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The Seismogenic Zone of Subduction Thrust Faults

The Seismogenic Zone of Subduction Thrust Faults

Timothy H. Dixon
J. Casey Moore
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    The Seismogenic Zone of Subduction Thrust Faults
    Book Description:

    Subduction zones, one of the three types of plate boundaries, return Earth's surface to its deep interior. Because subduction zones are gently inclined at shallow depths and depress Earth's temperature gradient, they have the largest seismogenic area of any plate boundary. Consequently, subduction zones generate Earth's largest earthquakes and most destructive tsunamis. As tragically demonstrated by the Sumatra earthquake and tsunami of December 2004, these events often impact densely populated coastal areas and cause large numbers of fatalities.

    While scientists have a general understanding of the seismogenic zone, many critical details remain obscure. This volume attempts to answer such fundamental concerns as why some interplate subduction earthquakes are relatively modest in rupture length (greater than 100 km) while others, such as the great (M greater than 9) 1960 Chile, 1964 Alaska, and 2004 Sumatra events, rupture along 1000 km or more. Contributors also address why certain subduction zones are fully locked, accumulating elastic strain at essentially the full plate convergence rate, while others appear to be only partially coupled or even freely slipping; whether these locking patterns persist through the seismic cycle; and what is the role of sediments and fluids on the incoming plate.

    Nineteen papers written by experts in a variety of fields review the most current lab, field, and theoretical research on the origins and mechanics of subduction zone earthquakes and suggest further areas of exploration. They consider the composition of incoming plates, laboratory studies concerning sediment evolution during subduction and fault frictional properties, seismic and geodetic studies, and regional scale deformation. The forces behind subduction zone earthquakes are of increasing environmental and societal importance.

    eISBN: 978-0-231-51201-5
    Subjects: General Science, Geology, Aquatic Sciences, Environmental Science

Table of Contents

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  1. Front Matter
    (pp. i-iv)
  2. Table of Contents
    (pp. v-vii)
  3. Preface
    (pp. viii-x)
  4. PART I Introduction

    • 1 The Seismogenic Zone of Subduction Thrust Faults: Introduction
      (pp. 2-14)
      Timothy H. Dixon and J. Casey Moore

      Subduction zones such as the circum-Pacific “ring of fire” are characterized by a dipping, relatively narrow (~100–200 km width) and shallow (<50 km depth) surface capable of generating large (M > 7) and great (M > 8) earthquakes. This surface represents the interface between subducting and overriding plates and is often termed the seismogenic zone (fig. 1.1). For reasons that are fundamental to the subduction process, including depression of isotherms and consequent broadening of that part of the plate interface where seismic processes can occur, these zones generate Earth’s largest earthquakes and most destructive tsunamis. The earthquakes and subsequent tsunamis often...

    • 2 The Seismogenic Zone of Subduction Thrust Faults: What We Know and Don’t Know
      (pp. 15-40)
      R. D. Hyndman

      Most of the world’s great earthquakes (M ≥ 8), many intermediate magnitude events, and most large tsunamis are generated by rupture on the “seismogenic zone” of subduction thrust faults (fig. 2.1). In this discussion, I outline some of important seismic characteristics of subduction thrust faults and their physical associations; what I think we know and what we don’t know. Most of what we know has come from remote observation. There are no boreholes as yet into the seismogenic portion of subduction thrusts, although there has been drilling through the updip aseismic portion by the Ocean Drilling Program [e.g., Moore et...

  5. PART II The Incoming Plate

    • 3 Sediment Inputs to Subduction Zones: Why Lithostratigraphy and Clay Mineralogy Matter
      (pp. 42-85)
      Michael B. Underwood

      One of the more ambitious goals of the Seismogenic Zone Experiment (SEIZE) is to separate the effects of intrinsic frictional strength (i.e., gouge versus wall rock) from the effects of gradual or transient increases in pore pressure as they collectively modulate the downdip evolution of plate-boundary faults. As subduction proceeds, sedimentary strata on the downgoing plate change progressively in the downdip direction. These transformations create a fundamental difference between subduction megathrusts and transform boundaries (e.g., the San Andreas fault). The basal décollement marks the structural contact between domains of offscraped and underthrust strata [Moore, 1989]. Presumably, the faults nucleate within,...

