Recursos de colección

Caltech Authors (130.332 recursos)

Repository of works by Caltech published authors.

Group = Caltech Tectonics Observatory

Mostrando recursos 1 - 20 de 279

  1. Origin and time evolution of subduction polarity reversal from plate kinematics of Southeast Asia

    von Hagke, Christoph; Philippon, Mélody; Avouac, Jean-Philippe; Gurnis, Michael
    We present a regional model of plate geometry and kinematics of Southeast Asia since the Late Cretaceous, embedded in a global plate model. The model involves subduction polarity reversals and sheds new light on the origin of the subduction polarity reversal currently observed in Taiwan. We show that this subduction zone reversal is inherited from subduction of the proto–South China Sea plate and owes its current location to triple junction migration and slab rollback. This analysis sheds new light on the plate tectonic context of the Taiwan orogeny and questions the hypothesis that northern Taiwan can be considered an older,...

  2. Geologic Map of the San Emigdio Mountains, Southern California

    Chapman, Alan D.; Saleeby, Jason B.
    New and existing geologic mapping and geochronology of the San Emigdio Mountains are compiled in a 1:40,000 scale map, establishing the framework for recently published and ongoing studies of Cretaceous assemblages belonging to the Sierra Nevada batholith and the Late Cretaceous San Emigdio Schist. Basement exposures of the San Emigdio Mountains are subdivided into four principal fault-bounded assemblages: (1) mid- to Late Cretaceous shallow-level granitoids and Paleozoic to Mesozoic metamorphic pendant rocks of the Pastoria plate; (2) Early to mid-Cretaceous deep-level intrusives of the Tehachapi-San Emigdio complex; (3) mid-to Late Jurassic gabbro, tonalite, ultramafic rocks, and framework basalts of the Western San Emigdio mafic complex; and (4) the Late...

  3. The Neotethyan Sanandaj-Sirjan zone of Iran as an archetype for passive margin-arc transitions

    Hassanzadeh, Jamshid; Wernicke, Brian P.
    The Sanandaj-Sirjan zone of Iran is a northwest trending orogenic belt immediately north of the Zagros suture, which represents the former position of the Neotethys Ocean. The zone contains the most extensive, best preserved record of key events in the formation and evolution of the Neotethys, from its birth in Late Paleozoic time through its demise during the mid-Tertiary collision of Arabia with Eurasia. The record includes rifting of continental fragments off of the northern margin of Gondwanaland, formation of facing passive continental margins, initiation of subduction along the northern margin, and progressive development of a continental magmatic arc. The...

  4. Climate-change versus landslide origin of fill terraces in a rapidly eroding bedrock landscape: San Gabriel River, California

    Scherler, Dirk; Lamb, Michael P.; Rhodes, Edward J.; Avouac, Jean-Philippe
    Fill terraces along rivers represent the legacy of aggradation periods that are most commonly attributed to climate change. In the North Fork of the San Gabriel River, an arid bedrock landscape in the San Gabriel Mountains, California, a series of prominent fill terraces was previously related to climate-change−induced pulses of hillslope sediment supply that temporarily and repeatedly overwhelmed river transport capacity during the Quaternary. Based on field observations, digital topographic analysis, and dating of Quaternary deposits, we suggest instead that valley aggradation was spatially confined to the North Fork San Gabriel Canyon and was a consequence of the sudden supply...

  5. Seismicity triggered by fluid injection–induced aseismic slip

    Guglielmi, Yves; Cappa, Frédéric; Avouac, Jean-Philippe; Henry, Pierre; Elsworth, Derek
    Anthropogenic fluid injections are known to induce earthquakes. The mechanisms involved are poorly understood, and our ability to assess the seismic hazard associated with geothermal energy or unconventional hydrocarbon production remains limited. We directly measure fault slip and seismicity induced by fluid injection into a natural fault. We observe highly dilatant and slow [~4 micrometers per second (µm/s)] aseismic slip associated with a 20-fold increase of permeability, which transitions to faster slip (~10 µm/s) associated with reduced dilatancy and micro-earthquakes. Most aseismic slip occurs within the fluid-pressurized zone and obeys a rate-strengthening friction law µ = 0.67 + 0.045ln (v/v_0) with v_0 = 0.1 µm/s. Fluid injection primarily...

