TY  - JOUR
A1  - Ballato, Paolo
A1  - Stockli, Daniel F.
A1  - Ghassemi, Mohammad R.
A1  - Landgraf, Angela
A1  - Strecker, Manfred
A1  - Hassanzadeh, Jamshid
A1  - Friedrich, Anke M.
A1  - Tabatabaei, Saeid H.
T1  - Accommodation of transpressional strain in the Arabia-Eurasia collision zone new constraints from (U-Th)/He thermochronology in the Alborz mountains, north Iran
JF  - Tectonics
N2  - The Alborz range of N Iran provides key information on the spatiotemporal evolution and characteristics of the Arabia-Eurasia continental collision zone. The southwestern Alborz range constitutes a transpressional duplex, which accommodates oblique shortening between Central Iran and the South Caspian Basin. The duplex comprises NW-striking frontal ramps that are kinematically linked to inherited E-W-striking, right-stepping lateral to obliquely oriented ramps. New zircon and apatite (U-Th)/He data provide a high-resolution framework to unravel the evolution of collisional tectonics in this region. Our data record two pulses of fast cooling associated with SW-directed thrusting across the frontal ramps at similar to 18-14 and 9.5-7.5 Ma, resulting in the tectonic repetition of a fossil zircon partial retention zone and a cooling pattern with a half U-shaped geometry. Uniform cooling ages of similar to 7-6 Ma along the southernmost E-W striking oblique ramp and across its associated NW-striking frontal ramps suggests that the ramp was reactivated as a master throughgoing, N-dipping thrust. We interpret this major change in fault kinematics and deformation style to be related to a change in the shortening direction from NE to N/NNE. The reduction in the obliquity of thrusting may indicate the termination of strike-slip faulting (and possibly thrusting) across the Iranian Plateau, which could have been triggered by an increase in elevation. Furthermore, we suggest that similar to 7-6-m.y.-old S-directed thrusting predated inception of the westward motion of the South Caspian Basin. Citation: Ballato, P., D. F. Stockli, M. R. Ghassemi, A. Landgraf, M. R. Strecker, J. Hassanzadeh, A. Friedrich, and S. H. Tabatabaei (2012), Accommodation of transpressional strain in the Arabia-Eurasia collision zone: new constraints from (U-Th)/He thermochronology in the Alborz mountains.
Y1  - 2013
U6  - https://doi.org/10.1029/2012TC003159
SN  - 0278-7407
VL  - 32
IS  - 1
SP  - 1
EP  - 18
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Stein, Seth
A1  - Liu, Mian
A1  - Camelbeeck, Thierry
A1  - Merino, Miguel
A1  - Landgraf, Angela
A1  - Hintersberger, Esther
A1  - Kübler, Simon
ED  - Landgraf, Angelika
ED  - Kübler, Simon
ED  - Hintersberger, Esther
ED  - Stein, Seth
T1  - Challenges in assessing seismic hazard in intraplate Europe
JF  - Seismicity, fault rupture and earthquake hazards in slowly deforming regions
N2  - Intraplate seismicity is often characterized by episodic, clustered and migrating earthquakes and extended after-shock sequences. Can these observations - primarily from North America, China and Australia - usefully be applied to seismic hazard assessment for intraplate Europe? Existing assessments are based on instrumental and historical seismicity of the past c. 1000 years, as well as some data for active faults. This time span probably fails to capture typical large-event recurrence intervals of the order of tens of thousands of years. Palaeoseismology helps to lengthen the observation window, but preferentially produces data in regions suspected to be seismically active. Thus the expected maximum magnitudes of future earthquakes are fairly uncertain, possibly underestimated, and earthquakes are likely to occur in unexpected locations. These issues particularly arise in considering the hazards posed by low-probability events to both heavily populated areas and critical facilities. For example, are the variations in seismicity (and thus assumed seismic hazard) along the Rhine Graben a result of short sampling or are they real? In addition to a better assessment of hazards with new data and models, it is important to recognize and communicate uncertainties in hazard estimates. The more users know about how much confidence to place in hazard maps, the more effectively the maps can be used.
Y1  - 2017
SN  - 978-1-86239-745-3
SN  - 978-1-86239-964-8
U6  - https://doi.org/10.1144/SP432.7
SN  - 0305-8719
VL  - 432
SP  - 13
EP  - 28
PB  - The Geological Society
CY  - London
ER  -