A Significant Increase in Interplate Seismicity near Major Historical Earthquakes Offshore Martinique (FWI)

2021 ◽  
Author(s):  
Jordane Corbeau ◽  
O’Leary Gonzalez ◽  
Nathalie Feuillet ◽  
Anne-Marie Lejeune ◽  
Fabrice R. Fontaine ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Plate Boundary ◽  
Historical Earthquakes ◽  
Seismogenic Zone ◽  
Plate Interface ◽  
Seismicity Rate ◽  
Rupture Area ◽  
Interplate Seismicity ◽  
Statistical Studies

ABSTRACT Understanding the processes that may be at the origin of major earthquakes in subduction zones is highly challenging, especially in the case of slowly converging areas such as the Lesser Antilles subduction zone. Our study reveals a recorded increase in seismicity rate and cumulative seismic moment over the last two decades offshore Martinique island and, particularly, in the presumed rupture area of the major historical 1839 earthquake. This sustained seismicity is shared between extensive intermediate depth activity since the 2007 Mw 7.4 earthquake that occurred about 20 km north of Martinique and a compressive seismic cluster located in the seismogenic zone of the subduction zone. We also observe a downward migration of the seismicity along the plate interface up to a 60–65 km depth and a recorded increase in the magnitudes of the earthquakes. All these observations may indicate ongoing changes along the plate boundary interface near the area of the historical major rupture of 1839, although more detailed statistical studies and additional data are necessary to confirm this trend.

Warm thermal structures in subduction zones lead to ample dehydration at the depths of deep slow slip and tremor and resultant transformations in viscous rheology 

2021 ◽  
Author(s):  
Cailey Condit ◽  
Victor Guevara ◽  
Melodie French ◽  
Adam Holt ◽  
Jonathan Delph
Keyword(s):  
Subduction Zones ◽  
Thermal Structure ◽  
Fluid Pressure ◽  
Plate Boundary ◽  
Pore Fluid ◽  
Seismogenic Zone ◽  
Plate Interface ◽  
Dehydration Reactions ◽  
Episodic Tremor And Slip ◽  
Increased Strength

<p>Feedbacks amongst petrologic and mechanical processes along the subduction plate boundary play a central role influencing slip behaviors and deformation styles. Metamorphic reactions, resultant fluid production, deformation mechanisms, and strength are strongly temperature dependent, making the thermal structure of these zones a key control on slip behaviors.</p><p> </p><p>Firstly, we investigate the role of metamorphic devolatilization reactions in the production of Episodic Tremor and Slip (ETS) in warm subduction zones. Geophysical and geologic observations of ETS hosting subduction zones suggest the plate interface is fluid-rich and critically stressed, which together, suggests that this area is a zone of near lithostatic pore fluid pressure.  Fluids and high pore fluid pressures have been invoked in many models for ETS. However, whether these fluids are sourced from local dehydration reactions in particular lithologies, or via up-dip transport from greater depths remains an open question. We present thermodynamic models of the petrologic evolution of four lithologies typical of the plate interface along predicted pressure–temperature (P-T) paths for the plate boundary along Cascadia, Nankai, and Mexico which all exhibit ETS at depths between 25-65 km. Our models suggest that 1-2 wt% H<sub>2</sub>O is released at the depths of ETS along these subduction segments due to punctuated dehydration reactions within MORB, primarily through chlorite and/or lawsonite breakdown. These reactions produce sufficient in-situ fluid across this narrow P-T range to cause high pore fluid pressures. Punctuated dehydration of oceanic crust provides the dominant source of fluids at the base of the seismogenic zone in these warm subduction margins, and up-dip migration of fluids from deeper in the subduction zone is not required to produce ETS-facilitating high pore fluid pressures. These dehydration reactions not only produce metamorphic fluids at these depths, but also result in an increased strength of viscous deformation through the breakdown of weak hydrous phases (e.g., chlorite, glaucophane) and the growth of stronger minerals (e.g., garnet, omphacite, Ca-amphibole). Lastly, we present preliminary data on viscosity along warm subduction paths showing the locations of these dehydration pulses correlate with viscosity increases in mafic lithologies along the shallow forarc.</p>

scholarly journals Along‐Arc Heterogeneity in Local Seismicity across the Lesser Antilles Subduction Zone from a Dense Ocean‐Bottom Seismometer Network

