scholarly journals IODP Expedition 338: NanTroSEIZE Stage 3: NanTroSEIZE plate boundary deep riser 2

2014 ◽  
Vol 17 ◽  
pp. 1-12 ◽  
Author(s):  
G. F. Moore ◽  
K. Kanagawa ◽  
M. Strasser ◽  
B. Dugan ◽  
L. Maeda ◽  
...  
Keyword(s):  
Fault Zone ◽  
Early Stage ◽  
Plate Boundary ◽  
Seismogenic Zone ◽  
Fault Mechanics ◽  
Submarine Landslides ◽  
State Variables ◽  
Drilling Mud ◽  
Forearc Basin ◽  
Rock Composition

Abstract. The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is designed to investigate fault mechanics and seismogenesis along a subduction megathrust, with objectives that include characterizing fault slip, strain accumulation, fault and wall rock composition, fault architecture, and state variables throughout an active plate boundary system. Integrated Ocean Drilling Program (IODP) Expedition 338 was planned to extend and case riser Hole C0002F from 856 to 3600 meters below the seafloor (m b.s.f.). Riser operations extended the hole to 2005.5 m b.s.f., collecting logging-while-drilling (LWD) and measurement-while-drilling, mud gas, and cuttings data. Results reveal two lithologic units within the inner wedge of the accretionary prism that are separated by a prominent fault zone at ~ 1640 m b.s.f. Due to damage to the riser during unfavorable winds and strong currents, riser operations were suspended, and Hole C0002F left for re-entry during future riser drilling operations. Contingency riserless operations included coring at the forearc basin site (C0002) and at two slope basin sites (C0021 and C0022), and LWD at one input site (C0012) and at three slope basin sites (C0018, C0021 and C0022). Cores and logs from these sites comprehensively characterize the alteration stage of the oceanic basement input to the subduction zone, the early stage of Kumano Basin evolution, gas hydrates in the forearc basin, and recent activity of the shallow megasplay fault zone system and associated submarine landslides.

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>

Weak at what scale? Insights from a late interseismic interplate fault

2021 ◽  
Author(s):  
Carolyn Boulton ◽  
Catriona Menzies ◽  
Virginia Toy ◽  
Ludmila Adam ◽  
John Townend ◽  
...  
Keyword(s):  
Fault Zone ◽  
Hanging Wall ◽  
Damage Zone ◽  
Plate Boundary ◽  
Seismogenic Zone ◽  
Low Permeability ◽  
Temperature Sensitive ◽  
Fault Rock ◽  
Alpine Fault ◽  
Brittle Ductile Transition

&lt;p&gt;The central section of the Alpine Fault accommodates a majority (~75%) of the total relative Pacific-Australian plate boundary motion on a single structure. For strain localization to occur to such an extent, the Alpine Fault must accommodate deformation at spatially and temporally averaged work rates that are lower than those required by hanging wall and footwall structures. Exhumation of a complete fault rock sequence (mylonites-cataclasites-gouges) from ~35 km depth in &lt;5 million years provides us with an unparalleled opportunity to identify the weakening mechanisms underpinning the fault&amp;#8217;s remarkable efficiency. We summarize the results of experimental, geochemical, geophysical, seismological, and geological research facilitated by the Deep Fault Drilling Project (DFDP).&lt;/p&gt;&lt;p&gt;Three main factors promote crustal-scale weakness on Alpine Fault: (1) high heat flow associated with rapid exhumation results in a shallow frictional-viscous transition at 8-10 km depth. In turn, temperature-sensitive creep (initially crystal-plasticity with an increasing contribution from grain size sensitive mechanisms during exhumation) can accommodate deformation at strain rates on the order of, and episodically higher than, 10&lt;sup&gt;&amp;#8211;12&lt;/sup&gt;s&lt;sup&gt;&amp;#8211;1&lt;/sup&gt;across a broad portion of the fault zone (from ~8 to 35 km depth). (2) Above the frictional-viscous transition, cataclastic processes associated with quasiperiodic large-magnitude earthquakes have permanently reduced the elastic moduli of damage zone rocks; and (3) cataclastic processes, combined with fluid-rock interactions, have formed low-permeability principal slip zone gouges and cataclasites. The near-ubiquitous presence of juxtaposed, low-permeability fault core gouges and cataclasites promotes dynamic (coseismic) weakening mechanisms such as thermal pressurization.&lt;/p&gt;&lt;p&gt;Clay mineral alteration reactions are commonly thought to result in fault zone weakening through a reduction in the static coefficient of friction, but fluid-rock interactions on the central Alpine Fault largely result in the precipitation of frictionally strong minerals such as calcite and, locally, K-feldspar. Although relatively narrow in down-dip extent, the brittle seismogenic zone of the central Alpine Fault is not misoriented with respect to the maximum principal stress when a full 3D stress analysis is performed. Moreover, the fault comprises frictionally strong gouges and cataclasites that can sustain high differential stresses. Combined, these factors have important implications for estimating dynamic stress drops and the extent to which future earthquake ruptures may propagate beneath the brittle-ductile transition, thereby increasing moment magnitude.&lt;/p&gt;

