Plate Boundary Kinematics Research Articles

Current deformation along the northern Caribbean plate boundary from GNSS measurements in Cuba

Current deformation along the northern Caribbean plate boundary from GNSS measurements in Cuba

Marine Terraces Reveal Complex Near-Shore Upper-Plate Faulting in the Northern Hikurangi Margin, New Zealand

ABSTRACT Recent earthquakes involving multiple fault ruptures highlight the need to evaluate complex coastal deformation mechanisms, which are important for understanding plate boundary kinematics and seismic and tsunami hazards. We compare ages and uplift of the youngest Holocene marine terraces at Puatai Beach and Pakarae River mouth (∼10 km apart) in the northern Hikurangi subduction margin to examine whether uplift is the result of subduction earthquakes or upper-plate fault earthquakes. From stepped platform-cliff morphology, we infer uplift during 2–3 earthquakes and calculate an average uplift-per-event of 2.9±0.5 m at Puatai Beach and 2.0±0.5 m at Pakarae River mouth. Radiocarbon ages from the youngest beach deposit shells on each terrace and a tephra coverbed on one terrace constrain the timing of earthquakes to 1770–1710, 1100–910, and 420–250 cal. B.P. at Puatai Beach, and 1490–1290 and 660–530 cal. B.P. at Pakarae River mouth. The ages differ at each site indicating uplift is neither the result of subduction earthquakes nor single upper-plate fault earthquakes. A reinterpretation of new and existing bathymetry and seismic reflection data, combined with dislocation modeling, indicates that near-shore fault segmentation is more complex than previously thought and ruptures likely involve multiple upper-plate faults. Future updates of the New Zealand National Seismic Hazard Model should revise the northern Hikurangi subduction seismic sources so that rupture does not uplift Puatai Beach and Pakarae River mouth and include new near-shore upper-plate faults as multifault sources.

REGAT: A permanent GPS network in Algeria, configuration and first results

The REGAT (“REseau Géodésique de l'ATlas”) geodetic network is composed of 53 continuously–recording GPS stations distributed in the Algerian Atlas. It spans the whole width of the Algerian coast and reaches 300 km inland, with inter-sites distance of about 100 km. One additional site is located in Tamanrasset in the southernmost part of the country. The network, whose oldest stations started operating in 2007, encompasses the main active tectonic features of the most seismically active segment of the Nubia-Eurasia plate boundary in the Western Mediterranean. Here we describe the network configuration, the data collection and analysis strategy, as well as some preliminary results on horizontal GPS velocities. A detailed analysis of the velocity field in terms of plate boundary kinematics is the topic of a separate publication. The REGAT network fills an important gap in our knowledge of present-day plate boundary deformation in the Western Mediterranean. It will soon be enhanced by an additional 100 sites in order to improve deformation monitoring with a higher spatial resolution for a better assessment of the regional seismic hazard.

Chapter 18 Tectonic and volcanic deformation at São Miguel Island, Azores, observed by continuous GPS analysis 2008–13

Abstract We use a Global Positioning System (GPS) to unravel the complex geodynamics of the Azores Triple Junction where tectonic and volcanic activities coexist. The temporal analysis of densely distributed continuous GPS data on São Miguel for the period 2008–13 provides an improved understanding of interactions between present-day plate boundary kinematics and volcanic deformation. We find a high-strain-rate (0.28 ppm a –1 ) zone between Congro and Furnas, which accommodates about 50% of the Eurasian–Nubian plate spreading as predicted by the MORVEL plate angular velocity model. The seismic unrest of Fogo–Congro (2011–12) shows a strong similarity with the Matsushiro (Japan) earthquake swarm (1965–66) and the Campi Flegrei (Italy) volcanic unrest (1969–72 and 1982–85), in that an edifice-scale inflation associated with intense high-frequency earthquakes and inflation–deflation reversals coincided with a sharp drop in seismicity. We propose the following hypothesis for the Fogo unrest: (1) the primary inflation source beneath Fogo promotes lateral diffusion of fluids that is selectively guided by existing cracks/fissures formed from regional extension; (2) an influx of fluids increases pressure in cracks/fissures and generates lower-frequency earthquakes; and (3) discharge of fluids causes pressure decrease and dilatancy recovery (i.e. seismic quiescence).

