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Geomorphological and sedimentological signals of deformation in a silent subduction zone: An investigation of the Makran (Iran)

Applicant Simpson Guy
Number 155904
Funding scheme Project funding (Div. I-III)
Research institution Section des Sciences de la Terre et de l'environnement Université de Genève
Institution of higher education University of Geneva - GE
Main discipline Geology
Start/End 01.01.2015 - 31.12.2018
Approved amount 296'293.00
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Keywords (5)

sedimentology; geomorphology; isotope dating; tectonics; earthquakes

Lay Summary (French)

Lead
Les séismes les plus importants et dévastateurs ont lieu, pour la plupart, dans des régions ou une plaque subducte sous une autre, comme le long des côtes Japonaises ou en Amérique du Sud. Dans ces régions, les séismes de grande magnitude ont souvent une récurrence de plusieurs centaines d’années, ce qui rend leur étude en se basant sur l’enregistrement historique difficile. Même si la plupart des séismes ont lieu en quelques minutes et sont la cause de violentes secousses, un nouveau type de séisme, impliquant un glissement graduel sur une période allant de semaines à plusieurs mois, a été découvert récemment (communément nommés ‘séismes lents’ ) . Ces séismes relâchent d’énormes quantités d’énergie (similaires à leurs homologues rapides), mais ne produisent pas de secousses destructives. Cette découverte met en évidence des lacunes fondamentales dans notre compréhension du développement de la déformation le long des marges actives.
Lay summary
Cette étude se focalise sur le Makran, une zone de subduction au SE de l’Iran. Dans cette région, aucun séisme de grande amplitude n’a été enregistré dans les temps historiques. Nous souhaiterions comprendre si ceci est dû à un glissement lent de la région, ou si un séisme destructeur de grande envergure est à prévoir. Pour aborder ce problème, nous allons entreprendre du travail de terrain dans cette région isolée pour étudier et dater des plages, terrasses et sédiments récemment soulevés. Nos investigations devraient nous permettre de placer de nouvelles contraintes sur la vitesse et la cyclicité de ces évènements sismiques. Ces résultats pourraient aussi nous aider à mieux comprendre le développement de la déformation dans d’autres marges actives majeures sur Terre.
Direct link to Lay Summary Last update: 06.11.2014

Lay Summary (English)

Lead
Most of the worlds’ largest and most destructive earthquakes occur in regions where one plate subducts beneath the other, such as along the coasts of Japan and South America. In these regions, the large earthquakes are often separated by several hundred years, making them difficult to study on the basis of historical records. Although most earthquakes occur in a matter of minutes and are linked with strong shaking, recently a new type of earthquake has been discovered that involve gradual slip over a period of weeks to months (so called ‘slow earthquakes’). These earthquake release large amounts of energy (similar to their more rapid counterparts), but produce no destructive shaking. This discovery highlights fundamental gaps in our knowledge regarding how deformation is accommodated along active plate boundaries.
Lay summary
This project focused on the remote Makran subduction zone of SE Iran. This region has never experienced a large earthquake in historical times. We would like to understand if this is because the region slips in slow events, or rather that that a large destructive earthquake is imminent. To study this problem, we will carry out field work in this remote region to study and date recently uplifted marine beaches, terraces and sediments. Our investigation should enable us to place new constraints on how often rapid slip take place in this region and how rapidly they occur. These results should also help us to better understand how deformation is accommodated along other major plate boundaries on earth.

 

 

Direct link to Lay Summary Last update: 06.11.2014

Responsible applicant and co-applicants

Employees

Name Institute

Publications

Publication
What do earthquakes reveal about ambient shear stresses in the upper crust?
Simpson Guy (2018), What do earthquakes reveal about ambient shear stresses in the upper crust?, in Geology, 46(8), 703-706.
Practical Finite Element Modeling in Earth Science using Matlab
SimpsonGuy (2017), Practical Finite Element Modeling in Earth Science using Matlab, Wiley, Cambridge.
Accumulation of permanent deformation during earthquake cycles on reverse faults
Simpson Guy (2015), Accumulation of permanent deformation during earthquake cycles on reverse faults, in Journal of Geophysical Research: Solid Earth, 120(3), 1958-1974.