2019 ◽  
Vol 91 (1) ◽  
pp. 237-247 ◽  
Author(s):  
Lidong Bie ◽  
Andreas Rietbrock ◽  
Stephen Hicks ◽  
Robert Allen ◽  
Jon Blundy ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Lesser Antilles ◽  
Seismogenic Zone ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Plate Interface ◽  
Local Seismicity ◽  
Slow Spreading ◽  
Lesser Antilles Arc

Abstract The Lesser Antilles arc is only one of two subduction zones where slow‐spreading Atlantic lithosphere is consumed. Slow‐spreading may result in the Atlantic lithosphere being more pervasively and heterogeneously hydrated than fast‐spreading Pacific lithosphere, thus affecting the flux of fluids into the deep mantle. Understanding the distribution of seismicity can help unravel the effect of fluids on geodynamic and seismogenic processes. However, a detailed view of local seismicity across the whole Lesser Antilles subduction zone is lacking. Using a temporary ocean‐bottom seismic network we invert for hypocenters and 1D velocity model. A systematic search yields a 27 km thick crust, reflecting average arc and back‐arc structures. We find abundant intraslab seismicity beneath Martinique and Dominica, which may relate to the subducted Marathon and/or Mercurius Fracture Zones. Pervasive seismicity in the cold mantle wedge corner and thrust seismicity deep on the subducting plate interface suggest an unusually wide megathrust seismogenic zone reaching ∼65  km depth. Our results provide an excellent framework for future understanding of regional seismic hazard in eastern Caribbean and the volatile cycling beneath the Lesser Antilles arc.

scholarly journals What’s down there? The structures, materials and environment of deep-seated slow slip and tremor

2021 ◽  
Vol 379 (2193) ◽  
pp. 20200218 ◽  
Author(s):  
Whitney M. Behr ◽  
Roland Bürgmann
Keyword(s):  
Subduction Zones ◽  
Source Region ◽  
Fluid Pressure ◽  
Plate Boundary ◽  
Seismogenic Zone ◽  
Slow Slip ◽  
Earthquake Dynamics ◽  
Plate Interface ◽  
Viscous Shear ◽  
Geophysical Imaging

Deep-seated slow slip and tremor (SST), including slow slip events, episodic tremor and slip, and low-frequency earthquakes, occur downdip of the seismogenic zone of numerous subduction megathrusts and plate boundary strike-slip faults. These events represent a fascinating and perplexing mode of fault failure that has greatly broadened our view of earthquake dynamics. In this contribution, we review constraints on SST deformation processes from both geophysical observations of active subduction zones and geological observations of exhumed field analogues. We first provide an overview of what has been learned about the environment, kinematics and dynamics of SST from geodetic and seismologic data. We then describe the materials, deformation mechanisms, and metamorphic and fluid pressure conditions that characterize exhumed rocks from SST source depths. Both the geophysical and geological records strongly suggest the importance of a fluid-rich and high fluid pressure habitat for the SST source region. Additionally, transient deformation features preserved in the rock record, involving combined frictional-viscous shear in regions of mixed lithology and near-lithostatic fluid pressures, may scale with the tremor component of SST. While several open questions remain, it is clear that improved constraints on the materials, environment, structure, and conditions of the plate interface from geophysical imaging and geologic observations will enhance model representations of the boundary conditions and geometry of the SST deformation process. This article is part of a discussion meeting issue ‘Understanding earthquakes using the geological record’.