    • 4 The Thermal State of 18–24 Ma Upper Lithosphere Subducting Below the Nicoya Peninsula, Northern Costa Rica Margin
      (pp. 86-122)
      M. Hutnak, A. T. Fisher, C. A. Stein, R. Harris, K. Wang, E. Silver, G. Spinelli, M. Pfender, H. Villinger, R. MacKnight, P. Costa Pisani, H. DeShon and C. Diamente

      The thermal state of subducting oceanic plates influences melting conditions in the overlying mantle wedge, the extent of sediment dewatering associated with mineralogical and rheological transitions, the occurrence of gas hydrates along the active margin, and the nature of tectonic and seismic processes at depth [e.g., Fisher et al., 2003b; Gaetani and Grove, 1998; Hyndman and Wang, 1993; Ruppel and Kinoshita, 2000; Saffer and Marone, 2003; Stein, 2003; Zhao et al., 1997]. Determining thermal conditions within subduction zones is difficult because drilling to necessary depths poses severe technical challenges, and seafloor thermal data collected on the margin are typically influenced...

    • 5 Influence of Subducting Topography on Earthquake Rupture
      (pp. 123-146)
      Susan L. Bilek

      Early definitions of asperities go back to Amonton, who proposed that static friction on a fault relates to the overall roughness of the fault surface. Increased roughness on the surface may be caused by increased occurrence of protrusions on the surface. He defined asperities as welded contacts along the fault. Early asperity models for earthquakes were developed using results from laboratory rock friction experiments [Byerlee, 1967; Scholz and Engelder, 1976]. These models suggest that faults are held together by high strength contacts, or Amonton’s asperities. Stresses at the asperities were typically higher than at other portions of the fault. The...

  6. PART III Convergent Margin Structure, Fluids and Subduction Thrust Evolution

    • 6 Pore Pressure and Fluid Flow in the Northern Barbados Accretionary Complex: A Synthesis
      (pp. 148-170)
      Barbara A. Bekins and Elizabeth J. Screaton

      At the northern Barbados accretionary complex, the Atlantic plate is thrust beneath the Caribbean plate (fig. 6.1) at ~2.8 cm yr⁻¹ [Dixon et al., 1998]. The shallow décollement dips from 180 m below seafloor (mbsf) at the deformation front to 10 km below the seafloor at the back of the accretionary complex, located 125 km arcward [Westbrook et al., 1988]. Results from three Ocean Drilling Program (ODP) Legs, 110, 156, and 171A, and one Deep Sea Drilling Project (DSDP) Leg, 78A, indicate high fluid pressure and provide information about flow rates in the toe of the complex.

      The Barbados complex...

    • 7 Pore Pressure within Underthrust Sediment in Subduction Zones
      (pp. 171-209)
      Demian M. Saffer

      Fluid pressure exerts a fundamental control on a wide range of faulting processes at both subduction zones and in continental settings, including: fault strength [e.g., Rice, 1992; Hubbert and Rubey, 1959], rupture propagation [e.g., Johnson and McEvilly, 1995], strain localization [e.g., Moore and Byrne, 1987], and the taper angle of orogenic wedges [e.g., Hubbert and Rubey, 1959; Davis et al., 1983]. In addition, pore pressure has been postulated to influence the updip limit of seismogenic faulting through its control on effective stress and consolidation state [e.g., Moore and Saffer, 2001; Scholz, 1998]. In this respect, quantifying fluid pressure and its...

    • 8 Deformation and Mechanical Strength of Sediments at the Nankai Subduction Zone: Implications for Prism Evolution and Décollement Initiation and Propagation
      (pp. 210-256)
      Julia K. Morgan, Elizabeth B. Sunderland, E. Blanche Ramsey and Maria V. S. Ask

      Active convergent margins are the locus of some of the largest earthquakes on Earth, a consequence of the combined effects of low-angle fault geometries, cold subducting lithosphere, and the compressional stress environment, that favor large seismic rupture areas of the fault. The extent of the seismically active portions depends on temperature and pressure distributions within the crust and also, the compositional, elastic, and frictional properties of the fault and surrounding rocks [e.g., Scholz, 1990; Tichelaar and Ruff, 1993; Hyndman et al., 1995, 1997; Marone, 1998; Oleskevich et al., 1999]. Earthquake rupture, however, can extend updip along the fault into regions...

    • 9 The Nicaragua Convergent Margin: Seismic Reflection Imaging of the Source of a Tsunami Earthquake
      (pp. 257-287)
      Kirk D. McIntosh, Eli A. Silver, Imtiaz Ahmed, Arnim Berhorst, Cesar R. Ranero, Robyn K. Kelly and Ernst R. Flueh

      The M 7.2 tsunami earthquake of 1992 (fig. 9.1) dramatically increased the interest in Nicaragua margin structure and pointed to its inherent contrasts with neighboring Costa Rica. This earthquake was characterized by long, slow rupture along most of the Nicaragua margin, significant moment release anomalously close to the trench, and generation of a deadly tsunami [Satake, 1994; Velasco et al., 1994; Ihmlé, 1996; Piatanesi et al., 1996]. No similar earthquake/tsunami events are historically known for Costa Rica, and the segmentation of its margin make similar wide-reaching events unlikely [Ambraseys and Adams, 1996; Protti et al., 1995]. With moment release close...

