Distribution of Interseismic Coupling Along the North and East Anatolian Faults Inferred From InSAR and GPS Data

<p>The North Anatolian Fault (NAF) has produced numerous major earthquakes. After decades of quiescence, the M<span>w </span>6.8 Elazı˘g earthquake (24 January 2020) has recently reminded us that the East Anatolian Fault (EAF) is also capable of producing significant earthquakes. To better estimate the seismic hazard associated with these two faults, we jointly invert interferometric synthetic aperture radar (InSAR) and GPS data to image the spatial distribution of interseismic coupling along the eastern part of both the NAF and EAF.We perform the inversion in a Bayesian framework, enabling to estimate uncertainties on both long-term relative plate motion and coupling. We find that coupling is high and deep (0–20 km) on the NAF and heterogeneous and superficial (0–5 km) on the EAF. Our model predicts that the Elazı˘g earthquake released between 200 and 250 years of accumulated moment, suggesting a bicentennial recurrence time.</p>

Fault evolution and strain partitioning within deforming continents

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Diffuse deformation within continents and over broad plate boundary zones deviates from the prediction of plate tectonics theory. Some of the deforming continents are now well delineated by space geodetic measurements, but the cause of such diffuse deformation remains poorly understood. My Ph.D. research focuses on two regions: 1) Fault evolution and Strain partitioning in Southern California: High-precision GPS measurements have enabled kinematic modeling of the present-day strain partitioning between these faults, but the causes of such strain partitioning and fault evolution remain uncertain. Using a three-dimensional viscoelasto-plastic finite element model, I have explored how the plate boundary fault system evolves to accommodate the relative plate motion in Southern California. My results show that, when the plate boundary faults are not optimally orientated to accommodate the relative plate motion, new faults will be initiated. In particular, the Big Bend of the San Andreas Fault, which is the main plate boundary fault, impedes the relative plate motion, thus forces the development of a system of secondary faults. 2) Active strain rates of crustal deformation in mainland China: In the past decades Chinese scientists and international teams have measured GPS velocities at more than a thousand sites in mainland China, allowing calculation of detailed spatial distribution of the crustal strain rates. Using the latest GPS data, I have calculated strain rates in different tectonic provinces in China and compared them with neotectonic data. I have also calculated strain rates using earthquakes and geological fault slip rates. The differences of strain rates derived from different data sets show the time-scale dependence of strain rates. Comparing GPS strain rates with seismic moment release patterns illustrates the limitations of using earthquake catalog for earthquake hazard analysis.

5. Rigid plates of lithosphere

‘Rigid plates of lithosphere’ explains that because of the lithosphere’s strength, essentially rigid plates of lithosphere move with respect to one another across the surface of the Earth. Their rigidity allows their rates of relative motion and of their total displacements to be described by rotations about axes passing through the centre of the Earth, or poles of rotation. Global Positioning System (GPS) measurements corroborate the inferences drawn both from rates of seafloor spreading determined using magnetic anomalies and from directions of relative plate motion determined using orientations of transform faults and fault plane solutions of earthquakes along plate boundaries.

Kinematic analysis of deformed structures in a tectonic mélange: a key unit for the manifestation of transpression along the Zagros Suture Zone, Iran

Kinematic analysis of mélange fabrics provides critical information concerning tectonic processes and evaluation of the kinematics of ancient relative plate motion. Systematic kinematic analysis of deformed structures within a tectonic mélange exposed along the Zagros Suture Zone elucidates that this zone is an ancient transpressional boundary. The mélange is composed of a greywacke and mudstone matrix surrounding various lenses, blocks and ribbons of radiolarian chert, limestone, sandstone, pillow lava, tuff, serpentinite, shale and marl. The deformation fabrics of the mélange suggest that the mélange units were tectonically accreted at shallow levels within a subduction complex, resulting in layer-parallel extension and shearing along a NW–SE-trending suture that juxtaposes the Afro-Arabian continent to the south and the Central Iranian microcontinents to the north. The tectonic mélange is characterized by subhorizontal layer-parallel extension and subsequent heterogeneous non-coaxial shear resulting in alternating asymmetric and layer-parallel extensional fabrics such as P–Y fabrics and boudinaged layers. Kinematic data suggest that the mélange formed during oblique subduction of the Neo-Tethys oceanic lithosphere in Late Cretaceous time. Kinematic shear sense indicators reveal that the slip direction (N9°E to N14°E) during accretion-related deformations reflects the relative plate motion between the Afro-Arabian continent and Central Iranian microcontinents during Late Cretaceous to Miocene times.

The 4 December 19487 earthquake (Mw 604): Evidence of reverse faulting Beneath the Tres Marías escarpment and its implications for the Rivera-North American relative plate motion

El temblor del 4 de diciembre de 1948 es el sismo más grande que ha sido registrado en el segmento norte del límite de placas Rivera-Norteamérica. Este evento ocasionó muertes y daños importantes en el penal de las Islas Marías. En este trabajo se recopilaron sismogramas de estaciones regionales y telesísmicas con el fin de determinar su mecanismo focal. El mecanismo resultante muestra una falla inversa de alto ángulo con los ejes P orientados NE-SW. El mecanismo obtenido coincide con las soluciones de dos temblores más pequeños localizados a lo largo del Escarpe de las Tres Marías. La magnitud estimada para el evento de 1948 es de Mw6.4. Este valor está basado en la amplitud de las ondas superficiales registradas en la estación De Bilt (Holanda). La dirección de deslizamiento del mecanismo resultante puede interpretarse como el reflejo del movimiento relativo entre las placas de Rivera y Norteamérica. De esta manera la placa de Rivera parece estar cabalgando por debajo del Escarpe de Tres Marías en dirección NE-SW. El mecanismo obtenido contribuye a la estimación del movimiento relativo entre ambas placas en una región donde existen pocos datos al respecto.