Collaboration

Group / person Country
Types of collaboration
Abbas Bahroudi, University of Tehran Iran (Asia)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Elias Samankassou, University of Geneva, Department of Earth Science Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Sebastien Castelltort, University of Geneva, Department of Earth Science Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Massimo Chiaradia, University of Geneva Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Andeas Eisenhauer, GEOMAR Kiel Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Pascal Kindler, University of Geneva Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
T Vinnemann, University of Lausanne Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Associated projects

Number Title Start Funding scheme
134990 TECTONO-STRATIGRAPHIC INVESTIGATION OF THE NEOGENE ZAGROS FORELAND BASIN (IRAN) 01.06.2011 Project funding (Div. I-III)
101695 Interactions between deformation and sediment routing systems in active fold-and-thrust belts: an investigation in the Marche Apennines (Italy) 01.12.2003 Project funding (Div. I-III)

Abstract

The Makran subduction zone along the southern coast of Iran has not experienced a great earthquake during recent historical times (It is possible that the Makran region was hit by a large earthquake in 1483 though the size and location of this event are highly disputed (see Musson (2009) for discussion)). This can be interpreted as evidence that convergence on this plate boundary is accommodated aseismically, or that it experiences large magnitude earthquakes with recurrence times longer than the historical record. Evidence concerning which of these hypotheses is most correct is currently inconclusive. The Makran coastline is long known to display spectacular signs of recent tectonic unrest including raised beaches and flights of uplifted marine terraces that are both warped and faulted. However, what these features reveal about the nature of short term deformation is currently hindered by poor age control and lack of detailed study that is both systematic and regional. In order to resolve these issues, and to better understand the nature of plate boundary deformation at the temporal scale of typical seismic cycles (100's -1000's of years), we propose a detailed investigation in the coastal region of the Makran subduction zone in Iran. We plan to undertake a multidisciplinary approach focusing on three main geological archives. First, we will investigate a series of raised beach strandlines that potentially record up to 20 recent coseismic uplift events. Age constraints will be obtained by radiocarbon dating of marine shells. Second, we will undertake a detailed study of the deformed and uplifted marine terraces, correlating the surfaces along the coast and dating the sequence using a combination of U-Th, Sr and O isotopes. Third, we will study Late Quaternary recently exposed shallow marine sediments which display evidence for repeated, abrupt changes in palaeoenvironment and water depth. Age constraints will be carried out by performing U-Th or Sr dating on shell material. This new data will enable us to constrain changes in relative sea level, and hopefully eventually to disentangle pulsed versus continuous tectonic vertical motions from effects related to Quaternary eustatic sea level variation.In this proposal we request funding for one PhD student for a duration of 3 years. This student would be based in the Department of Earth Science at the University of Geneva and would be supervised by Dr Guy Simpson, a permanent faculty member within this department. The requested funds include a standard salary, costs for two field seasons in the Makran for the student and supervisor, laboratory costs to perform dating and funds to cover travel and participation to conferences for the student and supervisor. The project involves collaboration with Dr Bahroudi at the University of Tehran (Iran) who will assist us scientifically in the field and with logistical support. This project will also take advantage of several internal collaborators notably S\'ebastien Castelltort for sedimentology and geomorphology, Elias Samankassou for isotope stratigraphy and Pascal Kindler for Quaternary sea level change. The project could also involve collaborations with Anton Eisenhauer (GEOMAR Kiel) for U-Th dating, Torsten Vinnemann (University of Lausanne) for O isotope analysis and Massimo Chiaradia (University of Geneva) for Sr isotope analysis.
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