Oblique subduction
Oblique subduction is a form of
Obliquity in plate convergence causes differences in
Moreover, collision of two plates leads to
Deformation features
Forearc slivers
Forearc slivers are partly detached continental blocks of the overriding plates.
Moreover, some forearc slivers occur in the absence of well defined strike-slip fault systems, and sliver motions are not purely strike-slip.[15]
Trench parallel strike-slip fault systems
Trench parallel
Fault | Subducting plate | Overriding plate | Strike slip motion | Motion rate |
---|---|---|---|---|
Philippine Fault | Philippine Sea Plate | Sunda Plate | Left-lateral motion | 20–25 mm per year[16] |
Japan Median Tectonic Line | Philippine Sea Plate | Eurasian Plate | Right-lateral motion | 5 mm per year[17] |
Liquiñe-Ofqui Fault | Nazca Plate | South American Plate | Right-lateral motion | 6.8–28 mm per year[18] |
Orientation of strike slip faults
Vertical
Hypothetical models | Figures | Description |
---|---|---|
Vertical fault model | During oblique subduction, the convergence and coupling between two plates create horizontal strike slip fault is thought to be vertical from earth surface down to the subducting plate.[10]
| |
Mega-splay fault system model |
In Nankai Trough (Formed by oblique subduction of the Philippine Sea Plate),[22] seismic profiles reveal that the margin parallel strike slip fault and thrust structures are linked by the mega splay fault system, which align in a parallel manner with the subducting plate (i.e. Philippine Sea Plate).[21] | |
Curved fault model | The strike-slip fault in Andes. Based on analysis on shear stress distribution,[19] Ormeño et al., (2017) suggested that it is a curving strike slip fault.[19] The hypothetical geometry coincides with an curving reflector obtained in the seismic reflection profile of the subduction zone.[23]
|
Slip accommodating mechanisms
Trench parallel slip component from oblique subduction may not be fully accommodated by the aforementioned trench parallel
Margin parallel strike-slip faults in subducting plates
Ishii et al., (2013) suggested that the trench parallel
In the Sumatra subduction zone, the trench parallel slip component is measured to be approximately 45 mm per year, the motion rate of northern Great Sumatra Fault ranges from 1 to 9 mm per year with the maximum rate of 13 mm per year.[24][25] The result shows that the trench parallel slip component of at least 32 mm per year is left.[24]
On 11 April 2012, a Mw 8.6 earthquake occurred in the subducting plate (i.e. the Indo-Australian Plate). Strike-slip seismicity was recorded in the earthquake.[24] This infers strike slip fault systems are present in the descending slab and they may potentially accommodate slip component from oblique subduction.[24]
Location of faults | Features |
---|---|
Upper plate |
|
Subducting plate |
|
Strain partitioning
Short-term deformation: Localized shear zone
Short-term deformation is mainly
The orientation of tectonic force gradually rotates toward the trench normal direction. This attributes to the decline of trench parallel component when the force leaves the plate coupling zone.[27][32][34] In this way, only the frontal part, rather than the whole upper plate, is dragged by the subducting slab.[27]
Long-term deformation: Formation of forearc sliver and strike slip fault
Long-term deformation occurs at geological time scale.[30] Under continuous oblique subduction, the aforementioned frontal part of the upper plate permanently accommodates the trench parallel component.[27][34] In this way, the orientation of tectonic force rotates gradually toward the trench parallel direction.[27]
Strong and continuing tectonic force in trench parallel direction leads to the development of trench parallel
The 1771 Great Yaeyama Tsunami
The tsunami occurred in the southwestern part of the
Subduction velocity | 50 to 63 mm per year[35] |
Subduction direction | N60°W to N50°W[36] |
Subduction obliquity angle | 40° to 60°[37] |
Tectonic setting
In the plate boundary, an approximately 80 km long and 30 km wide depression is observed.
Oblique subduction and tsunami
Block rotation
Oblique subduction has led to rotation of microblocks about nearby poles of rotation (See also:
Examples of oblique subduction-induced block rotation are identified in North Island, Cascadia and New Guinea.[39]
Example: North Island oblique subduction zone
Tectonic setting
The North Island oblique subduction zone in New Zealand was established by the obliquely subducting Pacific Plate beneath the Indo-Australian Plate.[12] A trench parallel strike slip fault system, North Island Dextral Fault Belt, was formed.[12] Based on geological and geodetic data, five tectonic blocks are identified in the region.[12] These blocks are separated by block-bounding faults.[12]
Microblock rotation
Based on GPS measurement, a clockwise rotation of microblocks at a rate of 0.5° to 3.8° per million year relative to the
In addition, the block rotation accommodates 25% to 65% of the trench parallel component from oblique subduction.
