Chaman Fault
Encyclopedia
The Chaman Fault is a major, active geological fault in Pakistan and Afghanistan
that runs for over 850 km. Tectonically
, it is actually a system of related geologic faults that separates the Eurasian Plate
from the Indo-Australian Plate
. It is a terrestrial, primarily transform
, left-lateral strike-slip fault. The slippage rate along the Chaman fault system as the Indo-Australian Plate moves northward (relative to the Eurasian Plate) has been estimated at 10 mm/yr or more. In addition to its primary transform aspect, the Chaman fault system has a compressional component
as the Indian Plate is colliding with the Eurasian Plate. This type of plate boundary is sometimes called a transpressional boundary.
From the south, the Chaman fault starts at the triple junction
where the Arabian Plate
, the Eurasian Plate
and the Indo-Australian Plate
meet, which is just off the Makran Coast
of Pakistan. The fault tracks northeast across Balochistan
and then north-northeast into Afghanistan, runs just to the west of Kabul
, and then northeastward across the right-lateral-slip Herat fault, up to where it merges with the Pamir fault system north of the 38º parallel. The Ghazaband and Ornach-Nal faults are often included as part of the Chaman fault system. South of the triple junction, where the fault zone lies undersea and extends southwest to approximately 10ºN 57ºE, it is known as the Owen Fracture Zone
.
While there is general agreement that the fault is slipping at a rate of at least 10 mm/yr, there is a report of volcanic rocks in Pakistan dated to 2 m.y. BP which have been offset such as to indicate a slip rate of 25–35 mm/yr. Offsets have been described throughout the fault in Pakistan that are young enough that “only the alluvium of the bottom of active dry washes is not displaced.”
The parallel mountain ranges of eastern Balochistan, (east to west) the Kirthar Mountains
, the Khude Mountains, the Zarro Mountains, the Pab Mountains and the Mor Mountains, are a result of the compressional plate boundary and are aligned parallel to the Chaman fault movement. The fault itself is west of these ranges.
Afghanistan
Afghanistan , officially the Islamic Republic of Afghanistan, is a landlocked country located in the centre of Asia, forming South Asia, Central Asia and the Middle East. With a population of about 29 million, it has an area of , making it the 42nd most populous and 41st largest nation in the world...
that runs for over 850 km. Tectonically
Plate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...
, it is actually a system of related geologic faults that separates the Eurasian Plate
Eurasian Plate
The Eurasian Plate is a tectonic plate which includes most of the continent of Eurasia , with the notable exceptions of the Indian subcontinent, the Arabian subcontinent, and the area east of the Chersky Range in East Siberia...
from the Indo-Australian Plate
Indo-Australian Plate
The Indo-Australian Plate is a major tectonic plate that includes the continent of Australia and surrounding ocean, and extends northwest to include the Indian subcontinent and adjacent waters...
. It is a terrestrial, primarily transform
Transform fault
A transform fault or transform boundary, also known as conservative plate boundary since these faults neither create nor destroy lithosphere, is a type of fault whose relative motion is predominantly horizontal in either sinistral or dextral direction. Furthermore, transform faults end abruptly...
, left-lateral strike-slip fault. The slippage rate along the Chaman fault system as the Indo-Australian Plate moves northward (relative to the Eurasian Plate) has been estimated at 10 mm/yr or more. In addition to its primary transform aspect, the Chaman fault system has a compressional component
Convergent boundary
In plate tectonics, a convergent boundary, also known as a destructive plate boundary , is an actively deforming region where two tectonic plates or fragments of lithosphere move toward one another and collide...
as the Indian Plate is colliding with the Eurasian Plate. This type of plate boundary is sometimes called a transpressional boundary.
From the south, the Chaman fault starts at the triple junction
Triple junction
A triple junction is the point where the boundaries of three tectonic plates meet. At the triple junction a boundary will be one of 3 types - a ridge, trench or transform fault - and triple junctions can be described according to the types of plate margin that meet at them...
where the Arabian Plate
Arabian Plate
The Arabian Plate is one of three tectonic plates which have been moving northward over millions of years and colliding with the Eurasian Plate...
