Present-day crustal deformation and geodetic strain in the vicinity of Dholavira - Harappan civilization site, Kachchh, western part of the Indian plate

Contributions from the detrital approach to unravelling the timing of India-Asia collision and Himalayan evolution

10.5194/egusphere-egu21-1916 ◽

2021 ◽

Author(s):

Yani Najman ◽

Shihu Li

Keyword(s):

Subduction Zone ◽

Crustal Deformation ◽

Earth Science ◽

Island Arc ◽

Current Understanding ◽

Indian Plate ◽

Geophysical Research

Knowledge of the timing of India-Asia collision and associated Tethyan closure in the region is critical to advancement of models of crustal deformation.&#160;&#160; One of a number of methods traditionally used to constrain the time of India-Asia collision is the detrital approach. This involves determination of when Asian material first arrived on the Indian plate, with most recent estimates documenting collision at ca 60 Ma (e.g. Hu et al, Earth Science Reviews 2016). However, more recently, such data and a number of other approaches providing data previously used to determine the timing of India-Asia collision, have been controversially re-interpreted to represent collision of India with an Island arc, with terminal India-Asia collision occurring significantly later, ca 34 Ma (e.g. Aitchison et al, J. Geophysical Research 2007). Clearly, for the detrital approach to advance the debate, discrimination between Asian detritus and arc detritus is required. Such a discrimination was proposed in Najman et al (EPSL 2017), dating the timing of terminal India-Asia collision at 54 Ma. However, this evidence is far from universally accepted.&#160; For example, such data are at variance with various palaeomagnetic studies which suggest that an oceanic Transtethyan subduction zone existed 600-2300 kms south of the Eurasian margin in the Paleocene &#160;(e.g. Martin et al, PNAS 2020) and therefore these authors propose different explanations to explain the detrital data.&#160; This presentation will discuss the uncertainties associated with our current understanding of the timing of India-Asia collision.

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Velocity field and crustal deformation of broader Athens plain (Greece) from a dense geodetic network

Journal of Applied Geodesy ◽

10.1515/jag-2019-0012 ◽

2019 ◽

Vol 13 (4) ◽

pp. 305-316 ◽

Cited By ~ 1

Author(s):

M. Foumelis

Keyword(s):

Velocity Field ◽

Crustal Deformation ◽

Strain Tensor ◽

Geodetic Network ◽

Motion Field ◽

Strain Accumulation ◽

Tectonic Structures ◽

Single Strain ◽

Geodetic Strain ◽

Tectonic Boundary

Abstract The broader area of Athens, a region exhibiting relatively low crustal deformation, was stroke in 1999 by a catastrophic earthquake posing serious questions regarding strain accumulation in slow deforming regions located within active geodynamic regimes. In the present study, the establishment of a dense geodetic network, primarily designed to monitor local tectonic movements is reported. A comprehensive GNSS velocity field, over the period 2005–2008, as well as calculated geodetic strain rates is presented. It is shown that a single strain tensor is insufficient to express the heterogeneity of the local geodetic field. Local variability of strain is successfully depicted, indicating the western part of Athens as the area of higher strain accumulation. Maximum dilatation rates occur along a NNE-SSW direction between Parnitha Mt. and Thriasio basin. The observed dilatation can be associated to WNW-ESE trending active fault zones, which appear to abruptly terminate towards East along a major NNE-SSW Miocene tectonic boundary. These findings are consistent to the stress field responsible for the Athens 1999 earthquake, also in agreement with geological and tectonic observations. Finally, the implications of the observed motion field on the understanding of the kinematics and dynamics of the region as well as the role of inherited inactive tectonic structures are discussed.