Effects of heterogeneity on frictional-viscous deformation and the depth-extent of the seismogenic zone

2021 ◽  
Author(s):  
Ake Fagereng ◽  
Adam Beall
Keyword(s):  
Shear Stress ◽  
Yield Strength ◽  
Fault Zone ◽  
Fluid Pressure ◽  
Local Stress ◽  
Seismogenic Zone ◽  
Depth Range ◽  
Viscous Deformation ◽  
Viscosity Contrast ◽  
Depth Extent

&lt;p&gt;Current conceptual fault models define a seismogenic zone, where earthquakes nucleate, characterised by velocity-weakening fault rocks in a dominantly frictional regime. The base of the seismogenic zone is commonly inferred to coincide with a thermally controlled onset of velocity-strengthening slip or distributed viscous deformation. The top of the seismogenic zone may be determined by low-temperature diagenetic processes and the state of consolidation and alteration. Overall, the seismogenic zone is therefore described as bounded by transitions in frictional and rheological properties. These properties are relatively well-determined for monomineralic systems and simple, planar geometries; but, many exceptions, including deep earthquakes, slow slip, and shallow creep, imply processes involving compositional, structural, or environmental heterogeneities. We explore how such heterogeneities may alter the extent of the seismogenic zone.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;We consider mixed viscous-frictional deformation and suggest a simple rule of thumb to estimate the role of heterogeneities by a combination of the viscosity contrast within the fault, and the ratio between the bulk shear stress and the yield strength of the strongest fault zone component. In this model, slip behaviour can change dynamically in response to stress and strength variations with depth and time. We quantify the model numerically, and illustrate the idea with a few field-based examples: 1) earthquakes within the viscous regime, deeper than the thermally-controlled seismogenic zone, can be triggered by an increase in the ratio of shear stress to yield strength, either by increased fluid pressure or increased local stress; 2) there is commonly a depth range of transitional behaviour at the base of the seismogenic zone &amp;#8211; the thickness of this zone increases markedly with increased viscosity contrast within the fault zone; and 3) fault zone weakening by phyllosilicate growth and foliation development increases viscosity ratio and decreases bulk shear stress, leading to efficient, stable, fault zone creep. These examples are not new interpretations or observations, but given the substantial complexity of heterogeneous fault zones, we suggest that a simplified, conceptual model based on basic strength and stress parameters is useful in describing and assessing the effect of heterogeneities on fault slip behaviour.&amp;#160; &amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&lt;/p&gt;

scholarly journals Fault Zone Guided Wave generation on the locked, late interseismic Alpine Fault, New Zealand

2021 ◽  
Author(s):  
JD Eccles ◽  
AK Gulley ◽  
PE Malin ◽  
CM Boese ◽  
John Townend ◽  
...  
Keyword(s):  
Fault Zone ◽  
Plate Boundary ◽  
Guided Wave ◽  
S Wave ◽  
Low Velocity ◽  
Catchment Scale ◽  
Near Surface ◽  
Low Velocity Zone ◽  
Alpine Fault ◽  
Velocity Zone

