New seismic research explains continental collision beneath Tibet

New seismic data collected by scientists at Stanford University and the Chinese Academy of Geological Sciences suggests that two competing processes are simultaneously operating beneath a collision zone in Tibet. This research contributes to an ongoing debate over the structure of the collision zone in the Himalaya region– the only place on Earth where continental plates continue colliding. The research marks the first time scientists have gathered credible images of along-strike or longitudinal variation in the Himalaya collision zone.

“The physical and political inaccessibility of Tibet has a limited scientific study, so most field experiments have either been too localized to understand the big picture or they’ve lacked sufficient resolution at depths to properly understand the processes,” said Simon Klemperer, a geophysics professor at Stanford’s School of Earth, Energy & Environmental Sciences.

Klemperer and his colleagues gathered seismic data that provided the first west-to-east view of the subsurface where India and Asia collide. The new images indicate that two competing processes are ongoing beneath the collision zone simultaneously: the movement of one tectonic plate under another, and the crust’s thinning and collapse.

The study was the first time researchers have gathered credible images of along-strike or longitudinal variation in the collision zone, Klemperer noted.

As the Indian plate collides with Asia, it forms Tibet– the tallest and biggest mountain plateau on the Earth. The process started about 57 million years ago, which was relatively recent in geological history.

Researchers proposed many explanations for its formation, including the thickening of the crust caused by the Indian plate gliding beneath the Tibetan Plateau.

They started the major logistical effort of mounting new seismic recorders in 2011 to resolve details that might have been overlooked. The new recorders were installed from east to west across Tibet.

The final images from recordings by 159 new seismometers spaced along two 997 km (620 miles) long profiles show where the Indian crust has deep cracks associated with the Himalayan arc’s curvature.

“We’re seeing at a much finer scale what we never saw before. It took a heroic effort to install closely spaced seismometers across the mountains, instead of along the valleys, to collect data in the west-east direction and make this research possible,” Klemperer said.

tibet-oct-16-2020

A wide area of baked ground shows the high temperatures due to rifting. Image credit: Simon Klemperer

tibet-oct-16-2020-3

Interpretive cartoon of processes currently operating in the India–Tibet collision zone. Image credit: Klemperer, et al.

As the Indian tectonic plate glides from the south, the mantle dips beneath the Tibetan plateau. The new data revealed that this process is causing small portions of the Indian plate to break off beneath two of the rifts, possibly creating cracks in the plate. The location of such fissures can be crucial for understanding how far a significant earthquake will spread.

“These transitions, these jumps between the faults, are so important and they’re at a scale that we don’t normally notice until after an earthquake has happened,” Klemperer added.

Using their seismic data, the scientists found an association between the occurrence of deep earthquakes and plate fissures. The study also explains why the strength of gravity varies in different areas of the collision zone. After the small pieces dropped off of the Indian plate, softer material bubbled up, producing mass imbalances in the India-Tibet collision zone, the researchers hypothesized.

“For geologists, this is the one big continental collision that is taking place on Earth today – it’s this natural laboratory where we can study these processes.”

Reference

“Localized foundering of Indian lower crust in the India–Tibet collision zone” – Shi, D. et al. – Proceedings of the National Academy of Sciences – https://doi.org/10.1073/pnas.2000015117

The deep structure of the continental collision between India and Asia and whether India’s lower crust is underplated beneath Tibet or subducted into the mantle remain controversial. It is also unknown whether the active normal faults that facilitate orogen-parallel extension of Tibetan upper crust continue into the lower crust and upper mantle. Our receiver-function images collected parallel to the India–Tibet collision zone show the 20-km-thick Indian lower crust that underplates Tibet at 88.5–92°E beneath the Yarlung-Zangbo suture is essentially absent in the vicinity of the Cona-Sangri and Pumqu-Xainza grabens, demonstrating a clear link between upper-crustal and lower-crustal thinning. Satellite gravity data that covary with the thickness of Indian lower crust are consistent with the lower crust being only ∼30% eclogitized so gravitationally stable. Deep earthquakes coincide with Moho offsets and with lateral thinning of the Indian lower crust near the bottom of the partially eclogitized Indian lower crust, suggesting the Indian lower crust is locally foundering or stoping into the mantle. Loss of Indian lower crust by these means implies gravitational instability that can result from localized rapid eclogitization enabled by dehydration reactions in weakly hydrous mafic granulites or by volatile-rich asthenospheric upwelling directly beneath the two grabens. We propose that two competing processes, plateau formation by underplating and continental loss by foundering or stoping, are simultaneously operating beneath the collision zone.