Afterslip and slow slip events in the postseismic deformation of the 2016 Pedernales earthquake, Ecuador

2020 ◽  
Author(s):  
Frederique Rolandone ◽  
Jean-Mathieu nocquet ◽  
Patricia Mothes ◽  
Paul Jarrin ◽  
Mathilde Vergnolle
Keyword(s):  
Subduction Zones ◽  
Postseismic Deformation ◽  
Slow Slip ◽  
Aseismic Slip ◽  
Plate Interface ◽  
Slow Slip Events ◽  
North East ◽  
Rupture Area ◽  
Slip Event ◽  
Seismic Swarms

<p>In subduction zones, slip along the plate interface occurs in various modes including earthquakes, steady slip, and transient accelerated aseismic slip during either Slow Slip Events (SSE) or afterslip. We analyze continuous GPS measurements along the central Ecuador subduction segment to illuminate how the different slip modes are organized in space and time in the zone of the 2016 Mw 7.8 Pedernales earthquake. The early post-seismic period (1 month after the earthquake) shows large and rapid afterslip developing at discrete areas of the megathrust and a slow slip event remotely triggered (∼100 km) south of the rupture of the Pedernales earthquake. We find that areas of large and rapid early afterslip correlate with areas of the subduction interface that had hosted SSEs in years prior to the 2016 earthquake. Areas along the Ecuadorian margin hosting regular SSEs and large afterslip had a dominant aseismic slip mode that persisted throughout the earthquake cycle during several years and decades: they regularly experienced SSEs during the interseismic phase, they did not rupture during the 2016 Pedernales earthquake, they had large aseismic slip after it. Four years after the Pedernales earthquake, postseismic deformation is still on-going. Afterslip and SSEs are both involved in the postseimsic deformation. Two large aftershocks (Mw 6.7 & 6.8) occurred after the first month of postseismic deformation in May 18, and later in July 7 2016 two other large aftershocks (Mw 5.9 & 6.3) occurred, all were located north east of the rupture. They may have triggered their own postseismic deformation. Several seismic swarms were identified south and north of the rupture area by a dense network of seismic stations installed during one year after the Pedernales earthquakes, suggesting the occurrence of SSEs. Geodetically, several SSEs were detected during the postseismic deformation either in areas where no SSEs were detected previously, or in areas where regular seismic swarms and repeating earthquakes were identified. The SSEs may have been triggered by the stress increment due to aftershocks or due to afterslip.</p>

Triggering an Unexpected Earthquake in an Uncoupled Subduction Zone

2021 ◽  
Author(s):  
Kevin P. Furlong ◽  
Matthew W. Herman
Keyword(s):  
Subduction Zone ◽  
Plate Boundary ◽  
Strike Slip ◽  
Seismic Gap ◽  
Plate Interface ◽  
Thrust Faulting ◽  
Current Thinking ◽  
Abstract Submission ◽  
Geologic Record ◽  
Eastern Edge

<p>In the 1970’s, the Shumagin Islands region of the Alaska subduction zone was identified as a seismic gap expected to host a future great (Mw >8.0) earthquake. More recent geodetic data indicate this region is poorly coupled, and the geologic record shows little evidence of past large events - leading to current thinking of the “Shumagin Gap” as a region of low seismic hazard. From July to October 2020 (with aftershocks continuing through the time of this abstract submission in January), a series of earthquakes occurred in this region, potentially incompatible with this low-coupling interpretation. The initial Mw 7.8 plate interface thrust faulting earthquake on July 21st straddled the eastern edge of the Shumagin Gap, followed by an Mw 7.6 strike-slip earthquake on October 19th within the slab under the eastern side of the Shumagin Gap. Stress modeling indicates that this strike-slip earthquake is in fact favored if the Shumagin Gap has low coupling, whereas a highly coupled Shumagin Gap would inhibit that type and location of earthquake. The initial thrust earthquake and its afterslip significantly enhanced the strike-slip stress loading within the subducting slab, helping to trigger that event. We find that although regions such as the Shumagin Gap have a low seismogenic potential for plate interface thrusting, the existence of this decoupled region increases the potential for intra-plate strike-slip faulting in association with more typical subduction earthquakes on adjacent coupled segments of the plate boundary. Therefore, the seismic and tsunami potential near these uncoupled regions might be greater than previously thought.</p>

scholarly journals IODP Expedition 319, NanTroSEIZE Stage 2: First IODP Riser Drilling Operations and Observatory Installation Towards Understanding Subduction Zone Seismogenesis

2010 ◽  
Vol 10 ◽  
pp. 4-13 ◽  
Author(s):  
L. McNeill ◽  
D. Saffer ◽  
T. Byrne ◽  
E. Araki ◽  
S. Toczko ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Fault Zone ◽  
Hanging Wall ◽  
Plate Boundary ◽  
Fault System ◽  
Seismogenic Zone ◽  
Plate Boundaries ◽  
Forearc Basin ◽  
Drilling Operations