    • 10 How Accretionary Prisms Elucidate Seismogenesis in Subduction Zones
      (pp. 288-315)
      J. Casey Moore, Christie Rowe and Francesca Meneghini

      Accretionary prisms comprise materials that have been transferred from the oceanic plate to the overriding plate in subduction zones. At all but the shallowest levels, near the front of the prism, these sediments and rocks have been underthrust with the lower plate and accreted to the upper plate (fig. 10.1). This accretion process involves a downward migration of the subduction thrust. Thus accretionary prisms constructed by this “underplating” process include faults that were for a period of time subduction thrusts. In addition to the faults active during the initial emplacement of their rocks, accretionary prisms are cut by later faults,...

  7. PART IV Laboratory Studies

    • 11 Friction of the Smectite Clay Montmorillonite: A Review and Interpretation of Data
      (pp. 317-345)
      Diane E. Moore and David A. Lockner

      The smectite clay montmorillonite is an important low-temperature alteration product of mafic igneous volcanic rocks, particularly tuffs and volcanic ash [Grim and Güven, 1978]. Because of the close association of volcanic arcs with subduction zones, montmorillonite can be an important constituent of the accretionary wedges and downgoing sediments in subduction zones (see Table 1 of Vrolijk [1990, and references therein]). According to Vrolijk [1990], airborne volcanic ash incorporated into the hemipelagic deposits of the ocean basins alters to produce weak, smectite-rich horizons, along which the décollement may preferentially form as the oceanic crust is subducted. Localization of the décollement within...

    • 12 Fault Friction and the Upper Transition from Seismic to Aseismic Faulting
      (pp. 346-369)
      Chris Marone and Demian M. Saffer

      Plate boundaries can be divided into three main zones as a function of increasing depth: an aseismic updip zone, the seismogenic zone, and a deep aseismic zone. Identifying the transitions between these zones and the processes controlling their locations are key goals in understanding the mechanics of slip along subduction zone megathrusts. In this paper, we focus on the updip limit of the seismogenic zone and discuss that stability transition in the context of fault-zone frictional rheology.

      Subduction zone megathrusts host a wide range of fault behaviors including interseismic creep, slow earthquakes, earthquakes with normal (fast) rupture velocity, tsunamogenic earthquakes,...

    • 13 Laboratory-Observed Faulting in Intrinsically and Apparently Weak Materials: Strength, Seismic Coupling, Dilatancy, and Pore-Fluid Pressure
      (pp. 370-449)
      N. M. Beeler

      The San Andreas fault between San Juan Batista and Parkfield and sections of the Hayward-Calaveras fault south of San Francisco Bay are of the few well-characterized locations in the world where slip on large displacement throughgoing crustal-scale continental faults is predominately aseismic [Scholz, 1990]. However, in subduction zones, large-scale aseismic slip is very common, and portions of some subduction zones are nearly completely aseismic [Peterson and Seno, 1984]. At the same time, subduction thrust faulting produces the Earth’s largest and most hazardous earthquakes [Kelleher et al., 1974] and the Earth’s largest earthquake-induced tsunamis [Furumoto, 1991]. Understanding the particular conditions that...

  8. PART V Seismic and Geodetic Studies

    • 14 Asperities and Quasi-Static Slips on the Subducting Plate Boundary East of Tohoku, Northeast Japan
      (pp. 451-475)
      Akira Hasegawa, Naoki Uchida, Toshihiro Igarashi, Toru Matsuzawa, Tomomi Okada, Satoshi Miura and Yoko Suwa

      Beneath Tohoku, northeastern Japan, the Pacific plate is subducting downward into the mantle at a convergence rate of ~8 cm/yr [Demets et al., 1994]. It subducts at a very low angle of <10° for its initial descent to a distance ~100 km away from the trench. Then it changes dip angle and descends with a steeper angle of ~30° beneath the land area [Hasegawa et al., 1994; Umino et al., 1995; Hino et al., 1996; Zhao et al., 1997].

      The seismic coupling coefficient is estimated to be ~25% for the plate boundary offshore Sanriku (northern Tohoku) and ~10% for the...

