustal earthquake conditions and finds that faults undergo abrupt dynamic weakening. Different models are tested to explain the process, and it is found that a model considering both heat sources and sinks better fits the experimental results. The study also compares three numerical approximations for computing temperature in this type of problem.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2021)
Article
Geochemistry & Geophysics
James S. Neely, Seth Stein
Summary: Continental normal fault earthquakes have smaller maximum magnitudes compared to earthquakes with other fault geometries, primarily due to the lithosphere yield stress. This contrasts significantly with earthquakes in compressional settings, but is inconsistent with the occurrence of large oceanic normal fault earthquakes. The main limiting factor for earthquake maximum magnitude appears to be yield stress, rather than fault geometry alone.
Article
Geochemistry & Geophysics
Xiang Chen, Hongfeng Yang, Mingpei Jin
Summary: Understanding fault friction and rupture dynamics is crucial for assessing earthquake hazards. Critical slip-weakening distance (Dc) is a key parameter, but is difficult to determine on natural faults. For strike-slip earthquakes, Dc can be estimated directly from double near-fault ground displacement, providing valuable insights into earthquake source characteristics.
SEISMOLOGICAL RESEARCH LETTERS
(2021)
Article
Geochemistry & Geophysics
Y. Benjelloun, J. de Sigoyer, S. Garambois, J. Carcaillet, Y. Klinger
Summary: The study investigates the Holocene paleoseismic activity of the North Anatolian Fault (NAF) in the Marmara region, using high-resolution satellite imagery and terrestrial cosmogenic nuclide dating to map the middle strand. The research found evidence of multiple major ruptures and determined the horizontal slip rate in the area, suggesting that the last large earthquakes occurred between 1065 CE and the 14th-18th centuries CE, indicating a potential for future destructive seismic activity.
Article
Geochemistry & Geophysics
Jaime E. Delano, Rich W. Briggs, Christopher B. DuRoss, Ryan D. Gold
Summary: The study compares the use of physical scale bars with total station or GNSS control points to constrain SfM models for paleoseismic trench mapping. Despite slightly decreased accuracy, scale bars significantly simplify the workflow and eliminate the need for specialized survey equipment.
SEISMOLOGICAL RESEARCH LETTERS
(2021)
Article
Environmental Sciences
Evangelos Moulas, Boris Kaus, Bjorn Jamtveit
Summary: The metamorphism of dry, lower crust in orogens is often localized in shear zones composed of mechanically weaker rocks. Previous studies have suggested that shear zone development is preceded by brittle faults, which provide the necessary pathways for fluid migration and metamorphism. However, there is currently no unified model that links long-term geological deformation to fluid migration and metamorphic reactions. This study presents a visco-elasto-plastic model that explains the observed features of transformed lower crust through basic mechanical principles. This includes dynamic and heterogeneous pressure distribution in the reacting and deforming rock volumes, which can significantly impact fluid migration patterns and explain discrepancies in tectonic settings and inferred burial depths.
COMMUNICATIONS EARTH & ENVIRONMENT
(2022)
Article
Geosciences, Multidisciplinary
Cheng Mei, Sylvain Barbot, Wei Wu
Summary: The Parkfield tremors exhibit period-multiplying slow and fast ruptures, providing new insights into earthquake cycles. Direct-shear experiments on polycarbonate and granite fractures reveal variations in rupture properties near the stability transition, leading to slip-predictable cycles with correlative acoustic energy release and stress drop. Changes in stiffness and stress drops ratios over multiple cycles affect recurrence intervals and energy release of consecutive slip events, confirming the link between low-frequency earthquakes and slow-slip events.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Engineering, Civil
K. S. K. Karthik Reddy, Sahithi Veggalam, Surendra Nadh Somala
Summary: The collapse fragility of structures is investigated through the use of subshear and supershear earthquakes. The study finds that supershear earthquakes exhibit significant differences in ground motion characteristics compared to subshear ruptures, with a dominant fault parallel component. Fragility curves are derived based on stations parallel and perpendicular to the fault at various distances in the near-field. The study also examines the differences between subshear and supershear cases by applying fault-parallel and fault-normal components to single-degree-of-freedom systems. Comparisons with HAZUS suggested values are provided.
Article
Geosciences, Multidisciplinary
Jamie D. Howarth, Nicolas C. Barth, Sean J. Fitzsimons, Keith Richards-Dinger, Kate J. Clark, Glenn P. Biasi, Ursula A. Cochran, Robert M. Langridge, Kelvin R. Berryman, Rupert Sutherland
Summary: The study reveals that the rupture mode between major and great earthquakes is controlled by transform fault geometry, impacting the behavior of earthquakes. By analyzing the spatial and temporal patterns of earthquake terminations, the study uncovers along-strike patterns of rupture extent and two modes of earthquake behavior characterized by major and great earthquakes. Physics-based simulations of seismic cycles closely resemble the observations, suggesting that the switching between rupture modes is due to heterogeneous stress states evolving over multiple seismic cycles in response to geometric complexities.