  6. Numerical modeling of long-term earthquake sequences on the NE Japan megathrust: Comparison with observations and implications for fault friction

    Cubas, Nadaya; Lapusta, Nadia; Avouac, Jean-Philippe; Perfettini, Hugo
    We use numerical modeling to investigate fault properties that explain key features of the 2011 Mw 9.0 Tohoku-Oki earthquake as well as the overall regional behavior of the NE Japan megathrust. In particular, we study the possibility that slip near the trench resulted from thermal pressurization on a shallow patch of the megathrust, and investigate whether low-velocity friction on that patch is rate-strengthening or rate-weakening. Our models also contain a deeper rate-weakening patch, not prone to efficient thermal pressurization, to account for the moderate-sized interplate seismicity. We produce earthquake sequences and aseismic slip in our models using 2D dynamic simulations...

  7. Static Laboratory Earthquake Measurements with the Digital Image Correlation Method

    Rubino, V.; Lapusta, N.; Rosakis, A. J.; Leprince, S.; Avouac, J. P.
    Mapping full-field displacement and strain changes on the Earth’s surface following an earthquake is of paramount importance to enhance our understanding of earthquake mechanics. Currently, aerial and satellite images taken pre- and post-earthquake can be processed with sub-pixel correlation algorithms to infer the co-seismic ground deformations (e.g., [1, 2]). However, the interpretation of this data is not straightforward due to the inherent complexity of natural faults and deformation fields. To gain understanding into rupture mechanics and to help interpret complex rupture features occurring in nature, we develop a laboratory earthquake setup capable of reproducing displacement and strain maps similar to...

  8. Seismic structure in southern Peru: evidence for a smooth contortion between flat and normal subduction of the Nazca Plate

    Dougherty, Sara L.; Clayton, Robert W.
    Rapid changes in slab geometry are typically associated with fragmentation of the subducted plate; however, continuous curvature of the slab is also possible. The transition from flat to normal subduction in southern Peru is one such geometrical change. The morphology of the subducted Nazca Plate along this transition is explored using intraslab earthquakes recorded by temporary regional seismic arrays. Observations of a gradual increase in slab dip coupled with a lack of any gaps or vertical offsets in the intraslab seismicity suggest warping of the slab. Concentrations of focal mechanisms at orientations which are indicative of slab bending are also...

  9. Origin of the modern Chiapanecan Volcanic arc in southern México inferred from thermal models

    Manea, Vlad C.; Manea, Marina
    In southern México, the subducting Cocos slab drastically changes its geometry: from a flat slab in central México to a ∼45° dip angle beneath Chiapas. Also, the currently active volcanic arc, the modern Chiapanecan volcanic arc, is oblique and situated far inland from the Middle America trench, where the slab depth is ∼200 km. In contrast, the Central America volcanic arc is parallel to the Middle America trench, and the slab depth is ∼100 km. A two-dimensional steady-state thermomechanical model explains the calc-alkaline volcanism by high temperature (∼1300 °C) in the mantle wedge just beneath the Central America volcanic arc...

  10. Shallow Rupture of the 2011 Tarlay Earthquake (M_w 6.8), Eastern Myanmar

    Wang, Yu; Lin, Yu-Nung Nina; Simons, Mark; Tun, Soe Thura
    We use L‐band Advanced Land Observation Satellite PALSAR data to infer the distribution of subsurface fault slip during the Tarlay earthquake (M_w 6.8) in eastern Myanmar. We find the total length of surface rupture is approximately 30 km, with nearly 2 m maximum surface offset along the westernmost section of the Nam Ma fault (the Tarlay segment). Finite‐fault inversions constrained by Interferometric Synthetic Aperture Radar (InSAR) and pixel‐tracking data suggest that fault slip is concentrated within the upper 10 km of the crust. Maximum slip exceeds 4 m at a depth between 3 and 5 km. Comparison between field measurements...

