Seismotectonics & Plate Tectonics
Why study this topic? The challenges
The convergence of tectonic plates often results in the development of faults (and folds) in the Earth’s upper crust, with associated occurrence of large-magnitude (M> 6) earthquakes, over timescales ranging from thousands to millions of years. Because the rate with which large earthquakes rupture individual faults ranges from hundreds to thousands of years, earthquake recurrence is often difficult to constrain by the means of instrumental seismology.
Paleoseismology and the study of active faults extends the time-window of observations for large earthquakes (and faulting) to timescales that include the last ~ 500 thousand years, thereby addressing the growth of faults in space and time due to repeated earthquakes. Paleoseismology addresses questions such as: Are there general rules governing the (often) chaotic earthquake occurrence on faults? What is the impact of fault interactions (and fault intersections) in the recurrence of large-magnitude earthquakes on individual faults? What is the role (and significance) of active faults with no surficial trace? What is the impact of sampling bias on fault parameters (including paleoearthquakes) to the assessment of seismic hazard?
Living in Greece, a country that straddles an active plate-boundary, one of the greatest challenges is to try to understand the mechanism with which large (M>7.5) earthquakes are generated within the subduction plate-interface zone. Having significant indications that the subduction system is a multi-fault system, we strive to better understand (and quantify) the interactions, over different timescales, between faults in the upper-plate with those within the plate-interface zone. Do large-magnitude earthquakes that occur within the plate-interface zone impact on the magnitude and recurrence of earthquakes in the upper-plate (where the most densely populated areas are located)? What is the impact of aseismic deformation on the occurrence of large earthquakes? How is the seismic and aseismic deformation distributed within the plate-interface zone and how these two types combine to accommodate the movement of plates (and large-magnitude earthquakes)? The information resulting from this research will help to better understand the mechanisms of neotectonic (seismic and aseismic) deformation of the Earth’s crust, with ultimate goal the better assessment of the seismic hazard.
Our key research activities
- Growth of faults over geological and earthquake timescales
- Structure and kinematics of normal and strike-slip fault intersections
- Impact of fault interactions on displacement rates and earthquake occurrence
- Impact of sampling biases in paleoseismology
- Geometry, kinematics and seismogenesis within a segmented plate-interface zone
- Structure and kinematics of subduction terminations
- Aseismic slip and large subduction earthquakes
- Interplay between the subduction-thrust and upper-plate faults and its impact on subduction seismogenesis
Methodologies – Research tools
To achieve our goals, we use a wide range of tools and methodologies, from paleoseismological excavations on active faults and study of uplifted paleoshorelines along active subduction margins to the use of geochemical, geophysical and geodetic methods to constrain the age/activity of faults through time. Specifically:
- Palaeoseismological excavations on active faults (field work)
- Fault mapping – Analysis of tectonic geomorphology (field work)
- Cosmogenic isotope and rare earth elements analysis, radiocarbon dating and tephrochronology as tools to identify the timing and size of large past earthquakes
- Analysis of DEM, Lidar and seismic reflection data to identify surface/subsurface faults.
- Elevated paleoshorelines: how marine biota reveals clusters of large earthquakes in the past.
- Mapping the distribution of elastic stresses along active subsidence zones (which parts of the Hellenic system are locally strongly ‘locked’?)
Our operational activities and services
- Hazard Response Team (after large-magnitude onshore earthquakes)
- Contribution to the Seismotectonics committee of Greece (Earthquake Commission in Greece).
- Active Faults Database: NOAFaults (ongoing work).
- Training/supervision of graduate students and post-doctoral researchers.