Article
Geochemistry & Geophysics
Qing-Yu Wang, Michel Campillo, Florent Brenguier, Albanne Lecointre, Tetsuya Takeda, Keisuke Yoshida
Summary: Using ambient-noise-based seismic monitoring, we detected an anomalous seismic velocity decrease in Honshu about one year after the 2011 Tohoku-Oki earthquake, suggesting a possible relation to volcanic processes and internal physical changes. Tiltmeter observations revealed temporal variations correlated with velocity changes, supporting the hypothesis of actual physical deformation in the crust. The observed decrease in fault strength and concurrent increase in low-frequency events in the volcanic area further indicate changes in physical properties and an increase in pore pressure in the upper crust.
EARTH AND PLANETARY SCIENCE LETTERS
(2021)
Article
Geochemistry & Geophysics
Jack N. Williams, Luke N. J. Wedmore, Christopher A. Scholz, Folarin Kolawole, Lachlan J. M. Wright, Donna J. Shillington, Ake Fagereng, Juliet Biggs, Hassan Mdala, Zuze Dulanya, Felix Mphepo, Patrick R. N. Chindandali, Maximilian J. Werner
Summary: The Malawi Active Fault Database (MAFD) is an open-access geospatial database containing 113 fault traces in Malawi and neighboring Tanzania and Mozambique. It is used to understand the regional seismic hazard and tectonic evolution. The MAFD incorporates a multidisciplinary dataset including digital elevation models, geological mapping, seismic reflection surveys, and magnetic and gravity data. The study finds that the distribution of fault lengths in Malawi follows a power law.
GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS
(2022)
Article
Geosciences, Multidisciplinary
Jack N. Williams, Ake Fagereng, Luke N. J. Wedmore, Juliet Biggs, Hassan Mdala, Felix Mphepo, Michael Hodge
Summary: This study investigates the earthquake energy dissipation along low displacement faults and the impact of pre-existing weaknesses. The research findings suggest that low displacement faults consume more energy through fracturing and fault formation compared to mature faults. However, minimal evidence was found for earthquake energy dissipation in the surrounding wall rock of the Bilila-Mtakataka Fault in Malawi, despite geomorphic evidence for M-W 7.5-8 earthquakes.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Review
Geochemistry & Geophysics
Randolph T. Williams, Ake Fagereng
Summary: Quartz cementation may play an important role in strength recovery between earthquakes, but its growth rate is limited. It cannot explain the formation of mesoscale fault-fracture networks, but can occur rapidly on principal slip surfaces. Understanding the control of quartz cementation rates is crucial for a complete understanding of strength recovery following earthquake rupture.
REVIEWS OF GEOPHYSICS
(2022)
Article
Geochemistry & Geophysics
R. M. Churchill, M. J. Werner, J. Biggs, A. Fagereng
Summary: Aseismic afterslip can significantly redistribute crustal stresses and drive aftershock sequences. This study analyzed 148 afterslip studies following large earthquakes and found that afterslip and coseismic moments scale near-linearly. The study also identified the scaling relationships between afterslip area and average slip with coseismic moment. The ratio of afterslip to coseismic moment varied widely and was influenced by various factors.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2022)
Article
Geochemistry & Geophysics
C. J. Tulley, A. Fagereng, K. Ujiie, J. F. A. Diener, C. Harris
Summary: Geophysical observations suggest that localized fracturing may occur within otherwise viscous regions of subduction plate boundaries, impacting the estimation of the seismic zone extent. The composition of the subducting oceanic lithosphere plays a significant role in controlling dehydration reactions and slip style variations.
GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS
(2022)
Article
Geochemistry & Geophysics
Kohtaro Ujiie, Kazuya Noro, Norio Shigematsu, Ake Fagereng, Naoki Nishiyama, Christopher J. Tulley, Haruna Masuyama, Yasushi Mori, Hiroyuki Kagi
Summary: Metasomatic reactions can influence the slip behavior of the seismogenic zone and potentially explain the depth-dependent changes in slip mode observed in subduction melanges.
GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS
(2022)
Article
Geochemistry & Geophysics
H. Leah, A. Fagereng, N. Groome, D. Buchs, A. Eijsink, A. Niemeijer
Summary: This paper investigates the Neoproterozoic oceanic sequences in Anglesey, UK and reveals the presence of melange materials derived from adjacent ocean plate stratigraphy (OPS). The study suggests that chlorite veins in subducting volcanics may localize deformation in the seismogenic zone. This research is important for understanding sedimentary inputs in active subduction zones, the role of fluids in the deforming zone, and the mechanism of earthquakes.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2022)
Article
Geosciences, Multidisciplinary
H. Leah, A. Fagereng
Summary: This work investigates the relationship between mineral-scale deformation mechanisms and structural evolution during subduction, and provides examples of how grain-scale heterogeneities facilitate viscous creep in calcite at seismogenic temperatures. The study finds that fine grain size heterogeneities in calcite can localize shear strain and activate relatively rapid creep, reducing elastic strain accumulation during interseismic periods and decreasing the likelihood of large earthquakes.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Geosciences, Multidisciplinary
Adam Beall, Martijn van den Ende, Jean-Paul Ampuero, Fabio A. Capitanio, Ake Fagereng
Summary: Estimating the likelihood of earthquake magnitudes is crucial for assessing seismic hazards. This study uses numerical models to reproduce the relationship between stress and earthquake magnitudes and finds that stress influences the likelihood of fault rupture and the length of the rupture. The study also proposes a probabilistic clustering model to explain the observed relationship between earthquake magnitudes and recurrence.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Geosciences, Multidisciplinary
C. J. Tulley, A. Fagereng, K. Ujiie, S. Piazolo, M. S. Tarling, Y. Mori
Summary: This study reveals the deformation mechanisms and rheological behavior of antigorite, suggesting that dissolution-precipitation creep and dislocation activity contribute to the foliation development of antigorite.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Geosciences, Multidisciplinary
Manon Carpenter, Jack N. Williams, Ake Fagereng, Luke N. J. Wedmore, Juliet Biggs, Felix Mphepo, Hassan Mdala, Zuze Dulanya, Blackwell Manda
Summary: The early stages of normal fault growth in the Zomba Graben have been investigated through field observations. The study provides insights into the displacement of active border and intrarift faults, as well as the extent of fault damage and mineralisation associated with their surface exposures. The results suggest that the Zomba border fault has a wider fault zone compared to the intrarift faults, with greater fault damage and mineral alteration. The research findings also highlight the rapid lengthening of normal faults in the area, despite their low displacement.
JOURNAL OF STRUCTURAL GEOLOGY
(2022)
Article
Geochemistry & Geophysics
J. N. Williams, M. J. Werner, K. Goda, L. N. J. Wedmore, R. De Risi, J. Biggs, H. Mdala, Z. Dulanya, A. Fagereng, F. Mphepo, P. Chindandali
Summary: Historical and instrumental earthquake catalogs may not accurately reflect the long-term distribution of seismicity in low strain rate regions. Therefore, probabilistic seismic hazard analysis (PSHA) should consider geologic and geodetic data to incorporate fault-based seismogenic sources. The study explores these issues in the context of a new PSHA for Malawi, which has a thick seismogenic layer and a growing exposure to seismic hazard. The results emphasize the importance of careful fault source modeling in PSHA and the need for new fault-based PSHA in the East Africa Rift.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geosciences, Multidisciplinary
Jack N. Williams, Luke N. J. Wedmore, Ake Fagereng, Maximilian J. Werner, Hassan Mdala, Donna J. Shillington, Christopher A. Scholz, Folarin Kolawole, Lachlan J. M. Wright, Juliet Biggs, Zuze Dulanya, Felix Mphepo, Patrick Chindandali
Summary: This study presents a model describing the seismogenic properties of faults in Malawi, providing insights into earthquake hazards in the region. The results suggest that large-magnitude earthquakes may occur in Malawi, although their frequency is low.
NATURAL HAZARDS AND EARTH SYSTEM SCIENCES
(2022)
Article
Geochemistry & Geophysics
Erik M. Young, Christie D. Rowe, James D. Kirkpatrick
Summary: Crustal shear zones generate earthquakes, but their prediction is currently unpredictable. Studying the architecture of fault zones can reveal the controls on fault rupture, locking, and reloading, which influence the spatial and temporal patterns of earthquakes. The Pofadder Shear Zone in South Africa provides insights into ancient earthquake structures. A high-resolution geological map of the shear zone core mylonite zone was made, revealing layers of black ultramylonite and their relation to ancient earthquake rupture surfaces. The geometry of lithologic interfaces affected earthquake rupture paths.
Review
Environmental Sciences
James D. Kirkpatrick, Ake Fagereng, David R. Shelly
Summary: The recognition of slow earthquakes has transformed the understanding of plate motion mechanisms, but the mechanics behind slow earthquakes remain enigmatic. Geoscientists have synthesized geological observations of ancient deformation structures to gain insights into fault slip mechanics.
NATURE REVIEWS EARTH & ENVIRONMENT
(2021)