scholarly journals The Sumatra subduction zone: A case for a locked fault zone extending into the mantle

2004 ◽  
Vol 109 (B10) ◽  
Author(s):  
Martine Simoes ◽  
Jean Philippe Avouac ◽  
Rodolphe Cattin ◽  
Pierre Henry
Keyword(s):  
Subduction Zone ◽  
Fault Zone ◽  
Locked Fault

Continual interaction between the Minahassa subduction interface and the Palu-Koro strike-slip fault in Sulawesi, Indonesia.

2020 ◽  
Author(s):  
Nicolai Nijholt ◽  
Wim Simons ◽  
Riccardo Riva
Keyword(s):  
Subduction Zone ◽  
Fault Zone ◽  
Slip Rate ◽  
Strike Slip ◽  
Strike Slip Fault ◽  
Model Calculations ◽  
Transient Deformation ◽  
Subduction Earthquake ◽  
Bay Area ◽  
Gnss Velocities

<p>Two major fault systems host M<sub>w</sub>>7 earthquakes in Central and Northern Sulawesi, Indonesia: the Minahassa subduction interface and the Palu-Koro strike-slip fault. The Celebes Sea oceanic lithosphere subducts beneath the north arm of Sulawesi at the Minahassa subduction zone. At the western termination of the Minahassa subduction zone, it connects to the left-lateral Palu-Koro strike-slip fault zone. This fault strikes onshore at Palu Bay and then crosses Sulawesi. Interseismic GNSS velocities indicate that the Palu-Koro fault zone accommodates about 4 cm/yr of relative motion in the Palu Bay area, with a ~10 km locking depth. This shallowly locked segment of the Palu-Koro fault around the Palu Bay area ruptured during the devastating, tsunami-generating, 2018 M<sub>w</sub>7.5 Palu earthquake. This complex event highlights the high seismic hazard for the island of Sulawesi.</p><p>We have a >20-year record of GNSS velocities on Sulawesi, where the densest cluster of monument sites surrounds the Palu-Koro fault, specifically around Palu Bay, whereas the rest of the island is less densely covered. High quality estimates of interseismic velocities reveal second-order complex patterns of transient deformation in the wake of major earthquakes: the velocities in northern Sulawesi and around the Palu-Koro fault do not follow their interseismic trends after a major subduction earthquake has occurred, for several years after the event. This effect of transient deformation reaches more than 400km away from the epicentre of the major earthquakes. Surprisingly, a deviation from the background slip rate on the Palu-Koro fault is not accompanied by a deviation from the background (micro)seismic activity.</p><p>We construct a 3D numerical model based on the structural and seismological data in the Sulawesi region. We investigate the post-seismic relaxation pattern from a subduction earthquake and determine whether the slip rate on the Palu-Koro fault changes due to this earthquake through forward model calculations. With a modelling focus on the 1996 M<sub>w</sub>7.9 and 2008 M<sub>w</sub>7.4 earthquakes that ruptured the Minahassa subduction interface, this study outlines the triggering of transient deformation and continual interaction between the Minahassa subduction interface and the Palu-Koro strike-slip fault.</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>

Sounds of the deep subduction zone plumbing system: modeling non-volcanic tremor activity in a fault-valve, pore-pressure diffusive system

2020 ◽  
Author(s):  
Gaspard Farge ◽  
Nikolai Shapiro ◽  
Claude Jaupart ◽  
Édouard Kaminski
Keyword(s):  
Transport Properties ◽  
Pore Pressure ◽  
Subduction Zone ◽  
Fault Zone ◽  
Subduction Zones ◽  
Low Frequency ◽  
Volcanic Tremor ◽  
Stable Conditions ◽  
Slow Earthquakes ◽  
Diffusive System

&lt;p&gt;The activity of slow-earthquakes in subduction zones have been closely linked to fluid circulation processes &amp;#8212; like hydro fracturation and pore-pressure pulses &amp;#8212; on the one hand by geological observations and on the other hand by slow-earthquake triggering and interaction models. In deep fault zone environments, where slow slip events and various regimes of tremor are observed, fluids coming from metamorphic dehydration of slab sediments are channeled towards the surface. Geological observations indicate that fluid transport conditions vary significantly on short time scales, and along dip, strike and width of the fault zone. In homogeneously permeable systems where fluids transit under stable conditions, pore-pressure can be described by a diffusion equation. We use a time and space bimodal description of the transport properties to model a tremor generating, permeable fault zone. Thin zones of low permeability acting as valves are distributed along the 1D channel with a higher background permeability. When a threshold pore-pressure differential is reached, the valve permeability is brought to background levels, until the barrier is healed and closes again. In this model, the opening of a valve occurs at the same time as the source of a low-frequency earthquake (LFE) is triggered. In such a set up, sources interact uniquely due to the channeling of stress through pore-pressure diffusion, and the interaction characteristics in time/space are described in the framework of a diffusive system. When the number of sources is high, the model can reproduce clustering behaviours observed for LFE activity in subduction zones. The transition from a Poisson process description of seismicity to highly clustered, cascading events is governed by the source interaction distances, directly relating to the transport properties of the medium. In time, such a model is meant to diagnose the transport conditions in a subduction zone or a magmatic system, provided that it can be characterized by clustering statistics on the low-frequency seismicity it generates.&lt;/p&gt;

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