Low-temperature thermochronology of the Black and Panamint mountains, Death Valley, California: Implications for geodynamic controls on Cenozoic intraplate strain

We use apatite and zircon (U-Th)/He thermochronometry to evaluate space-time patterns and tectonic drivers of Miocene to Pliocene deformation within the Death Valley area, eastern California. Zircon He ages from the footwall of the Amargosa–Black Mountains detachment in the Black Mountains record continuous cooling and exhumation from 9 to 3 Ma. Thermal modeling of data from the central Black Mountains suggests that this cooling took place during two intervals: a period of rapid footwall exhumation from 10 to 6 Ma, followed by slower (<5 mm/yr) exhumation since 6 Ma. Cumulative exhumation is estimated to be 10–16 km. Paleodepth reconstruction of cooling ages from the footwall of the Panamint-Emigrant detachment, in the central Panamint Range, also show two periods of cooling. Zircons record late Miocene cooling, whereas apatite He ages show punctuated exhumation at ca. 4 Ma. The results suggest the Panamint Range experienced a minimum of 7.2 km of exhumation since ca. 12 Ma. The new data, when evaluated within the context of published fault timing data, suggest that the transition from Basin and Range extension to dextral transtension is spatially and temporally distinct, beginning at ca. 11–8 Ma in ranges to the east and north of the Black Mountains and migrating westward into eastern Death Valley at 6 Ma. Initiation of dextral transtension was coincident with a major change in plate-boundary relative motion vectors. Data from Panamint Range and several ranges to the west of Death Valley indicate transtension initiated over a large area at ca. 3–4 Ma, coeval with proposed lithospheric delamination in the central and southern Sierra Nevada Range. Our results suggest that the transition from extension to dextral transtension may reflect an evolution in tectonic drivers, from plate-boundary kinematics to intraplate lithospheric delamination.

Relationship between outer forearc subsidence and plate boundary kinematics along the Northeast Japan convergent margin

Tectonic erosion along convergent plate boundaries, whereby removal of upper plate material along the subduction zone interface drives kilometer‐scale outer forearc subsidence, has been purported to explain the evolution of nearly half the world's subduction margins, including part of the history of northeast Japan. Here, we evaluate the role of plate boundary dynamics in driving forearc subsidence in northeastern Japan. A synthesis of newly updated analyses of outer forearc subsidence, the timing and kinematics of upper plate deformation, and the history of plate convergence along the Japan trench demonstrate that the onset of rapid fore‐arc tectonic subsidence is contemporaneous with upper plate extension during the opening of the Sea of Japan and with an acceleration in convergence rate at the trench. In Plio‐Quaternary time, relative uplift of the outer forearc is contemporaneous with contraction across the arc and a decrease in plate convergence rate. The coincidence of these changes across the forearc, arc, backarc system appears to require an explanation at the scale of the entire plate boundary. Similar observations along other western Pacific margins suggest that correlations between forearc subsidence and major changes in plate kinematics are the rule, rather than the exception. We suggest that a significant component of forearc subsidence at the northeast Japan margin is not the consequence of basal tectonic erosion, but instead reflects dynamic changes in plate boundary geometry driven by temporal variations in plate kinematics. If correct, this model requires a reconsideration of the mass balance and crustal recycling of continental crust at nonaccretionary margins.

Changes in plate boundary kinematics: Punctuated or smoothly varying — Evidence from the mid-Cenozoic transition from lithospheric extension to shortening in New Zealand

Abstract The marine magnetic anomaly record and plate kinematics derived from that data provide evidence of numerous cases of significant changes in plate motions and plate interactions. However, in most cases the temporal resolution provided by the marine record does not discriminate between punctuated (abrupt) or smooth variations in plate motions. During a 10 million year period (~ 30 Ma to 20 Ma), the Euler poles (stage poles) describing Australia–Pacific relative plate motion migrated more than 20° in latitude. The New Zealand segment of the plate boundary is close to the location of the Euler poles and their migration making the tectonics of its plate boundary structures particularly sensitive to the history of plate kinematics. Based on the rapid southward migration of the Euler (stage) poles from north of New Zealand to south of the landmass, there is an expected rapid, migrating transition from an extensional (stage pole north of the site) to transpressional (stage pole south of the site) plate boundary system. The geologic signature of this rapid change in plate boundary kinematics is preserved in the stratigraphic record of a suite of basin deposits that span the latitudinal sweep of the migrating Euler poles. Analyses of these deposits indicate that the timing of the transition from extensional to transpressional tectonics shows a continuous and systematic southward sweep, indicating that the changes in Australia–Pacific plate motions during the 30 Ma–20 Ma interval were smoothly continuous and not punctuated.