  11. A physical model for seismic noise generation by turbulent flow in rivers

    Gimbert, Florent; Tsai, Victor C.; Lamb, Michael P.
    Previous studies suggest that the seismic noise induced by rivers may be used to infer river transport properties, and previous theoretical work showed that bedload sediment flux can be inverted from seismic data. However, the lack of a theoretical framework relating water flow to seismic noise prevents these studies from providing accurate bedload fluxes and quantitative information on flow processes. Here we propose a forward model of seismic noise caused by turbulent flow. In agreement with previous observations, modeled turbulent flow-induced noise operates at lower frequencies than bedload-induced noise. Moreover, the differences in the spectral signatures of turbulent flow-induced and...

  12. Diagnosing Source Geometrical Complexity of Large Earthquakes

    Rivera, L.; Kanamori, H.
    We investigated the possible frequency dependence of the moment tensor of large earthquakes by performing W phase inversions using teleseismic data and equally-spaced narrow, overlapping frequency bands. We investigated frequencies from 0.6 to 3.8 mHz. Our focus was on the variation with frequency of the scalar moment, the amount of non-double-couple, and the focal mechanism. We applied this technique to 30 major events in the period 1994–2013 and used the results to detect source complexity. Based on the results, we classed them into three groups according to the variability of the source parameters with frequency: simple, complex and intermediate. Twelve...

  13. Rupture and variable coupling behavior of the Mentawai segment of the Sunda megathrust during the supercycle culmination of 1797 to 1833

    Philibosian, Belle; Sieh, Kerry; Avouac, Jean-Philippe; Natawidjaja, Danny H.; Chiang, Hong-Wei; Wu, Chung-Che; Perfettini, Hugo; Shen, Chuan-Chou; Daryono, Mudrik R.; Suwargadi, Bambang W.
    We refer to periods of subduction strain accumulation beneath the Mentawai Islands, Sumatra, as “supercycles,” because each culminates in a series of partial ruptures of the megathrust in its final decades. The finale of the previous supercycle comprised two giant earthquakes in 1797 and 1833 and whatever happened in between. This behavior between two great ruptures has implications for how the megathrust will behave between its more recent partial failure, during the M_w 8.4 earthquake of 2007, and subsequent large ruptures. We synthesize previously published coral microatoll records and a large new coral data set to constrain not only these...

  14. Lithological control on the deformation mechanism and the mode of fault slip on the Longitudinal Valley Fault, Taiwan

    Thomas, Marion Y.; Avouac, Jean-Philippe; Gratier, Jean-Pierre; Lee, Jian-Cheng
    The Longitudinal Valley Fault (LVF) in Taiwan is creeping at shallow depth along its southern half, where it is bounded by the Lichi Mélange. By contrast, the northern segment of the LVF is locked where it is bounded by forearc sedimentary and volcanoclastic formations. Structural and petrographic investigations show that the Lichi Mélange most probably formed as a result of internal deformation of the forearc when the continental shelf of South China collided with the Luzon arc as a result of the subduction of the South China Sea beneath the Philippine Sea Plate. The forearc formations constitute the protolith of...

  15. Upper mantle surprises derived from the recent Virginia earthquake waveform data

    Chu, Risheng; Helmberger, Don; Gurnis, Michael
    Recent high resolution regional waveform modeling reveals that the lithosphere beneath the North American craton is subdivided into an upper nearly uniform layer and a lower layer with a high velocity gradient. The boundary occurs at about a depth of 115 km and is responsible for 8° discontinuity in seismic record sections that is often observed in craton environments. Unexpectedly, we find seismic velocities in the lower layer significantly reduced along a corridor from the New Madrid rift zone to Virginia. This reduced velocity in the lower lithosphere may be associated with a possible historic hotspot activity. We also find...