The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is a major drilling project designed to investigate fault mechanics and the seismogenic behavior of subduction zone plate boundaries. Expedition 319 is the first riser drilling operation within scientific ocean drilling. Operations included riser drilling at Site C0009 in the forearc basin above the plate boundary fault, non-riser drilling at Site C0010 across the shallow part of the megasplay fault system &ndash; which may slip during plate boundary earthquakes &ndash; and initial drilling at Site C0011 (incoming oceanic plate) for Expedition 322. At Site C0009, new methods were tested, including analysis of drill mud cuttings and gas, and <i>in situ</i> measurements of stress, pore pressure, and permeability. These results, in conjunction with earlier drilling, will provide (a) the history of forearc basin development (including links to growth of the megasplay fault system and modern prism), (b) the first <i>in situ</i> hydrological measurements of the plate boundary hanging wall, and (c) integration of <i>in situ</i> stress measurements (orientation and magnitude) across the forearc and with depth. A vertical seismic profile (VSP) experiment provides improved constraints on the deeper structure of the subduction zone. At Site C0010, logging-while-drilling measurements indicate significant changes in fault zone and hanging wall properties over short (< 5 km) along-strike distances, suggesting different burial and/or uplift history. The first borehole observatory instruments were installed at Site C0010 to monitor pressure and temperature within the megasplay fault zone, and methods of deployment of more complex observatory instruments were tested for future operations. <br><br> doi:<a href="http://dx.doi.org/10.2204/iodp.sd.10.01.2010" target="_blank">10.2204/iodp.sd.10.01.2010</a>

scholarly journals Effects of episodic slow slip on seismicity and stress near a subduction-zone megathrust

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Saeko Kita ◽  
Heidi Houston ◽  
Suguru Yabe ◽  
Sachiko Tanaka ◽  
Youichi Asano ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Fluid Pressure ◽  
Plate Boundary ◽  
Slow Slip ◽  
Plate Interface ◽  
B Values ◽  
Megathrust Earthquakes ◽  
Cyclic Processes ◽  
Stress Orientations ◽  
Oceanic Slab

AbstractSlow slip phenomena deep in subduction zones reveal cyclic processes downdip of locked megathrusts. Here we analyze seismicity within a subducting oceanic slab, spanning ~50 major deep slow slip with tremor episodes over 17 years. Changes in rate, b-values, and stress orientations of in-slab seismicity are temporally associated with the episodes. Furthermore, although stress orientations in the slab below these slow slips may rotate slightly, in-slab orientations 20–50 km updip from there rotate farther, suggesting that previously-unrecognized transient slow slip occurs on the plate interface updip. We infer that fluid pressure propagates from slab to interface, promoting episodes of slow slip, which break mineral seals, allowing the pressure to propagate tens of km further updip along the interface where it promotes transient slow slips. The proposed methodology, based primarily on in-slab seismicity, may help monitor plate boundary conditions and slow slip phenomena, which can signal the beginning stages of megathrust earthquakes.

Subduction zone seismo-dynamics: how to bridge the gap between long-term subduction dynamics and megathrust seismicity?

2021 ◽  
Author(s):  
Adam Beall ◽  
Fabio A. Capitanio ◽  
Ake Fagereng ◽  
Ylona van Dinther
Keyword(s):  
Stress State ◽  
Subduction Zone ◽  
Subduction Zones ◽  
Large Scale ◽  
Large Earthquake ◽  
Force Balance ◽  
Mantle Flow ◽  
Plate Interface ◽  
Plate Motions

