New views on earthquake faulting in the Zagros fold-and-thrust belt of Iran

Nissen, Edwin; Tatar, M.; Jackson, James; Allen, Mark B.

doi:10.1111/j.1365-246x.2011.05119.x

Cited by 191 publications

(318 citation statements)

References 87 publications

(207 reference statements)

Supporting

Mentioning

297

Contrasting

Order By: Relevance

“…The Turkish-Iranian Plateau is a region of intense volcanic activity [Pearce et al, 1990], and the long-wavelength positive free-air gravity anomaly in the region [Lemoine, 1996] suggests this activity may be related to mantle circulation. The high geothermal gradients associated with the volcanism therefore imply that earthquakes are only likely to occur down to depths of less than 10-15 km, as observed in most other mountain ranges [Molnar and Lyon-Caen, 1989;Nissen et al, 2011]. One possibility for the deep extent of slip in the 2011 Van event lies within the portion of the Arabian Plate that was underthrust beneath the southern margin of the Turkish-Iranian Plateau before shortening jumped north to the Greater Caucasus at 5 Ma [Avdeev and Niemi, 2011].…”

Section: Tectonics Of the Turkish-iranian Plateaumentioning

confidence: 99%

The 2011 Mw 7.1 Van (Eastern Turkey) earthquake

Elliott

Copley

Holley³

et al. 2013

JGR Solid Earth

100

View full text Add to dashboard Cite

[1] We use interferometric synthetic aperture radar (InSAR), body wave seismology, satellite imagery, and field observations to constrain the fault parameters of the M w 7.1 2011 Van (Eastern Turkey) reverse-slip earthquake, in the Turkish-Iranian plateau. Distributed slip models from elastic dislocation modeling of the InSAR surface displacements from ENVISAT and COSMO-SkyMed interferograms indicate up to 9 m of reverse and oblique slip on a pair of en echelon NW 40°-54°dipping fault planes which have surface extensions projecting to just 10 km north of the city of Van. The slip remained buried and is relatively deep, with a centroid depth of 14 km, and the rupture reaching only within 8-9 km of the surface, consistent with the lack of significant ground rupture. The up-dip extension of this modeled WSW striking fault plane coincides with field observations of weak ground deformation seen on the western of the two fault segments and has a dip consistent with that seen at the surface in fault gouge exposed in Quaternary sediments. No significant coseismic slip is found in the upper 8 km of the crust above the main slip patches, except for a small region on the eastern segment potentially resulting from the M w 5.9 aftershock on the same day. We perform extensive resolution tests on the data to confirm the robustness of the observed slip deficit in the shallow crust. We resolve a steep gradient in displacement at the point where the planes of the two fault segments ends are inferred to abut at depth, possibly exerting some structural control on rupture extent.

show abstract

Section: Tectonics Of the Turkish-iranian Plateaumentioning

confidence: 99%

The 2011 Mw 7.1 Van (Eastern Turkey) earthquake

Elliott

Copley

Holley³

et al. 2013

JGR Solid Earth

100

View full text Add to dashboard Cite

show abstract

“…Nissen et al (2014) disputed this view based upon the range of earthquake depths compatible with seismic waveforms. However, it is clear that the depth distribution of faulting within the Zagros Nissen et al (2011) and this study. Black mechanisms were obtained by previous body-waveform modelling studies and are labelled with the depth in kilometres.…”

Section: Introductionmentioning

confidence: 99%

“…Where thrust events have one very low-angle nodal plane, and one near-vertical plane, it has been assumed that the fault plane has a shallow dip. Black arrows show results from body waveform modelling (from the catalogue of Nissen et al (2011) and this study), grey from well-constrained CMT solutions (with a percentage double-couple greater than 80 per cent, as defined by Jackson et al (2002)), and white arrows show a first-motion result where the polarity observations tightly bracket the nodal plane geometry (Jackson & M c Kenzie 1984). Slip vectors from aftershocks are not included due to the likelihood of the fault motion direction being affected by stress changes from the associated mainshock in addition to the large-scale tectonic forces.…”

Section: Slip Vector Azimuth and Large-scale Tectonicsmentioning

confidence: 99%

“…This procedure is commonly used, and thorough descriptions can be found in Nabelek (1984) and Taymaz et al (1991). We use a velocity model for these seismic inversions, and for the geodetic inversions described below, which was obtained by a microseismicity study in the Masjed-Soleyman region of the Zagros Mountains, 50-100 km to the SE of the Murmuri earthquake sequence (Nissen et al 2011). This model has P-wave velocities of 5.0 km s −1 in the top 10 km, 5.95 km s −1 at depths of 10-14 km, and then 6.15 km s −1 for the remainder of the crust.…”