Featured image credit: Simon Klemperer

Tags: himalaya, research, tibet

Share:

Latest articles

Severe floods claim 47 lives, damage more than 900 000 ha of crops in Maharashtra, India

Heavy rains affecting parts of India over the past 7 days claimed at least 47 lives in Maharashtra and 50 in Telangana. In Maharashtra alone, more than 900 000 hectares (2.2 million acres) of crops have been damaged across state. 28 of the 47 people in Maharashtra…

New seismic research explains continental collision beneath Tibet

New seismic data collected by scientists at Stanford University and the Chinese Academy of Geological Sciences suggests that two competing processes are simultaneously operating beneath a collision zone in Tibet. This research contributes to an ongoing debate over…

At least 12 people dead after heavy rains trigger flooding in Dar es Salaam, Tanzania

At least 12 people lost their lives after heavy rain and flooding hit Dar es Salaam, Tanzania overnight Tuesday to Wednesday, October 13 to 14, 2020. The deaths occurred in Ilala and Kinondoni Police Zones, Dar es Salaam Special Zone Police Commander Lazaro…

The Weekly Volcanic Activity Report: October 7 – 13, 2020

New activity/unrest was reported for 1 volcano from October 7 to 13, 2020. During the same period, ongoing activity was reported for 16 volcanoes. New activity/unrest: Klyuchevskoy, Central Kamchatka (Russia). Ongoing activity: Aira, Kyushu (Japan) | Dukono,…

Death toll jumps to 77 as unseasonal, record rains hit parts of India

Heavy rains affecting parts of India, including Telangana, Maharashtra, and Karnataka this week claimed the lives of at least 77 people by October 16, 2020. Meteorologists described the rains as rare and unseasonal. At least 50 people have died in Telangana, many of…

Cameron Peak Fire grows to largest in Colorado’s history

The Cameron Peak Fire started on August 13, 2020, on the Arapaho and Roosevelt National Forests near Cameron Pass and Chambers Lake in Colorado. By October 14, it surpassed both the 2002 Hayman and 2020 Pine Gulch fires to become the largest wildfire in history…

Extreme drought drains Paraguay River to its lowest level in 50 years

The Paraguay River is now on its lowest level in 50 years as the region is reeling from months of extreme drought. The drop in water levels slowed down cargo vessel traffic, resulting in cost overruns for imported goods and a loss of 250 million dollars. The river…

Southern New England hit by a rare derecho, NWS confirms

The unusually powerful storm in Southern New England last week, October 7, 2020, was a rare derecho, the National Weather Service (NWS) confirmed. The storm killed at least two people, left more than 200 000 customers without power, caused damage to a 515 km (320…

Asteroid 2020 TE5 flew past Earth at 0.15 LD

A newly-discovered asteroid designated 2020 TE5 flew past Earth at a distance of 0.15 LD / 0.00038 AU (56 847 km / 35 323 miles) at 18:18 UTC on October 9, 2020. This is the 75th known <1LD asteroid of the year. Asteroid 2020 TE5 was first observed at ATLAS-HKO,…

Tropical Storm “Nangka” makes landfall in Vietnam just three days after Linfa

Tropical Storm “Nangka” made landfall in northern Vietnam at around 06:00 UTC on October 14, 2020. Nangka is the 16th named storm of the 2020 Pacific typhoon season. The storm hit land just 3 days after Tropical Storm “Linfa” — further…

At least 13 killed as worst rains in more than 100 years flood Hyderabad, India

A deep depression that crossed Andhra Pradesh coast near Kakinada on Tuesday, October 13, 2020, brought unprecedented rainfall over Hyderabad, capital of the Indian state of Telangana, from Tuesday night to Wednesday morning, claiming the lives of at least 13…

China sees historical 21 large-scale floods and national average rainfall in 2020

China has seen 21 large-scale floods in 2020, 1.6 times more than that of past years, hitting a record since 1998. This year’s national average rainfall of 616 mm (24 inches) is 13% more than the same period in 2019, setting the record for second-highest since…

New mass deaths of sea animals discovered off Russia’s Kamchatka

Authorities reported Monday, October 12, 2020, that a new mass die-off of marine animals has been discovered off the coast of Russia’s Kamchatka, where mysterious toxic pollution along a 40 km (25 miles) stretch recently killed 95 percent of seabed animals and…

‘Extremely rare’ red auroras seen for two nights in a row over Finland

Extremely rare red auroras were seen over Utsjoki, Finland, on Monday and Tuesday, October 12 and 13, 2020. These natural light display, also referred to as northern lights, are normally green. However, for some reason, the solar wind on Monday excited oxygen at…

Death toll climbs to 29, over 130 000 houses flooded in central Vietnam

At least 29 fatalities have been confirmed in central Vietnam as of Tuesday morning, October 13, 2020, after prolonged heavy rains triggered destructive floods and landslides. 12 others remain missing, more than 130 000 houses have been inundated, and wide swaths of…

Darwin records highest October daily rainfall since 1941 – Northern Territory, Australia

Northern Territory’s capital Darwin was hit by up to 177 mm (7 inches) of rainfall on Thursday, October 8, 2020– the city’s highest daily rainfall for October since record-keeping began in 1941, the Bureau of Meteorology (BOM) confirmed. The agency added…

Air still leaking from ISS after failed attempt to seal the crack

Pressure continues to decline at the International Space Station after a failed attempt to fix the air leak using adhesive tape. The leak is located the working compartment of Zvezda Service Module and was described by Roscosmos as ‘more than standard.’ The…

This content was originally published here.



0 0 vote
Article Rating
Subscribe
Notify of
0 Comments
Inline Feedbacks
View all comments