Rotation mechanism
In the oblique subduction zone, the sinking slab is characterized by the Hikurangi plateau in the south.[12] The thickness of this oceanic plateau ranges from 15 km to 10 km along the oceanic trench.[12] The along strike thickness variation leads to differential subduction rate.[12] In the southern trench, thick oceanic plateau induces high collisional resistance forces that cripples the subduction process.[12] However, the thin oceanic crust in the north is subducted. This activated the tectonic block rotations about a nearby axis.[12]
Closure of Northeastern Paleo-Tethys Ocean
Geological setting
The Qinling-Dabieshan orogen in central China consists of three separate plates, including the north China plate, the Qinling-Dabieshan microplate, and the south China plate.[13] Geological and geochemical analysis suggest that there was an ocean basin between the plates and it was part of the Paleo-Tethys Ocean[40]
Evidence of oblique subduction
Tectonic features of oblique subduction, for example a right lateral strike-slip thrust belt are identified in the tectonic zone.[40] These evidence suggest that the south China plate was obliquely subducted to the northwest beneath the north China plate in the Early Mesozoic and led to the closure of the northeastern Paleo-Tethys Ocean.[40]
Example of oblique subduction
Peru-Chile trench
The Peru–Chile Trench is part of the Andean oblique subduction zone that was formed as a result of oblique subduction between the sinking Nazca Plate and the South American Plate.[27] The current subduction direction is at east-north-east (see the summary below).[41] However, geological record shows southeast subduction direction in Late Cretaceous period.[42]
Subduction velocity | 66 mm per year[43] |
Subduction direction | N78°E[41] |
Subduction obliquity angle | Range from 22° to 32°[44] |
Margin parallel strike slip faults
Four major trench parallel
The
The Atacama Fault and the Precordilleran Fault are located in northern Chile. The Atacama Fault extends more than 1,000 km.[50] It was formed during the Mid to Late Jurassic period as a left-lateral fault due to oblique subduction of the Phoenix Plate.[51] The fault system has been inactive since the Miocene Period. The right lateral slip rate is estimated to be less than 1 mm per year since the Pliocene.[52]
The Precordilleran Fault, also known as the Domeyko fault, is composed of several anastomosing faults (i.e. branching and irregular faults) including Sierra Moreno Fault, West Fault and Limon Verde.[53] Precordilleran Fault was formed in the Late Eocene.[54] In Neogene period, the fault system changed from left lateral to right lateral motion along with the uplift of the Precordillera.[55][56][57]
Forearc sliver
Two major forearc slivers are observed along the Peru-Chile Trench.[59][60][58] The Peruvian Sliver, also known as Inca Sliver, has a width of 300 to 400 km and a total length of over 1,500 km.[59] It extends from the Gulf of Guayaquil in the north to the Altiplano in the south.[60] The continental boundary is located between the Western Cordillera and the Eastern Cordillera.[60]
Chiloe Microplate, also known as Chiloe Block, is a forearc sliver that detached along the
See also
References
- ^ ISBN 978-0-12-369396-9, retrieved 2021-11-11
- S2CID 242138731.
- ^ ISSN 0012-821X.
- ISSN 0091-7613.
- ^ .
- ^ S2CID 128791885.
- ^ ISSN 0012-821X.
- .
- PMID 32766442.
- ^ hdl:2060/19720023718.
- ^ PMID 30206405.
- ^ ISSN 2156-2202.
- ^ .
- ^ S2CID 129732044.
- .
- ISSN 0091-7613.
- S2CID 55416525.
- PMID 33782456.
- ^ ISSN 0718-7106.
- ^ S2CID 54801874.
- ^ S2CID 46140064.
- ISSN 1525-2027.
- S2CID 127545947.
- ^ ISSN 0091-7613.
- .
- .
- ^ ISBN 978-3-540-24329-8, retrieved 2021-09-20
- .
- ISSN 0148-0227.
- ^ S2CID 133168588.
- ISSN 0096-3941.
- ^ S2CID 128643365.
- .
- ^ ISBN 978-1-118-67044-6, retrieved 2021-09-20
- .
- S2CID 15306498.
- S2CID 39123076.
- ^ ISSN 1525-2027.
- ^ ISSN 1944-8007.
- ^ .
- ^ .
- .
- .
- .
- ISSN 0040-1951.
- ISSN 0040-1951.
- ^ Rosenau M (2004) Tectonis of the Southern Andean intra-arc zone (38°–42°S), PhD thesis, Freie Universität Berlin
- ^ Hervé, F. (1977) Petrology of the Crystalline Basement of the Nahuelbuta Mountains, South-Central Chile. In: Ishikawa, T. and Aguirre, L., Eds., Comparative Studies on the Geology of the Circum—Pacific Orogenic Belt in Japan and Chile, Japanese Society for the Promotion of Science, London, 1-52.
- ^ ISSN 0091-7613.
- .
- S2CID 129227152.
- .
- ISSN 0361-0128.
- S2CID 129215864.
- ISSN 0040-1951.
- ^ Tomlinson AJ, Blanco N (1997b) Structural evolution and displacement history of the West Fault system, Precordillera, Chile: part II, postmineral history. In: VIII Congresso Geológico Chileno, ACTAS Vol III – Nuevos Antecedentes de la Geologí a del Distrio de Chuquicamata, Periodo 1994–1995, Sessión 1: Geología Regional, Universidad Catolica del Norte, pp 1878–1882
- ^ Dilles J, Tomlinson AJ, Martin M, Blanco N (1997) The El Abra and Fortuna complexes: a porphyry copper batholith sinistrally displaced by the Falla Oeste. In: VIII Congresso Geológico Chileno, ACTAS Vol III – Nuevos Antecedentes de la Geologí a del Distrio de Chuquicamata, Periodo 1994–1995, Sessión 1: Geología Regional: pp 1878–1882, Universidad Catolica del Norte, Chile
- ^ .
- ^ ISSN 1752-0894.
- ^ S2CID 132735222.