  16. Modeling deformation induced by seasonal variations of continental water in the Himalaya region: Sensitivity to Earth elastic structure

    Chanard, K.; Avouac, J. P.; Ramillien, G.; Genrich, J.
    Strong seasonal variations of horizontal and vertical positions are observed on GPS time series from stations located in Nepal, India, and Tibet (China). We show that this geodetic deformation can be explained by seasonal variations of continental water storage driven by the monsoon. For this purpose, we use satellite data from the Gravity Recovery and Climate Experiment to determine the time evolution of surface loading. We compute the expected geodetic deformation assuming a perfectly elastic Earth model. We consider Green's functions, describing the surface deformation response to a point load, for an elastic homogeneous half-space model and for a layered...

  17. Spatiotemporal evolution of seismic and aseismic slip on the Longitudinal Valley Fault, Taiwan

    Thomas, Marion Y.; Avouac, Jean-Philippe; Champenois, Johann; Lee, Jian-Cheng; Kuo, Long-Chen
    The Longitudinal Valley Fault (LVF) in eastern Taiwan is a high slip rate fault (about 5 cm/yr), which exhibits both seismic and aseismic slip. Deformation of anthropogenic features shows that aseismic creep accounts for a significant fraction of fault slip near the surface, whereas a fraction of the slip is also seismic, since this fault has produced large earthquakes with five M_w>6.8 events in 1951 and 2003. In this study, we analyze a dense set of geodetic and seismological data around the LVF, including campaign mode Global Positioning System(GPS) measurements, time series of daily solutions for continuous GPS stations (cGPS),...

  18. Response of rate-and-state seismogenic faults to harmonic shear-stress perturbations

    Ader, Thomas J.; Lapusta, Nadia; Avouac, Jean-Philippe; Ampuero, Jean-Paul
    Field and laboratory observations show that seismicity has non-trivial period-dependent response to periodic stress perturbations. In Nepal, seismicity shows significant variations in response to annual monsoon-induced stress variations but not to semidiurnal tidal stresses of the same magnitude. Such period dependence cannot be explained by the Coulomb failure model and spring-slider rate-and-state model (SRM). Here, we study seismicity response to periodic stress perturbations in a 2-D continuum model of a rate-and-state fault (that is, a finite rate-and-state fault). We find that the resulting seismicity indeed exhibits nearly periodic variations. Their amplitude is maximum at a certain period, T_a, and decreases...

  19. Zircon age and oxygen isotopic correlations between Bouse Formation tephra and the Lawlor Tuff

    Harvey, Janet C.
    The Bouse Formation in the lower Colorado River trough holds an important record of the onset of the modern drainage patterns in the southwestern United States. It comprises calcareous and clastic infill deposited during flooding of several basins, including the Bristol and Blythe subbasins of Lake Bouse. An intercalated ash bed, which is key to constraining its depositional age, is exposed in two locations, Buzzards Peak and Amboy. Comparative zircon tephrochronology by secondary ion microprobe analysis of U-Pb zircon crystallization ages, U-Th trace element abundances, and oxygen isotopic composition confirm a correlation between the Bouse Formation tephra and the 4.834...

  20. From deep to modern time along the western Sierra Nevada Foothills of California, San Joaquin to Kern River drainages

    Saleeby, Jason; Saleeby, Zorka; Sousa, Frank
    This two day field trip presents an overview of ~ 500 m.y. of diverse geologic history along the southwestern Sierra Nevada Foothills, with focus on several profound geologic features that distinguish this part of the western foothills. These features include (1) a highly deformed oceanic Moho section through the Kings River ophiolite, interpreted as a Carboniferous abyssal core complex; (2) Permo-Carboniferous ophiolitic mélange interpreted to have formed and been emplaced along the SW Cordilleran edge transform, along which the early Mesozoic convergent margin initiated; (3) Early Cretaceous mafic rocks of the western Sierra Nevada batholith, which also characterize much of the Great Valley basement; (4) evidence for 1000-m-scale...

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