Relationship between outer forearc subsidence and plate boundary kinematics along the Northeast Japan convergent margin

Relationship between outer forearc subsidence and plate boundary kinematics along the Northeast Japan convergent margin

Tsunami Hazard Posed to New Zealand by the Kermadec and Southern New Hebrides Subduction Margins: An Assessment Based on Plate Boundary Kinematics, Interseismic Coupling, and Historical Seismicity

We assess the tsunami hazard posed to New Zealand by the Kermadec and southern New Hebrides subduction margins. Neither of these subduction zones has produced tsunami large enough to cause significant damage in New Zealand over the past 150 years of well-recorded history. However, as this time frame is short compared to the recurrence interval for major tsunamigenic earthquakes on many of the Earth’s subduction zones, it should not be assumed that what has been observed so far is representative of the long term. For each of these two subduction zones we present plate kinematic and fault-locking results from block modelling of earthquake slip vector data and GPS velocities. The results are used to estimate the current rates of strain accumulation on the plate interfaces where large tsunamigenic earthquakes typically occur. We also review data on the larger historical earthquakes that have occurred on these margins, as well as the Global CMT catalogue of events since 1976. Using this information we have developed a set of scenarios for large earthquakes which have been used as initial conditions for the COMCOT tsunami code to estimate the subsequent tsunami propagation in the southwest Pacific, and from these the potential impact on New Zealand has been evaluated. Our results demonstrate that there is a significant threat posed to the Northland and Coromandel regions of New Zealand should a large earthquake (Mw ≳8.5) occur on the southern or middle regions of the Kermadec Trench, and that a similarly large earthquake on the southern New Hebrides Trench has the potential to strongly impact on the far northern parts of New Zealand close to the southern end of the submarine Three Kings Ridge. We propose logic trees for the magnitude–frequency parameters of large earthquakes originating on each trench, which are intended to form the basis for future probabilistic studies.

Revised slip rates for the Alpine fault at Inchbonnie: Implications for plate boundary kinematics of South Island, New Zealand

The northeast-striking, dextral-reverse Alpine fault transitions into the Marlborough Fault System near Inchbonnie in the central South Island, New Zealand. New slip-rate estimates for the Alpine fault are presented following a reassessment of the geomorphology and age of displaced late Holocene alluvial surfaces of the Taramakau River at Inchbonnie. Progressive avulsion and abandonment of the Taramakau floodplain, aided by fault movements during the late Holocene, have preserved a left-stepping fault scarp that grows in height to the northeast. Surveyed dextral (22.5 ± 2 m) and vertical (4.8 ± 0.5 m) displacements across a left stepover in the fault across an alluvial surface are combined with a precise maximum age from a remnant tree stump (≥1590–1730 yr) to yield dextral, vertical, and reverse-slip rates of 13.6 ± 1.8, 2.9 ± 0.4, and 3.4 ± 0.6 mm/yr, respectively. These values are larger (dextral) and smaller (dip slip) than previous estimates for this site, but they reflect advances in the local chronology of surfaces and represent improved time-averaged results over 1.7 k.y. A geological kinematic circuit constructed for the central South Island demonstrates that (1) 69%–89% of the Australian-Pacific plate motion is accommodated by the major faults (Alpine-Hope-Kakapo) in this transitional area, (2) the 50% drop in slip rate on the Alpine fault between Hokitika and Inchbonnie is taken up by the Hope and Kakapo faults at the southwestern edge of the Marlborough Fault System, and (3) the new slip rates are more compatible with contemporary models of strain partitioning presented from geodesy.

A New Look at Evidence for a Wadati-Benioff Zone and Active Convergence at the North Panama Deformed Belt

The nature of the northern boundary of the Panama microplate, often referred to as the north Panama deformed belt (NPDB), has been the subject of much speculation. Previous studies have used a variety of data, including teleseismic, gravity, bathymetric, marine magnetic, and field studies of uplift and tsunami deposits, as well as modified Mercalli intensity distributions from historic earthquakes to reveal the nature of the NPDB. Data have been collected for over 30 yrs and yet the character of the NPDB remains unclear. Current analyses and interpretation provide a number of mutually exclusive options and much controversy. In this article we examine local and regional seismicity combined with teleseismic observations and historic earthquake data to present an alternative analysis for the NPDB. Using small earthquakes recorded by a local network we image a well-defined Wadati–Benioff zone dipping southward beneath the Panama microplate. These data provide new evidence regarding the nature of Panama microplate–Caribbean plate boundary kinematics and demonstrate the existence of an active subduction zone. A more complete understanding of the nature of the seismicity and plate interactions along the NPDB offshore Panama, including a subduction zone capable of producing earthquakes of M >7, should be included in future earthquake hazard assessments.

Metamorphism, transient mid‐crustal rheology, strain localization and the exhumation of high‐grade metamorphic rocks

We present a series of three‐dimensional numerical models investigating the effects of metamorphic strengthening and weakening on the geodynamic evolution of convergent orogens that are constrained by observations from an exposed mid‐crustal section in the New England Appalachians. The natural mid‐crustal section records evidence for spatially and temporally variable mid‐crustal strength as a function of metamorphic grade during prograde polymetamorphism. Our models address changes in strain rate partitioning and topographic uplift as a function of strengthening/weakening in the middle crust, as well as the resultant changes in deformation kinematics and potential exhumation patterns of high‐grade metamorphic rock. Results suggest that strengthening leads to strain rate partitioning around the zone and suppressed topographic uplift rates whereas weakening leads to strain rate partitioning into the zone and enhanced topographic uplift rates. Deformation kinematics recorded in the orogen are also affected by strengthening/weakening, with complete reversals in shear sense occurring as a function of strengthening/weakening without changes in plate boundary kinematics.