© 2015. American Geophysical Union. All Rights Reserved. Fault Zone Guided Waves (FZGWs) have been observed for the first time within New Zealand's transpressional continental plate boundary, the Alpine Fault, which is late in its typical seismic cycle. Ongoing study of these phases provides the opportunity to monitor interseismic conditions in the fault zone. Distinctive dispersive seismic codas (~7-35Hz) have been recorded on shallow borehole seismometers installed within 20m of the principal slip zone. Near the central Alpine Fault, known for low background seismicity, FZGW-generating microseismic events are located beyond the catchment-scale partitioning of the fault indicating lateral connectivity of the low-velocity zone immediately below the near-surface segmentation. Initial modeling of the low-velocity zone indicates a waveguide width of 60-200m with a 10-40% reduction in S wave velocity, similar to that inferred for the fault core of other mature plate boundary faults such as the San Andreas and North Anatolian Faults.

Recent and active deformation in the North Evia domain, a diffuse plate boundary between Eurasia and Aegean plates in the Western termination of the North Anatolian Fault. 

2021 ◽  
Author(s):  
Fabien Caroir ◽  
Frank Chanier ◽  
Virginie Gaullier ◽  
Julien Bailleul ◽  
Agnès Maillard-Lenoir ◽  
...  
Keyword(s):  
Fault Zone ◽  
Plate Boundary ◽  
Fault Zones ◽  
North Anatolian Fault ◽  
Fault System ◽  
Eurasian Plate ◽  
Slip Rates ◽  
The North ◽  
South West ◽  
North Aegean

&lt;p&gt;The Anatolia-Aegean microplate is currently extruding toward the South and the South-West. This extrusion is classically attributed to the southward retreat of the Aegean subduction zone together with the northward displacement of the Arabian plate. The displacement of Aegean-Anatolian block relative to Eurasia is accommodated by dextral motion along the North Anatolian Fault (NAF), with current slip rates of about 20 mm/yr. The NAF is propagating westward within the North Aegean domain where it gets separated into two main branches, one of them bordering the North Aegean Trough (NAT). This particular context is responsible for dextral and normal stress regimes between the Aegean plate and the Eurasian plate. South-West of the NAT, there is no identified major faults in the continuity of the NAF major branch and the plate boundary deformation is apparently distributed within a wide domain. This area is characterised by slip rates of 20 to 25 mm/yr relative to Eurasian plate but also by clockwise rotation of about 10&amp;#176; since ca 4 Myr. It constitutes a major extensional area involving three large rift basins: the Corinth Gulf, the Almiros Basin and the Sperchios-North Evia Gulf. The latter develops in the axis of the western termination of the NAT, and is therefore a key area to understand the present-day dynamics and the evolution of deformation within this diffuse plate boundary area.&lt;/p&gt;&lt;p&gt;Our study is mainly based on new structural data from field analysis and from very high resolution seismic reflexion profiles (Sparker 50-300 Joules) acquired during the WATER survey in July-August 2017 onboard the R/V &amp;#8220;T&amp;#233;thys II&amp;#8221;, but also on existing data on recent to active tectonics (i.e. earthquakes distribution, focal mechanisms, GPS data, etc.). The results from our new marine data emphasize the structural organisation and the evolution of the deformation within the North Evia region, SW of the NAT.&lt;/p&gt;&lt;p&gt;The combination of our structural analysis (offshore and onshore data) with available data on active/recent deformation led us to define several structural domains within the North Evia region, at the western termination of the North Anatolian Fault. The North Evia Gulf shows four main fault zones, among them the Central Basin Fault Zone (CBFZ) which is obliquely cross-cutting the rift basin and represents the continuity of the onshore Kamena Vourla - Arkitsa Fault System (KVAFS). Other major fault zones, such as the Aedipsos Politika Fault System (APFS) and the Melouna Fault Zone (MFZ) played an important role in the rift initiation but evolved recently with a left-lateral strike-slip motion. Moreover, our seismic dataset allowed to identify several faults in the Skopelos Basin including a large NW-dipping fault which affects the bathymetry and shows an important total vertical offset (&gt;300m). Finally, we propose an update of the deformation pattern in the North Evia region including two lineaments with dextral motion that extend southwestward the North Anatolian Fault system into the Oreoi Channel and the Skopelos Basin. Moreover, the North Evia Gulf domain is dominated by active N-S extension and sinistral reactivation of former large normal faults.&lt;/p&gt;