, the Eurasian Plate
Eurasian Plate
The Eurasian Plate is a tectonic plate which includes most of the continent of Eurasia , with the notable exceptions of the Indian subcontinent, the Arabian subcontinent, and the area east of the Chersky Range in East Siberia...
and the Indo-Australian Plate
Indo-Australian Plate
The Indo-Australian Plate is a major tectonic plate that includes the continent of Australia and surrounding ocean, and extends northwest to include the Indian subcontinent and adjacent waters...
meet, which is just off the Makran Coast
Makran
The present day Makran is a semi-desert coastal strip in the south of Sindh, Balochistan, in Iran and Pakistan, along the coast of the Arabian Sea and the Gulf of Oman. The present day Makran derived its name from Maka, a satrap of Achaemenid Empire....
of Pakistan. The fault tracks northeast across Balochistan
Balochistan (Pakistan)
Balochistan is one of the four provinces or federating units of Pakistan. With an area of 134,051 mi2 or , it is the largest province of Pakistan, constituting approximately 44% of the total land mass of Pakistan. According to the 1998 population census, Balochistan had a population of...
and then north-northeast into Afghanistan, runs just to the west of Kabul
Kabul
Kabul , spelt Caubul in some classic literatures, is the capital and largest city of Afghanistan. It is also the capital of the Kabul Province, located in the eastern section of Afghanistan...
, and then northeastward across the right-lateral-slip Herat fault, up to where it merges with the Pamir fault system north of the 38º parallel. The Ghazaband and Ornach-Nal faults are often included as part of the Chaman fault system. South of the triple junction, where the fault zone lies undersea and extends southwest to approximately 10ºN 57ºE, it is known as the Owen Fracture Zone
Owen Fracture Zone
The Owen Fracture Zone is a transform fault which runs along the eastern boundary of the Arabian Plate, separating it from the Indo-Australian Plate for most of its length, and from the African Plate for a much shorter distance...
.
While there is general agreement that the fault is slipping at a rate of at least 10 mm/yr, there is a report of volcanic rocks in Pakistan dated to 2 m.y. BP which have been offset such as to indicate a slip rate of 25–35 mm/yr. Offsets have been described throughout the fault in Pakistan that are young enough that “only the alluvium of the bottom of active dry washes is not displaced.”
The parallel mountain ranges of eastern Balochistan, (east to west) the Kirthar Mountains
Kirthar Mountains
Kirthar Mountains are a Mountain Range located in Balochistan and Sindh provinces of Pakistan. The Range extends southward for about 190 miles from the Mula River in east-central Balochistan to Cape Monze west of Karachi on the Arabian Sea.Kirthar National Park is one of the largest wildlife...
, the Khude Mountains, the Zarro Mountains, the Pab Mountains and the Mor Mountains, are a result of the compressional plate boundary and are aligned parallel to the Chaman fault movement. The fault itself is west of these ranges.
Significant earthquakes along the fault
- 1505, 5 July or 6th – An earthquake created a 60 km long surface rupture along a transverse fault in the Chaman system with several meters of vertical offset. This transverse fault is sometimes called the Paghman fault.
- 1892, 20 December –
- 1935, 31 May – The 7.7
Moment magnitude scaleThe moment magnitude scale is used by seismologists to measure the size of earthquakes in terms of the energy released. The magnitude is based on the seismic moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of...
1935 Balochistan earthquake1935 Balochistan earthquakeThe 1935 Balochistan Earthquake occurred on May 31, 1935 at 3:02am at Quetta, Balochistan, British India . The earthquake had a magnitude of 7.7 Mw and anywhere between 30,000 and 60,000 people died from the impact. This ranks as one of the deadliest earthquakes that hit South Asia...
along the Ghazaband portion of the fault system killed upwards of 35,000 people. - 1978, 16 March – A 6.4
earthquake created a 5 km long rupture with up to 4 cm of left-lateral offset, and a smaller amount of vertical slip as the eastern wall of the fault dropped down.
External links
- Photograph of the surface expression of the Chaman fault by Hiroyuki Tsutsumi