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The Horizontal Kinematics of the North Island of New Zealand

10.26686/wgtn.16959568.v1 ◽

2021 ◽

Author(s):

◽

Bryan Arthur Sissons

Keyword(s):

Indian Plate ◽

Taupo Volcanic Zone ◽

Plate Boundaries ◽

Advantages And Disadvantages ◽

Spreading Axis ◽

The North ◽

Central Plate ◽

Back Arc ◽

Geodetic Strain ◽

Shear Belt

The advantages and disadvantages of the 'displacement' approach and the 'strain' approach to the analysis of repeated geodetic surveys for crustal deformation are discussed and two methods of geodetic strain analysis are described in detail. Repeated geodetic surveys in the central North Island show i) secular widening of the Taupo Volcanic Zone (TVZ) at 7 mm y-1 without significant transcurrent motion ii) north-south dextral motion at 14 mm y-1 and east-west narrowing at 4 mm y-1 across the northern end of the North Island Shear Belt iii) 3.1 m extension at 135' across a 15 km-wide region north of Lake Taupo, and adjacent zones of compressive rebound all associated with the 1922 Taupo Earthquakes. From the epicentral distribution and horizontal strain pattern a 15 km-square fault dipping 40' and striking parallel to the TVZ is inferred for the 1922 earthquakes. The seismic moment, 1.3 x 10 26 dyne cm, and the stress drop, 134 bars, are abnormally high for the TVZ. Widening of the TVZ is considered to be back-arc spreading. The spreading axis is postulated to extend northeast into the Havre Trough via a north-south dextral transform; and southwest into the Waverley Fault Zone and Waimea Depression via the sinistral reverse Raetihi Transform. Deformation of the North Island is not homogeneous. Fault zones are idealized as line plate boundaries and four plates -Indian, Central, Kermadec and Pacific - are postulated to account for the deformation. The Indian-Pacific macroplate pole is adopted and non-unique positions and rotation rates for the remaining poles are determined from geodetic strain data and the geometry of plate interactions. The Central Plate is moving away from the Indian Plate at the back-arc spreading axis; the Kermadec Plate is moving dextrally with respect to the Central Plate at the North Island Shear Belt which accommodates most of the transcurrent component of motion between the Indian and Pacific plates in the North Island and gives almost pure subduction of the Pacific Plate under the Kermadec Plate at the Hikurangi Margin.

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The Horizontal Kinematics of the North Island of New Zealand

10.26686/wgtn.16959568 ◽

2021 ◽

Author(s):

◽

Bryan Arthur Sissons

Keyword(s):

Indian Plate ◽

Taupo Volcanic Zone ◽

Plate Boundaries ◽

Advantages And Disadvantages ◽

Spreading Axis ◽

The North ◽

Central Plate ◽

Back Arc ◽

Geodetic Strain ◽

Shear Belt

The advantages and disadvantages of the 'displacement' approach and the 'strain' approach to the analysis of repeated geodetic surveys for crustal deformation are discussed and two methods of geodetic strain analysis are described in detail. Repeated geodetic surveys in the central North Island show i) secular widening of the Taupo Volcanic Zone (TVZ) at 7 mm y-1 without significant transcurrent motion ii) north-south dextral motion at 14 mm y-1 and east-west narrowing at 4 mm y-1 across the northern end of the North Island Shear Belt iii) 3.1 m extension at 135' across a 15 km-wide region north of Lake Taupo, and adjacent zones of compressive rebound all associated with the 1922 Taupo Earthquakes. From the epicentral distribution and horizontal strain pattern a 15 km-square fault dipping 40' and striking parallel to the TVZ is inferred for the 1922 earthquakes. The seismic moment, 1.3 x 10 26 dyne cm, and the stress drop, 134 bars, are abnormally high for the TVZ. Widening of the TVZ is considered to be back-arc spreading. The spreading axis is postulated to extend northeast into the Havre Trough via a north-south dextral transform; and southwest into the Waverley Fault Zone and Waimea Depression via the sinistral reverse Raetihi Transform. Deformation of the North Island is not homogeneous. Fault zones are idealized as line plate boundaries and four plates -Indian, Central, Kermadec and Pacific - are postulated to account for the deformation. The Indian-Pacific macroplate pole is adopted and non-unique positions and rotation rates for the remaining poles are determined from geodetic strain data and the geometry of plate interactions. The Central Plate is moving away from the Indian Plate at the back-arc spreading axis; the Kermadec Plate is moving dextrally with respect to the Central Plate at the North Island Shear Belt which accommodates most of the transcurrent component of motion between the Indian and Pacific plates in the North Island and gives almost pure subduction of the Pacific Plate under the Kermadec Plate at the Hikurangi Margin.

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Lithospheric Deformation and Active Tectonics of the NW Himalayas, Hindukush, and Tibet

Lithosphere ◽

10.2113/2021/7866954 ◽

2021 ◽

Vol 2021 (1) ◽

Author(s):

Ishtiaq A. K. Jadoon ◽

Lin Ding ◽

Saif-ur-Rehman K. Jadoon ◽

Zahid I. Bhatti ◽

Syed T. H. Shah ◽

...

Keyword(s):

Crustal Deformation ◽

Gravity Data ◽

Active Tectonics ◽

Ductile Deformation ◽

Indian Plate ◽

The Tibetan Plateau ◽

Mantle Lithosphere ◽

Lithospheric Deformation ◽

Himalayan Mountain ◽

Mountain Belts

Abstract The Himalayan Mountain System (HMS) and the Tibetan Plateau (TP) represent an active mountain belt, with continent-continent collision. Geological and geophysical (seismological modeling, seismic reflection, and gravity) data is reviewed herein for an overview of the lithospheric deformation and active tectonics of this orogen. Shallow crustal deformation with dominance of thrusting along the margins of the TP is interpreted with normal faulting in the center and strike-slip deformation with the lateral translation of blocks, over a wedge of ductile deformation. The seismicity is the linear concentration over the margins of the orogen to ~20 km depth with exception of the Hindukush and Pamir having seismicity to 300 km depth with an interpretation of sinking Indian and Asian lithospheres. The lithospheric structure is represented by mechanically weak surfaces representing décollement to 15 km depth over the basement, low-velocity zone (LVZ) at ~20 km, the Moho at ~40-82 km, and the lithosphere-asthenosphere boundary (LAB) at 130-200 km depth. The décollement, termed as the Himalayan Mountain Thrust (HMT), is inferred to be rooted at the base of the Moho in central Tibet. Along this fault, brittle crustal deformation is interpreted to ~15-20 km depth, with brittle-ductile deformation along LVZ and ductile slip with crustal duplexing along the lower crust. The mantle lithosphere of the Indian plate is inferred as duplicated with the wedging of the Asian mantle lithosphere. The active tectonics of the TP is proposed to follow the mechanics of thrusting, similar to the foreland deformation of the mountain belts and accretionary prisms.

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Crustal movement and strain distribution in East Asia revealed by GPS observations

Scientific Reports ◽

10.1038/s41598-019-53306-y ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 1

Author(s):

Ming Hao ◽

Yuhang Li ◽

Wenquan Zhuang

Keyword(s):

East Asia ◽

Crustal Deformation ◽

North China ◽

Mainland China ◽

Pacific Plate ◽

Indian Plate ◽

Stress Axis ◽

The Pacific ◽

Ryukyu Arc ◽

Gps Observations

AbstractEast Asia is bounded by the Indian plate to the southwest and the Pacific and Philippine plates to the east, and has undergone complex tectonic evolution since ~55 Ma. In this study, we collect and process three sources of GPS datasets, including GPS observations, GPS positioning time series, and published GPS velocities, to derive unified velocity and strain rate fields for East Asia. We observed southward movement and arc-parallel extension along the Ryukyu Arc and propose that the maximum principal stress axis (striking NEE) in North China could be mainly induced by westward subduction of the Pacific plate and the southward movement of the Ryukyu Arc. The large EW-trending sinistral shear zone that bounds North China has been created by eastward movement of South China to the south and westward subduction of the Pacific plate to the north. GPS velocity profiles and strain rates also demonstrate that crustal deformation in mainland China is controlled by northeastward collision of the Indian plate into Eurasia and westward subduction of the Pacific and Philippine Sea plates beneath Eurasia. In particular, the India-Eurasia continental collision has the most extensive impact, which can reach as far as the southern Lake Baikal. The viscous behavior of the subducting Pacific slab also drives interseismic deformation of North China. The crustal deformation caused by Philippine oceanic subduction is small and is limited to the region between the southeast coast of mainland China and Taiwan island. However, the principal compressional strain around eastern Taiwan is the largest in the region.

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