Section: B O Dy-wav E F O R M M O D E L L I N Gmentioning

confidence: 99%

“…Nissen et al (2011) suggested that seismic slip is mostly concentrated in the lower part of the 10-15 km thick sedimentary sequence, known as the 'Competent Group', composed of a sequence more than 5 km thick dominated by Mesozoic and Paleozoic platform carbonates. This group is underlain by the Precambrian-Cambrian Hormoz salt in the Fars arc of the southeastern Zagros ( Fig.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Seismogenic faulting of the sedimentary sequence and laterally variable material properties in the Zagros Mountains (Iran) revealed by the August 2014 Murmuri (E. Dehloran) earthquake sequence

Copley¹,

Karasözen

Oveisi

et al. 2015

Geophys. J. Int.

Self Cite

View full text Add to dashboard Cite

S U M M A R YWe present source models for the August 2014 Murmuri (Dehloran) earthquake sequence in the Zagros Mountains of Iran. An M w 6.2 mainshock was followed by an aftershock sequence containing five events of M w ≥ 5.4. Models of P and SH waveforms show that all events had dominantly thrust-faulting mechanisms, and had centroid depths that place them within the thick sedimentary sequence, above the crystalline basement. The combination of our estimated focal mechanisms, relative relocations of the event hypocentres and the surface displacement patterns observed using InSAR imply that the mainshock and largest aftershock ruptured different fault planes and both contributed to the surface deformation. The fault planes both slipped in horizontally elongated patches, possibly due to rheological layering limiting the updip and downdip extent of rupture. The slip vector of the Murmuri mainshock implies that the decollement beneath the Lorestan Arc is weaker than any such feature beneath the Dezful Embayment, providing an explanation for the plan-view sinuosity of the range-front of the Zagros Mountains.

show abstract

Zagros “phantom earthquakes” reassessed—The interplay of seismicity and deep salt flow in the Simply Folded Belt?

et al. 2014

Self Cite

View full text Add to dashboard Cite

Unraveling the contributions of main shock slip, aftershocks, aseismic afterslip, and postseismic relaxation to the deformation observed in earthquake sequences heightens our understanding of crustal rheology, triggering phenomena, and seismic hazard. Here, we revisit two recent earthquakes in the Zagros mountains (Iran) which exhibited unusual and contentious aftereffects. The M w ∼6 earthquakes at Qeshm (2005) and Fin (2006) are both associated with large interferometric synthetic aperture radar (InSAR) signals, consistent with slip on steep reverse faults in carbonate rocks of the middle sedimentary cover, but small aftershocks detected with local seismic networks were concentrated at significantly greater depths. This discrepancy can be interpreted in one of two ways: either (1) there is a genuine vertical separation between main shock and aftershocks, reflecting a complex stress state near the basement-cover interface, or (2) the aftershocks delimit the main shock slip and the InSAR signals were caused by shallow, updip afterslip (phantom earthquakes) with very similar magnitudes, mechanisms, and geographical positions as the original earthquakes. Here, we show that main shock centroid depths obtained from body waveform modeling-which in this instance is the only method that can reveal for certain the depth at which seismic slip was centered-strongly support the first interpretation. At Qeshm, microseismic aftershock depths are centered at the level of the Hormuz Formation, an Infracambrian sequence of intercalated evaporitic and nonevaporitic sediments. These aftershocks may reflect the breaking up of harder Hormuz sediments and adjacent strata as the salt flows in response to main shock strain at the base of the cover. This work bolsters recent suggestions that most large earthquakes in the Zagros are contained within carbonate rocks in the midlower sedimentary cover and that the crystalline basement shortens mostly aseismically.

show abstract

New views on earthquake faulting in the Zagros fold-and-thrust belt of Iran

Cited by 191 publications

References 87 publications

The 2011 Mw 7.1 Van (Eastern Turkey) earthquake

The 2011 Mw 7.1 Van (Eastern Turkey) earthquake

Seismogenic faulting of the sedimentary sequence and laterally variable material properties in the Zagros Mountains (Iran) revealed by the August 2014 Murmuri (E. Dehloran) earthquake sequence

Zagros “phantom earthquakes” reassessed—The interplay of seismicity and deep salt flow in the Simply Folded Belt?

Contact Info

Product

Resources

About