Physical and chemical strain-hardening during faulting in poorly lithified sandstone: The role of kinematic stress field and selective cementation

2019 ◽  
Vol 132 (5-6) ◽  
pp. 1183-1200 ◽  
Author(s):  
Mattia Pizzati ◽  
Fabrizio Balsamo ◽  
Fabrizio Storti ◽  
Paola Iacumin
Keyword(s):  
Stress Field ◽  
Strain Hardening ◽  
Fault Zone ◽  
Deformation Band ◽  
Early Stage ◽  
Damage Zone ◽  
Isotope Analysis ◽  
Deformation Bands ◽  
Multidisciplinary Study ◽  
Diagenetic Evolution

Abstract In this work, we report the results of a multidisciplinary study describing the structural architecture and diagenetic evolution of the Rocca di Neto extensional fault zone developed in poorly lithified sandstones of the Crotone Basin, Southern Italy. The studied fault zone has an estimated displacement of ∼90 m and consists of: (1) a low-deformation zone with subsidiary faults and widely spaced deformation bands; (2) an ∼10-m-wide damage zone, characterized by a dense network of conjugate deformation bands; (3) an ∼3-m-wide mixed zone produced by tectonic mixing of sediments with different grain size; (4) an ∼1-m-wide fault core with bedding transposed into foliation and ultra-comminute black gouge layers. Microstructural investigations indicate that particulate flow was the dominant early-stage deformation mechanism, while cataclasis became predominant after porosity loss, shallow burial, and selective calcite cementation. The combination of tectonic compaction and preferential cementation led to a strain-hardening behavior inducing the formation of “inclined conjugate deformation band sets” inside the damage zone, caused by the kinematic stress field associated with fault activity. Conversely, conjugate deformation band sets with a vertical bisector formed outside the damage zone in response to the regional extensional stress field. Stable isotope analysis helped in constraining the diagenetic environment of deformation, which is characterized by mixed marine-meteoric signature for cements hosted inside the damage zone, while it progressively becomes more meteoric moving outside the fault zone. This evidence supports the outward propagation of fault-related deformation structures in the footwall damage zone.

Seismotectonics of the Ionian-Akarnania Block (IAB) and Western Greece deduced from a local seismic deployment.

2020 ◽  
Author(s):  
Antoine Haddad ◽  
Athanassios Ganas ◽  
Ioannis Kassaras ◽  
Matteo Lupi
Keyword(s):  
Fault Zone ◽  
Velocity Model ◽  
Focal Mechanisms ◽  
Seismogenic Zone ◽  
The South ◽  
S Wave ◽  
North West ◽  
The North ◽  
Short Period ◽  
Western Greece

&lt;p&gt;From July 2016 to May 2017, we deployed a local seismic network composed of 15 short-period seismic stations to investigate the ongoing seismotectonic deformation of Western Greece with emphasis on the region between Ambrakikos Gulf (to the north) and Kyparissia (to the south). The network was deployed to investigate the behavior of key crustal blocks in western Greece, such as the Ionian-Akarnania Block (IAB).&lt;/p&gt;&lt;p&gt;After applying automatic P- and S- wave phase picking we located 1200 local earthquakes using HypoInverse and constrained five 1D velocity model by applying the error minimization technique. Events were relocated using HypoDD and 76&amp;#160; focal mechanisms were computed for events with magnitudes down to M&lt;sub&gt;L&lt;/sub&gt; 2.3 using first motion polarities.&lt;/p&gt;&lt;p&gt;We combined the calculated focal mechanisms and the relocated seismicity to shed light on the IAB block boundaries. Three boundaries highlighted by previous studies were also evidenced :&lt;/p&gt;&lt;p&gt;-The north-west margin of the block, the Cephalonia Transform Fault, Europe&amp;#8216;s most active fault. NW-striking dextral strike-slip motion was recognized for this fault near the Gulf of Myrtos and the town of Fiskardo.&lt;/p&gt;&lt;p&gt;- The south-east margin is the Movri-Amaliada right-lateral Fault Zone, activated during the Movri Mt. M&lt;sub&gt;w&lt;/sub&gt; 6.4 earthquake sequence.&lt;/p&gt;&lt;p&gt;- The Ambrakikos Gulf (a young E-W rift) and the NW-striking left-lateral Katouna-Stamna Fault zone depict the north and north-eastern margins of the IAB block.&lt;/p&gt;&lt;p&gt;Seismicity lineaments and focal mechanisms define theKyllini-Cephalonia left-lateral fault, which is also highlighted by bathymetry data. We interpret this fault as the south-western margin of IAB separating an aseismic area observed between Cephalonia and Akarnania from a seismogenic zone north of Zakynthos Island and bridging NW Peloponnese with Cephalonia.&lt;/p&gt;