    • 15 Anomalous Earthquake Ruptures at Shallow Depths on Subduction Zone Megathrusts
      (pp. 476-511)
      Thorne Lay and Susan Bilek

      Subduction of oceanic lithosphere occurs along massive interplate thrust faults that are the contact surfaces between overriding and underthrusting plates in convergent margins. These megathrusts accommodate the convergent motions by varying portions of seismic and aseismic slip, with significant variations in geometry and maximum earthquake size from region to region [e.g., Kanamori, 1977; Uyeda and Kanamori, 1979; Ruff and Kanamori, 1980; Pacheco et al., 1993; Scholz and Campos, 1995]. About 90% of the seismic moment released by global earthquakes occurs near subduction zones, with most events involving slip on megathrusts, including the largest recorded events, the 1960 Chile and 1964...

    • 16 Secular, Transient, and Seasonal Crustal Movements in Japan from a Dense GPS Array: Implication for Plate Dynamics in Convergent Boundaries
      (pp. 512-539)
      Kosuke Heki

      Space geodetic techniques such as very long baseline interferometry (VLBI), satellite laser ranging (SLR), Global Positioning System (GPS), and interferometric synthetic aperture radar (InSAR) have been the main tool to study crustal movements for nearly 20 years. The benefits of GPS among such techniques are (1) the relatively inexpensive ground stations (receiver and antenna), (2) a modest amount of raw data, and (3) a dense sampling in time. Point 1 makes GPS suitable for dense deployment of receiving stations in tectonically active regions, while point 2 enables the exchange of data through Internet or public telephone line for rapid data...

    • 17 Elastic and Viscoelastic Models of Crustal Deformation in Subduction Earthquake Cycles
      (pp. 540-575)
      Kelin Wang

      A “subduction earthquake cycle” includes a great earthquake and subsequent strain accumulation that leads to the next event. Here, the use of the word “cycle” by no means implies periodicity: neither the size of the earthquakes nor the duration of the interseismic interval between two events need be a constant. Ideally, a model of earthquake cycles should account for tectonic stress loading of the system, stress relaxation of the rock medium in response to previous earthquakes and ongoing loading, and fault rupture as a frictional instability. Such a comprehensive model is not yet available.

      The loading mechanism is rarely addressed...

    • 18 Distinct Updip Limits to Geodetic Locking and Microseismicity at the Northern Costa Rica Seismogenic Zone: Evidence for Two Mechanical Transitions
      (pp. 576-599)
      Susan Y. Schwartz and Heather R. DeShon

      Subduction is a fundamental geological process generating and modifying continental crust and associated with severe natural hazards (earthquakes, volcanoes, tsunamis). Subduction zones release ~90% of the Earth’s seismic energy [Pacheco et al., 1993] and generate almost all of the world’s great earthquakes. Most of this seismic moment reflects mechanical coupling between the underthrusting and overriding plates along a shallow (<50 km depth) portion of the dipping plate interface termed the seismogenic zone. The earthquake cycle consists of accumulation of elastic strain in the seismogenic zone during the interseismic period and rapid release during an earthquake. Factors affecting coupling and the...

  9. PART VI Regional Scale Deformation

    • 19 Collision Versus Subduction: From a Viewpoint of Slab Dehydration
      (pp. 601-623)
      Tetsuzo Seno

      When a continent or an island arc is impinging on a subduction zone, collision takes place. It is generally believed that buoyancy of the continental or islandarc crust makes subduction difficult [e.g., McKenzie, 1969; Dewey and Bird, 1970; Cloos, 1993] and causes delamination of the upper mantle and/or lower crust of the colliding lithosphere [Bird, 1978; Sacks and Secor, 1990; van den Beukel, 1992] and even stacking of the upper or whole crust [Lyon-Caen and Molnar, 1983; Mattauer, 1986].

      However, there remains a question whether the buoyancy is a unique condition for generating collision. The calculation by van den Beukel...

    • 20 Subduction and Mountain Building in the Central Andes
      (pp. 624-660)
      Jonas Kley and Tim Vietor

      The Andes are the active type example of a subduction-related, or Cordillerantype, mountain belt [Dewey and Bird, 1970]. At a total length of some 7500 km and maximum width of ~700 km, with elevations peaking over 6000 m and maximum crustal thickness exceeding 70 km, the Andes are the world’s second largest mountain belt. At present, no other active continental margin has developed an orogen of similar dimensions. However, also the South American margin, despite a geologic history of more than 200 Myr of continuous subduction, did not begin to grow high topography until ~35 Ma ago, and even then...

  10. List of Contributors
    (pp. 661-664)
  11. Index
    (pp. 665-680)