&lt;p&gt;The largest and most devastating earthquakes on Earth occur along subduction zones. Here, long-term plate motions are accommodated in cycles of strain accumulation and release. Episodic strain release occurs by mechanisms ranging from rapid earthquakes to slow-slip and quasi-static creep along the plate interface. Slip styles can vary between and within subduction zones, though it is unclear what controls margin-scale variability. Current approaches to seismo-tectonics primarily relate the stress state and seismogenesis at subduction margins to interface material properties and plate kinematics, constrained by recorded seismic slip, GPS motions and integrated strain. At larger spatio-temporal scales, significant progress has been made towards the understanding of subduction dynamics and emerging self-consistent plate motions, tectonics and stress coupling at plate margins. The margin stress state is ultimately linked to the force balance arising from interactions between the slab, mantle flow and upper plate. These mantle and lithosphere dynamics are thus expected to govern the tectonic regimes under which seismicity occurs. It remains unclear how these longer- and shorter-term perspectives can be reconciled. We review the aspects of large-scale subduction dynamics that control tectonic loading at plate margins, discuss possible influences on the stress state of the plate interface, and summarise recent advances in integrating the earthquake cycle and large-scale dynamics. It is plausible that variations in large-scale subduction dynamics could systematically influence seismicity, though it remains unclear to what degree this interplay occurs directly through the plate interface stress state and/or indirectly, corresponding to variation of other subduction zone characteristics. While further constraints of the geodynamic controls on the nature of the plate interface and their incorporation into probabilistic earthquake models is required, their ongoing development holds promise for an improved understanding of the global variation of large earthquake occurrence and their associated risk.&lt;/p&gt;

The rule of thumb for inferring plate coupling status based on the mantle lithospheric buoyancy

2020 ◽  
Author(s):  
Chung-Liang Lo ◽  
Wen-Bin Doo ◽  
Shu-Kun Hsu
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Plate Boundary ◽  
Coupling Factor ◽  
Potential Hazard ◽  
The Status ◽  
Southern Central ◽  
Plate Coupling ◽  
The Difference

&lt;p&gt;The subduction zone is a convergent plate boundary, and where most seismic activity is concentrated and megathrust may occur. To evaluate the potential hazard in subduction zones always relates to the plate coupling status. From previous studies, the status of plate coupling between plates can be reflected by the vibration of the buoyancy of mantle lithosphere (Hm). As far as the respective plate coupling states are concerned, more than a dozen Hm profiles across different subduction zones have been successfully verified. It is normally to determine the coupling status depending on the Hm vibration without manifest definition. We therefore propose a method to estimate the plate coupling factor (pcf) quantitatively. The pcf is defined as the difference of the Hm caused by the respective subduction and overriding plates between the distances where Hm deviated from the normal lithospheric Hm value across the plate boundary. The collected Hm profiles are calculated by the proposed method, the results show that the pcf value is corresponding well to the plate coupling status in the respective subduction zone. The small pcf is for strong plate coupling, such as the northern Sumatra and the southern central Andes subduction zones, while the large pcf is for weak coupling, such as the Calabria and the northern Manila subduction zones. The calculation of pcf is a feasible solution for determination of plate coupling status, but more Hm profiles across subduction zones will help the estimation more reliable.&lt;/p&gt;

scholarly journals Slow slip source characterized by lithological and geometric heterogeneity

2020 ◽  
Vol 6 (13) ◽  
pp. eaay3314 ◽  
Author(s):  
Philip M. Barnes ◽  
Laura M. Wallace ◽  
Demian M. Saffer ◽  
Rebecca E. Bell ◽  
Michael B. Underwood ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Source Region ◽  
Significant Proportion ◽  
Plate Motion ◽  
Direct Access ◽  
Slow Slip ◽  
Plate Interface ◽  
Slow Slip Events ◽  
Geophysical Imaging

Slow slip events (SSEs) accommodate a significant proportion of tectonic plate motion at subduction zones, yet little is known about the faults that actually host them. The shallow depth (<2 km) of well-documented SSEs at the Hikurangi subduction zone offshore New Zealand offers a unique opportunity to link geophysical imaging of the subduction zone with direct access to incoming material that represents the megathrust fault rocks hosting slow slip. Two recent International Ocean Discovery Program Expeditions sampled this incoming material before it is entrained immediately down-dip along the shallow plate interface. Drilling results, tied to regional seismic reflection images, reveal heterogeneous lithologies with highly variable physical properties entering the SSE source region. These observations suggest that SSEs and associated slow earthquake phenomena are promoted by lithological, mechanical, and frictional heterogeneity within the fault zone, enhanced by geometric complexity associated with subduction of rough crust.

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