Quantifying effects of laboratory-simulated diagenetic sediment lithification on frictional slip behavior

2020 ◽  
Author(s):  
Matt Ikari ◽  
Andre Hüpers
Keyword(s):  
Plate Boundary ◽  
Seismogenic Zone ◽  
Low Grade ◽  
Depth Range ◽  
Experimental Conditions ◽  
Frictional Behavior ◽  
Frictional Properties ◽  
Porosity Reduction ◽  
Fault Gouges ◽  
Frictional Slip

&lt;p&gt;On major plate-boundary fault zones, it is generally observed that large-magnitude earthquakes tend to nucleate within a discrete depth range in the crust known as the seismogenic zone.&amp;#160; This is generally explained by the contrast between frictionally stable, velocity strengthening sediments at shallow depths and lithified, velocity-weakening rocks at seismogenic (10&amp;#8217;s of km) depth. Thus, it is hypothesized that diagenetic and low-grade metamorphic processes are responsible for the development of velocity-weakening frictional behavior in sediments that make up fault gouges.&amp;#160; Previous laboratory studies comparing the frictional properties of intact rocks and powdered versions of the same rocks generally support this hypothesis, however controlling lithification in the laboratory and systematically quantifying frictional behavior as a function of lithification and remains a challenge.&lt;/p&gt;&lt;p&gt;Here, we simulate the lithification process in the laboratory by using mixtures of halite and shale powders with halite-saturated brine, which we consolidate under 10 MPa normal stress and subsequently desiccate.&amp;#160; The desiccation allows precipitation of halite as cement, creating synthetic rocks.&amp;#160; We vary the proportion of salt to shale in our samples, which we use as a proxy for degree of lithification.&amp;#160; We measure the frictional properties of our lithified samples, and equivalent powdered versions of these samples, with velocity-step tests in the range 10&lt;sup&gt;-7&lt;/sup&gt; &amp;#8211; 3x10&lt;sup&gt;-5&lt;/sup&gt; m/s.&amp;#160; We quantify lithification by two methods: (1) direct measurement of cohesion, and (2) measuring the porosity reduction of lithified samples compared to powders.&amp;#160; Using these measurements, we systematically investigate the relationship between lithification and frictional slip behavior.&lt;/p&gt;&lt;p&gt;We observe that powdered samples of every halite-shale proportion exhibits predominantly velocity-strengthening friction, whereas lithified samples exhibit a combination of velocity strengthening and significant velocity weakening when halite constitutes at least 30 wt% of the sample.&amp;#160; Larger velocity weakening generally coincides with friction coefficients of &gt; 0.62, cohesion of &gt; ~1 MPa, and porosity reduction of &gt; ~50 vol%.&amp;#160; Although none of our lithified samples exhibit strictly velocity-weakening friction, this is consistent with the frictional behavior of pure halite under our experimental conditions.&amp;#160; Scanning electron microscopy images do not show any clear characteristics attributable to velocity-weakening, but did reveal that the shear surfaces for powders tends to exhibit small cracks not seen in the lithified sample shear surfaces.&amp;#160; These results suggest that lithification via cementation and porosity loss may facilitate slip instability, but that microstructural indicators are subtle.&lt;/p&gt;

Sign in / Sign up

Export Citation Format

Share Document