Late Cenozoic tectonism, collapse caldera and plateau formation in the central Andes

Abstract The evolution of Andean volcanism including the formation of late Miocene to Recent collapse calderas on the Puna plateau is generally interpreted in terms of the kinematic framework of the Nazca and South American Plates. We present evidence that caldera dynamics and associated ignimbrite volcanism are genetically linked to the activity of first-order NW–SE-striking zones of left-lateral transtension on the local and regional scales. Consequently, ages of collapse calderas indicate activity of these fault zones which initiated at about 10 Ma on the Puna plateau. The onset of such faulting points to a change in the deformation regime from dominantly vertical thickening to orogen-parallel stretching upon reaching maximum crustal thickness and critical surface elevation. Horizontal magma sheets that formed at mid-crustal level possibly due to heat advection by volume increase of asthenospheric mantle below thickened crust were tapped by sub-vertical faults. This accounts well for the observed tectono-magmatic phenomena at surface. It follows that formation of collapse calderas and eruption of voluminous ignimbrites appear to be related to the mechanical evolution of the Andean plateau rather than to changes in the geometry of the Wadati–Benioff zone or plate boundary kinematics.

Progressive arcward contraction of a Mesozoic-Tertiary fore-arc basin, southwestern Sacramento Valley, California

The modern Sacramento Valley intermontane basin is the successor to a deformed Mesozoic-Tertiary fore-arc basin. Based on analysis of seismic reflection profiles, drill hole data, and surface mapping, we propose a model for progressive arcward contraction of the fore-arc basin in the Rumsey Hills region, southwestern Sacramento Valley, beginning in Cretaceous and continuing episodically through Cenozoic time. We present our interpretation in the form of a kinematically restorable forward model. The major tectonic and depositional events include (1) mid-Cretaceous or older shortening of fore-arc basin strata along imbricate, west-dipping thrust faults; (2) erosion of the deformed fore-arc strata; (3) onlap of Cenomanian and younger fore-arc strata onto deformed older strata and crystalline Sierran basement; (4) renewed shortening in latest Cretaceous to early Tertiary, accommodated by delamination of Upper Cretaceous strata from the mid-Cretaceous angular unconformity, tectonic wedging, and west-directed backthrusting; (5) erosion of the deformed Upper Cretaceous strata and deposition of the Eocene Capay Formation; (6) uplift and east-directed shortening from Eocene to late Neogene, with local erosion of the Capay Formation over the ancestral Rumsey Hills; (7) uplift of the northern Coast Ranges beginning ca. 3.4 Ma, and deposition of the Pliocene-Pleistocene Tehama Formation in the western Sacramento Valley as a syntectonic molasse; and (8) fault-propagation folding of the Tehama Formation beginning ca. 0.5–1.0 Ma. With the exception of Quaternary shortening, progressive arcward contraction of the western basin margin occurred during east-dipping subduction and plate convergence beneath western California. The deformation of the ancestral Sacramento Valley fore-arc basin is analogous to arcward contraction of the Tobago Trough in the Lesser Antilles arc-trench system, and suggests that tectonic wedging may be a relatively common process in the evolution of fore-arc regions. Late Quaternary shortening has occurred in a transpressional setting and suggests a continuity in structural style despite a change in plate boundary kinematics from convergence to transpression during the past 3–5 m.y.

Plate-boundary kinematics in the Alps: Motion in the Arosa suture zone

The Arosa zone forms a melange complex along the Penninic/Austroalpine boundary and belongs to the main Alpine suture zone. Accretion and plate collision occurred during Cretaceous and lower Tertiary time. A mixture of ophiolitic rocks and pelagic sediments is imbricated with flysch and blocks of Austroalpine (continental) derivation. We present a description of deformation structures, an analysis of strain, and a kinematic interpretation based on structural work. Deformation histories of imbricates show a translation path that was west-directed between ca. 110 and 50 Ma and north-directed thereafter. The kinematics of the Arosa zone agrees with the recently deduced displacement history of the Austroalpine units in the Eastern Alps during the Cretaceous orogeny. This calls for a predominantly top-to-the-west imbrication of Austroalpine and Penninic units and is in contradiction to what is inferred in most models of the Eastern Alps. A direct relation between the deformation along the Austroalpine margin and relative plate motion existed.