Featured Research

from universities, journals, and other organizations

'Caldas tear' resolves puzzling seismic activity beneath Colombia

Date:
June 6, 2013
Source:
Seismological Society of America
Summary:
Colombia sits atop a complex geological area where three tectonic plates are interacting, producing seismicity patterns that have puzzled seismologists for years. Now seismologists have identified the "Caldas tear," which is a break in a slab that separates two subducting plates and accounts for curious features, including a "nest" of seismic activity beneath east-central Colombia and high grade mineral deposits on the surface.

This is a tectonic map of northwestern South America and Panama showing plate boundaries and neotectonic fault systems and selective distribution of hypocentral solutions of ~30,000 earthquakes extracted from the entire catalog of the CNSN.
Credit: BSSA

Colombia sits atop a complex geological area where three tectonic plates are interacting, producing seismicity patterns that have puzzled seismologists for years. Now seismologists have identified the "Caldas tear," which is a break in a slab that separates two subducting plates and accounts for curious features, including a "nest" of seismic activity beneath east-central Colombia and high grade mineral deposits on the surface.

In a paper published in the June issue of the Bulletin of the Seismological Society of America (BSSA), researchers Carlos Alberto Vargas of the Universidad Nacional de Colombia and Paul Mann of the University of Houston relied on recorded earthquake data from the Colombian National Seismological Network database and tomographic data to reveal a clearly defined, prominent tear.

"This paper attempts to provide a unifying concept of how the deformation is proceeding on a regional scale in Colombia," said Mann.

The complex regional tectonic activity includes movement of three plates: the Caribbean plate that is subducting or being forced beneath Colombia in the north; the Panama block or Panama plate that is colliding with Colombia in the central part of the country; and the Nazca plate, which is an oceanic plate that is subducting beneath the southern part of Colombia from the Pacific.

While Colombians have experienced earthquakes in the past 20 years, none has been exceedingly large, despite the complex zone of convergence beneath it.

"Unlike the high seismicity to the south of the Caldas tear, there are few destructive earthquakes north of the tear, which suggests that there is an accumulation of stresses that could trigger strong motion events resulting from the frontal collision of the Panamanian Arc against Colombia," said Vargas.

The authors used the Colombian Seismic Network's database of more than 100,000 seismic events to identify the prominent tear, where the slab is broken along a very distinct break, separating the Nazca oceanic plate, which is coming from the Pacific, from the Panama plate, which is an old island arc (Sandra ridge) that pushes into Colombia from the west.

"We think that this Panama block is acting as an indenter. It's a block of thick crust that doesn't subduct easily, rather it subducts at a shallow angle," said Mann. "And because it's thick crust, it acts like a fist or an indenter that's pushing into the whole country of Colombia and northwest South America."

Vargas and Mann suggest the crust that preceded the indenter or colliding Panama block is being ripped apart from the indenter, which is crust that cannot easily subduct. The Caldas tear forms the southern edge of the indenter, separating it from the Nazca plate. The indenter is breaking from the crust that preceded it, forming the Bucamaranga nest, which is a dense area of seismic activity in a small volume of crust at about 140 km depth.

Using tomographic data, the authors inferred that the Caribbean plate crust to the north is subducting at a very shallow angle and producing relatively little deep seismicity. Tomography is a way to map the geometry of a subduction zone on the basis of differences in the seismic attenuation of crusts. Colder subducting crust, for example, will have a lower attenuation than the surrounding mantle. The Caribbean plate in the north is subducting at a slower rate than the Nazca plate in the south, where seismic activity is greater.

"In the center of it all is the indenter -- an incredibly important feature for Colombia and for assessing its earthquake hazard," said Mann.

Colombia features large strike slip faults that form a V-shaped pattern, which is symmetrical about the Panama plate. Vargas and Mann relate the upper crust strike slip faults to the indenter, which they suggest is pushing the crust further east than in areas in the north and south.

The Caldas tear is reflected in the landscape. The Magdalena River, which runs northward, changes from broad valleys to steeper relief gorges as it crosses the tear, suggesting to researchers that the tear may propagate to the surface. There is an alignment of small volcanoes along the tear that have an unusual composition, distinctly different than seen in the volcano arc in the south.

"We have found that this tectonic structure not only controls the distribution of major mineral deposits, but has also come to control the geometry of several sedimentary basins, and the distribution of hydrocarbons retained in them," said Vargas.

"Tearing and breakoff of the subducted slabs as the result of a collision of the Panama arc-indenter with northwestern South America," appears in the June 2013 issue of BSSA.


Story Source:

The above story is based on materials provided by Seismological Society of America. Note: Materials may be edited for content and length.


Cite This Page:

Seismological Society of America. "'Caldas tear' resolves puzzling seismic activity beneath Colombia." ScienceDaily. ScienceDaily, 6 June 2013. <www.sciencedaily.com/releases/2013/06/130606101728.htm>.
Seismological Society of America. (2013, June 6). 'Caldas tear' resolves puzzling seismic activity beneath Colombia. ScienceDaily. Retrieved April 23, 2014 from www.sciencedaily.com/releases/2013/06/130606101728.htm
Seismological Society of America. "'Caldas tear' resolves puzzling seismic activity beneath Colombia." ScienceDaily. www.sciencedaily.com/releases/2013/06/130606101728.htm (accessed April 23, 2014).

Share This



More Earth & Climate News

Wednesday, April 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

California Drought Is Good News for Gold Prospectors

California Drought Is Good News for Gold Prospectors

AFP (Apr. 22, 2014) For months California has suffered from a historic drought. The lack of water is worrying for farmers and ranchers, but for gold diggers it’s a stroke of good fortune. With water levels low, normally inaccessible areas are exposed. Duration: 01:57 Video provided by AFP
Powered by NewsLook.com
Raw: MN Lakes Still Frozen Before Fishing Opener

Raw: MN Lakes Still Frozen Before Fishing Opener

AP (Apr. 22, 2014) With only three weeks until Minnesota's fishing opener, many are wondering if the ice will be gone. Some of the Northland lakes are still covered by up to three feet of ice, causing concern that just like last year, the lakes won't be ready. (April 22) Video provided by AP
Powered by NewsLook.com
Is North Korea Planning Nuclear Test #4?

Is North Korea Planning Nuclear Test #4?

Newsy (Apr. 22, 2014) South Korean officials say North Korea is preparing to conduct another nuclear test, but is Pyongyang just bluffing this time? Video provided by Newsy
Powered by NewsLook.com
Nasa Gives You An Excuse to Post a Selfie on Earth Day

Nasa Gives You An Excuse to Post a Selfie on Earth Day

TheStreet (Apr. 22, 2014) NASA is inviting all social media users to take a selfie of themselves alongside nature and to post it to Twitter, Facebook, Flickr, Instagram, or Google Plus with the hashtag #globalselfie. NASA's goal is to crowd-source a collection of snapshots of the earth, ground-up, that will be used to create one "unique mosaic of the Blue Marble." This image will be available to all in May. Since this is probably one of the few times posting a selfie to Twitter won't be embarrassing, we suggest you give it a go for a good cause. Video provided by TheStreet
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins