Chris Rowan is a geologist specialising in the dark arts of paleomagnetism, and getting people to pay him to travel to exotic destinations for fieldwork. Having drilled up New Zealand during his PhD, and South Africa in his first post-doc, he now works at the University of Edinburgh.
Anne Jefferson has a love of all things water-related and blends hydrology, geomorphology, geology, and climate change in her work. She has a Ph.D. from Oregon State University and is now an assistant professor at the University of North Carolina at Charlotte.
A magnitude 7.0 earthquake struck Haiti this evening, causing extensive damage to the capital, Port-au-Prince, and probably causing many casualties. The map below shows where the main shock occurred (red), as well as the epicentres of the numerous aftershocks (orange) that occurred in the following 5 or 6 hours (and continue even as I write).
The main shock appears to have initiated less than 25 km southwest of Port-au-Prince; this close proximity meant that the city would have endured the maximum possible shaking intensity from an earthquake of this size, leading to extensive damage. Here's the focal mechanism, courtesy of the USGS:
With the help of my recent post on focal mechanisms, it is hopefully obvious that the rupture occurred on a primarily strike-slip fault, with the crust on each side of the fault moving horizontally relative to the other side. To understand why there is strike-slip faulting in this area, we need to step back, and look at a simplied map of the entire Caribbean:
The Caribbean is contained on its own separate little plate; a rather diminutive part of the tectonic jigsaw that is the Earth's crust. It is surrounded on three sides by the much larger North and South American plates, both of which are moving approximately westwards with respect to the Caribbean plate at around 2-3 centimetres a year. On the eastern edge of the plate, the boundary runs perpendicular to the direction of relative plate motion, so there is compression and subduction (and subduction volcanism, exemplified by the likes of Montserrat). However, as the boundary curves around to form the northern boundary of the Caribbean plate, where the Haitian earthquake occurred, it starts to run parallel to the direction of relative plate motion, making strike-slip faulting along E-W trending faults the most likely expression of deformation in this region. This is exactly what the Haitian quake appears to record.
Note also that deformation across the northern plate boundary appears to be distributed - some motion is accommodated on faults that are located a little bit away from the actual plate boundary, further inside the plate interior. The Haitian quake appears to have occurred on one of these faults: based on the position of its epicentre the rupture is extremely close to the Enriquillo Fault, which appears to be a major strike slip fault running across the southern end of Haiti. This is the fault most likely to have ruptured.
Tectonic map of the Northern Caribbean (Source)
There is nothing particularly unusual about this earthquake given the tectonic context. Unfortunately, however, Haiti is a very poor country - one of the poorest and least developed in the world - so unfortunately, its government was not in a position to really do much to prepare for the inevitable large earthquake, leaving tens of thousands to suffer the consequences.
Geotagging (View all geotagged posts)
Update from Anne: Chris has been featured in a Nature News Briefing: "The Haiti Earthquake in Depth" along with more information about the faults in question and the known seismic risk of the area.
Further updates:
Haiti's seismic future
What next for the Enriquillo Fault?
Environment
Physical Science
Comments
Excellent overview, Chris. I'll be using it in class in a few hours.
Posted by: Ron Schott | January 13, 2010 2:59 AM
Radio 4 couldn't contact you this morning, so they grabbed someone else from Edinburgh. He said that in the long term there might be aftershocks to the west, e.g. in Jamaica. is this just because most of the fault is to the west, or is there a deeper reason?
Posted by: Bob O'H | January 13, 2010 3:04 AM
Excellent post, Chris. Thanks for writing this.
Posted by: Arikia | January 13, 2010 3:20 AM
Excellent, clear post.
Posted by: Pyers Symon | January 13, 2010 4:06 AM
Thank you Chris this is a very very clear blog site. I can understand a lot more now. Please take care. My thoughts are of the people of Haiti.
Posted by: Deb | January 13, 2010 5:32 AM
Fantastic post, Chris. I think my hydrogeology students will be getting a little dose of tectonics today thanks to your clear explanation.
Posted by: Anne Jefferson | January 13, 2010 6:11 AM
Very nice post!! Enriquillo fault was the first thing I though of as soon as I saw the location of the epicenter. I think that of all the Caribbean islands, Hispaniola is one of the more messed up, tectonically, part of the north is even moving in the opposite direction as the rest of the island.
Posted by: Jorge Velez-Juarbe | January 13, 2010 6:23 AM
Quick, clear work! Thanks, Chris!
Posted by: Callan Bentley | January 13, 2010 7:43 AM
Excellent post. I had also written something and have just added a link to this clear explanation. Thanks.
Posted by: Filipe M. Rosas | January 13, 2010 7:50 AM
Thanks Chris; You have posted a comprehensive overview of the massive earthquake attacked last evening to Haiti. But think we should help them any possible way at least pray for them.
Posted by: DrKeithCurrie | January 13, 2010 9:17 AM
Thanks, Chris - and great explanation.
Posted by: Kim | January 13, 2010 10:20 AM
Thank-you! Quick, clear, and simple.
Posted by: Dixie McCormick | January 13, 2010 10:30 AM
He said that in the long term there might be aftershocks to the west, e.g. in Jamaica. is this just because most of the fault is to the west, or is there a deeper reason?
I don't know for sure, but it may be historical ruptures on this fault were further to the east, so the west is where the most stored elastic strain is waiting to be released.
Posted by: Chris Rowan | January 13, 2010 10:35 AM
I'm gonna get on the bandwagon here ... great post, exactly the information I wanted to know about this event.
Posted by: BrianR | January 13, 2010 10:44 AM
For some reason I was trying to google "tectonic plates Haiti earthquake" before I went "duh! I bet Chris has it" - and lo and behold I was right! You answered everything I wanted to know - great job!
Posted by: Erin | January 13, 2010 11:35 AM
Great post, it's nice to learn the science behind the earthquake. As you pointed out, Haiti is a very poor country with few resources to help recover from this event. If people would like to help there are a variety of organizations they can donate to. I like Mercy Corps https://donate.mercycorps.org/
Posted by: Laurel | January 13, 2010 12:03 PM
Has there been an upthrust of land?
Just noted on the BBC live update page that at 1733:
My italics.http://news.bbc.co.uk/2/hi/americas/8456322.stm
Posted by: chezjake | January 13, 2010 1:02 PM
Structural geology enthusiasts: Looks like a perfect example of plate interaction in transpression.
Posted by: Maitri | January 13, 2010 1:11 PM
It's too bad Haiti has been denuded of trees, unlike the DR. Result: few wooden buildings, too many brick/masonry buildings. I would bet that's the main cause of casualties.
Posted by: Roland | January 13, 2010 3:28 PM
Good post but a comment on "maximum shaking".
If the aftershock and mainshock locations are correct, then the earthquake ruptured from east to west and away from Port-au-Prince. This would mean the maximum possible shaking did NOT occur in the city but likely at the west end of the fault due to directivity effects (which can be significant).
When a large earthquake occurs, the rupture begins at one point and then progresses along the fault, usually at about shear wave velocity (perhaps 2 - 3 km/s). Seismic waves radiated in the direction of the rupture propagation tend to have higher amplitudes than the waves moving in the opposite direction. In the case of the Haiti earthquake, the location of the mainshock denotes the likely nucleation point and the aftershocks will be (typically) clustered along the total rupture. Therefore, *if* the locations on the map are correct, the earthquake started in the east and the fault ruptured along a line to the west.
That said, ground motion also depends on site conditions - if much of the city was built on soft soil rather than bedrock, this would likely increase shaking.
In general, maximum shaking does not always occur near the fault.
http://earthquake.usgs.gov/regional/nca/rupture/directivity/
Posted by: rm | January 13, 2010 3:45 PM
Thank you. Excellent explanation.
Posted by: Alan B | January 13, 2010 5:05 PM
Anyone know how long the quake lasted?
Posted by: steve | January 13, 2010 5:41 PM
I wanted to get your opinion on whether the Earthquake which happened in Northern California (N. American plate) triggered the movement of the Carribean/N. American plates to result in the Haitian quake.
Posted by: Kitty | January 13, 2010 6:50 PM
We haven't heard any reports from Jamaica or Cuba of quake effects. Is this because it is a relatively small quake, or is it simply that slip occurred along a very small portion of the fault?
Posted by: bo | January 13, 2010 7:10 PM
@chezjake: The motion along that plate boundry has been mostly left-lateral strike-slip since the Cretaceous. That is also what is seen along the Montagua fault in Guatemala. However, Cretaceous limestone is also exposed there with a little additional uplift on the north exposing low-grade metamorphics.
http://sp.lyellcollection.org/cgi/content/abstract/328/1/219
Posted by: Dave Crane | January 13, 2010 7:26 PM
We haven't heard any reports from Jamaica or Cuba of
quake effects. Is this because it is a relatively small
quake, or is it simply that slip occurred along a very
small portion of the fault?
The earthquake originated at shallow depth. That reduces areal coverage, but then ground motions are more violent where it is felt.
Posted by: zeke | January 13, 2010 7:33 PM
@kitty: Fault movement in California doesn't affect the faults in the Caribbean. Too far away and too many faults in between that would have been subjected to far greater stress - or absorbed it. This earthquake was predicted, based on local tectonics, in 2008 at a Caribbean Geological Congress by Paul Mann, (et al,) of the University of Texas. "Since the last major event in south-central Dominican Republic was in 1751, that yields ~2 meters of accumulated strain deficit, or a Mw=7.2 earthquake if all is released in a single event today. The two largest cities within 30 km of the fault zone are Port-au-Prince, Haiti, and Kingston, Jamaica, with a combined population of 3.65 million inhabitants."
See http://www.ig.utexas.edu/jsg/18_cgg/Mann3.htm
Posted by: Dave Crane | January 13, 2010 7:36 PM
@zeke: It was felt in Jamaica, but the fault does not seem to have released that far from Haiti. Jamaica is next on the watch list; the quakes are occurring from west to east after several hundred years of stress accumulation. http://sflcn.com/story.php?id=7734
Posted by: Dave Crane | January 13, 2010 7:43 PM
Thanks Zeke, my geology is rusty. Just a note: Haiti is the same size as the county I live in; we have fewer than 40,000 inhabitants. I can't imagine stuffing nearly 10 million people into the same space. That seems like a disaster in itself. I feel badly for Haitians and all other human beings living in those conditions.
Posted by: bo | January 13, 2010 7:56 PM
I totally agree Bo, we are over populated...and some long term plan needs to be formulated...
Posted by: Bulletproof vests | January 13, 2010 8:22 PM
I dont know if we are over populated at this time....but we are getting very close. China, india, philipines, and haiti are all very dense population centers...before long we will not be able to feed them.
Posted by: Rabbit Cages | January 13, 2010 8:26 PM
Population control: two words that send many people into an irrational preference for high casualties in natural disasters, including famine. Nature will continue with mathmatical risk management: quantity versus quality.
Posted by: bo | January 13, 2010 9:22 PM
tank's, it's an example of plate interaction in transpression.
Posted by: Nicolas Gomez | January 13, 2010 10:02 PM
Tectonics, Schmectonics. Pat Robertson, that font of gentle wisdom KNOWS it was some pact with the devil.
So much for your SCIENCE ...
Posted by: percyF | January 14, 2010 1:46 AM
Thanks Chris, I really appreciate ur posting. Kus-Indonesia
Posted by: kuswantoro | January 14, 2010 4:09 AM
Thank you for a great post. I just found your blog but will continue to follow.
Posted by: Tracy Barnhart | January 15, 2010 8:29 AM
what type of earthquake was it that happend and why?
Posted by: kip | January 15, 2010 8:56 AM
Very good, precise analysis of the situation. One thing that I wanted to ask was if this may be a "Montserrat" in the making? Could there be more than just quaking going on? Could there be a volcanic eruption coming soon for that island? Perhaps the governments involved in the recue of people should be considering evacuations instead? Thank you and continued success in your field.
Posted by: Molly Roberts | January 15, 2010 9:34 AM
Thanks; good explanation. The Haitian part of Hispaniola seems to be multiply accretionary and sitting right on top of several jammed subduction zones (the active transform fault on which the earthquake occurred intersecting one of them.) What, if anything, does this suggest about current and future tectonic activity in the region?
Posted by: FC | January 15, 2010 10:19 AM
Do you think the North American plate will push back on the Caribbean plate and cause activity on the other side of the plate?
Posted by: Toni | January 15, 2010 10:58 AM
It seems Mann et al. (2008) had predicted that an event of such magnitude might occur.
Here is the link to the abstract of the presentation given at the 18th Caribbean Geological Conference.
Posted by: Jorge Velez-Juarbe | January 15, 2010 12:06 PM
Here's an interactive map of the Caribbean plate
Posted by: Chris Lockyer | January 15, 2010 12:58 PM
Clearest of any of the articles I have seen. Thanks
Posted by: Mike (UK) | January 16, 2010 4:38 AM
Awesome explanations! I was wondering if this had anything to do with the earthquake that took place in the Gulf of Mexico a couple of years ago. I didn't think there were any faults there and this earthquake was felt (mostly) in western FL (Tampa Bay area). Could there be something bigger coming for FL? I've always thought that FL was immune to earthquakes, could I be mistaken?
Posted by: Leanne Flynn | January 16, 2010 6:08 AM
Is it possible to know when the aftershocks will stop in Haiti and is it possible for Haiti to get hit by a similar quake in the upcoming years?
Posted by: Tito | January 16, 2010 8:13 AM
@38 Molly, rest assured this quake is no way related to any volcanism
Posted by: EKoh | January 16, 2010 5:44 PM
could you explain to me what the red dots mean?
Posted by: hanny m | January 16, 2010 10:08 PM
Thank you for this information. I am in the North of Haiti where we felt the earthquake but not nearly as bad. This is helpful in explaining what happened to many terrified people. I have 2 questions... 1. the red dots on the one map that almost cover Jamaica, is that pressure build up that it is showing or what? 2. What are the chances that the northern fault will rupture soon? I am hearing reports that it could rupture tomorrow or in 100 years... do you have any more details?
Thank you!
Posted by: Judy | January 17, 2010 4:26 PM
giving the fact that haiti lies in a risk zone,it should have been one of the priorities of the government to see that good housing standards are in place so as to be prepared for such eventualities.moreover the people have added to these due to the fact that this country has been in very unstable governments for a long time and as such proper planning has not been in place.a magnitude earthquake of 7 and a population of 3 million which has been affected cannot cope with the fact that only a single airport with a single runway is used to mobilise efforts.this is a really worrisome situation and needs to proper strategic planning to rebuilt the country
Posted by: WILLIAM CHE | January 17, 2010 5:54 PM
the number of aftershocks shows that the rate of destruction on the plate was so massive and as such the effects radiated outwards and as such this destruction.also am not sure an erruption can occur in haiti since subsidence might have already occured in a large scale due to this massive quake.however,out mathematization can be ignored by nature.
Posted by: william che | January 17, 2010 6:02 PM
Some comments on construction, which have been referenced above. Haiti's primary location puts it in the path of hurricanes which makes earthquake codes very hard to enforce due to the danger of death from wind damage and flooding. The usual construction is concrete and from the photographic evidence it looks like the shaking was severe enough to shatter concrete strucutres with steel reinforcement. As Kobe, Jp proved in a similar sized quake in January 1994, this kind of construction leads to high loss of life.
Question for the geologists out there. This quake is on the same plate boundary as the Honduran quake (7.5) which occured in Q-1 2009 I believe?
Second question, I haven't heard (23 feet?)the amount of stored plate (since last major quake on Enriquillo fault in 1770) movement. Has there been an actual movement calculation posted yet?
Posted by: Orlando | January 18, 2010 12:17 AM
awesome artcle on the haiti earth quakes
Posted by: brieanna miller | January 20, 2010 9:04 AM
I am going to montego bay jamaica in february is this a good idea? Im worried about earthquakes, tsunamis, etc.
Posted by: chris | January 20, 2010 10:35 AM
I think you will be ok down there...there will not be any more earthquakes for a little while. go to Jamaica and have a great time. I wouldnt let the small possibility of a earthquake ruin your vacation. Have fun and drink some rum and listen to bob marley.
Posted by: Rock Tumblers | January 21, 2010 10:07 PM
Do you know that your post is being used in conspiracy theory propaganda? (Unfairly, of course)
http://onlinejournal.com/artman/publish/article_5495.shtml
...Despite the fact that Rowan sees this as a “strike-slip in the Caribbean Plate with the crust on each side of the fault moving horizontally relative to the other side,” and so on, I still feel that the pinpointing of Haiti is not just another predictable earthquake. But read Chris’s full explanation. A bolt of HAARP energy could have caused that “strike-slip.”...
Posted by: Lena | January 22, 2010 6:28 PM
Wow. I'm "official". Who knew? Perhaps the government beamed the notion to research and write a post directly into my head.
I do love the idea of a weapon that can cause hurricanes and earthquakes. Them being so similar and all.
Thanks for all the other comments/questions. I might write a follow-up post to address the latter.
Posted by: Chris Rowan | January 23, 2010 4:03 PM
As a native Barbadian, and middle school science teacher living in South Carolina, US, I found this site the most helpful in understanding the tectonics underlying the Haitian earthquake. I did not realize that there was a microplate (Gonave) in the northern Caribbean.
The western edge of the Gonave Plate, a divergent boundary, suggests eastern movement. However, the directional arrow as indicated on the eastern portion of the plate along the Enriquillo Fault, which ruptured, (Tectonic Map of the Northern Caribbean) shows a westerly movement of the microplate.
Question#1: Is the Gonave microplate a fractured portion of the Caribbean Plate? If so, how was it created?
Question #2: Which type of movement/interaction occurred to cause the Haiti earthquake. Was it the two plates moving in opposite directions along the lateral fault? Or were they moving in the same direction, but at different rates?
Thanks for any help in addressing these questions. My students are eager to know!
Posted by: EJ | January 24, 2010 7:18 AM
Based on my limited geology experience, the aftershocks should spread around the main shock. To me Haiti situation looks like another HAARP intiative - 200,000 blacks gone. You geologists are really strange - those people working in HAARP will be laughing their butt off. You always have plate tectonics for every disaster where people die in mass...
Go to youtube and search for Jesse Venturas video on HAARP. You can also get videos on HAARP relation to Haiti. By the way if u dont know Jesse Ventura is the only independent elected by americans - not the bull shit democrats and republicans (both sides of the same coin).
Chris - i think u are a nerd, like many scientisits. Your simple explanation and animations on google earth appeals for people with some scientific knowledge. But do u realize that there are earthquakes that occur without any "nature" intervention.
Did u ever heard that about a year ago, a new oil field was discovered in Haiti !!!!!!!!!!!!!!!
Posted by: HAARP | January 24, 2010 2:29 PM
OK, this is notice that any more comments referencing this HAARP rubbish will be summarily deleted. Put your energy into doing something useful for the Haitians instead. But I can't let this one slide:
Based on my limited geology experience, the aftershocks should spread around the main shock
Oh really? 'Limited', indeed.
Posted by: Chris Rowan | January 24, 2010 3:40 PM
Oh, yes, there are also some excellent questions from EJ to answer:
Question#1: Is the Gonave microplate a fractured portion of the Caribbean Plate? If so, how was it created?
That's a pretty good way of describing it. Because the motion across the plate boundary is distributed across several fault systems, you get fault bounded-slivers that can be treated as independent 'microplates' with their own slightly different motion vectors. It's just an expression of the plate boundary in this region being wider than a single fault.
Question #2: Which type of movement/interaction occurred to cause the Haiti earthquake?
Because of the motion being accommodated on the Enriquillo-Plantain Garden (EPG) fault system, the Gonave sliver is moving east relative to the North American plate slightly more slowly than the rest of the Caribbean plate, so there is a net eastward motion of the crust to the south of the EPG zone relative to the crust in the north. This results in left-lateral, of sinistral, strike slip deformation at the fault itself, consistent with the focal mechanism.
Hope that makes sense to you and your students.
Posted by: Chris Rowan | January 24, 2010 7:17 PM
It would seem that at the other end of the Caribbean chain Trinidad is in a similar situation and is stradling the plate boundary just after it turns east/west to run along the Northern regions of South America. There are also several strike/slip faults, El pilar, Cloche, etc. defining this boundary. It would seem that northern Trinidad is sliding past the south of the island. Can we expect "a big one" in Trinidad some time in the future?
Posted by: Ivor St Hill | January 25, 2010 11:05 AM
Execcelent work. The quake was predicted in 2008 at 18th Carinean geological conference. But somehow the conference prediction were just filed. Let use science wisely. What is future hold now for Jaimaca?
Patrick Kamau-Kenya
Posted by: patrick | January 26, 2010 8:08 AM
I am thinking of going to Jamaica next month, either Montego Bay or Negril, what are the chances of an earthquake occuring there, given the recent one in Haiti>
Posted by: Michele Madick | January 26, 2010 11:15 AM
Thanks for the post Chris. This is really helpfull because my homework is on how the earthquake in Haiti happened and this is very good.
Posted by: Jake | January 26, 2010 1:05 PM
Thanks for the post Chris. This has really inspired me a lot to study more about seismology and understanding tectonics but it is always good to learn about earthquake and painful to bear the consequences.I pray for the people who have lost there family and house
Posted by: Shravanee | January 28, 2010 1:47 AM
We just started to donate 1$ from each purchase to Haiti quake survivors.
Thanks to all good people.
Posted by: Andrew | January 28, 2010 10:04 AM
i hear that chicago next to have a earthquake,.
Posted by: dyani | January 30, 2010 3:27 PM
how many aftershocks happened in haiti
Posted by: eric luther | February 2, 2010 9:12 AM
OMG an earthquake will not happen in chicago you people.yaaaaaaa
Posted by: diana castro | February 7, 2010 8:36 PM
Chris:
Your post is very impressive! What do you think is a risk of an earthquake in Negril Jamaica ?
Posted by: Walter | February 11, 2010 7:05 PM
excellent work. great answer
Posted by: shazia | February 14, 2010 1:02 PM
I would love 2 see happen when the earthquake hit hitis
Posted by: shaqwanda eubanks | February 17, 2010 10:59 AM
what a shame thing that happened to Haiti,but i have heared thet people around the world are helping the Haitian people.It's a good thing that people around the world have hearts..keep up the good work..
Posted by: matete | February 17, 2010 3:35 PM
thanks, very useful info
Posted by: Frumusete | February 20, 2010 2:14 AM
fanks mate, that was very helpful 4 my geograthy homework!!
Posted by: joshua | February 20, 2010 5:13 PM
this was just what i wanted for my geography project thanks dude
Posted by: khuzi | February 22, 2010 10:32 AM
I have been in Bon Repos, Haiti for a month now since the quake as humanitarian relief, although supposedly there have been quite a few aftershocks. Early tuesday morning at 126am I felt 2 pops then I heard something like a freight train the 2nd floor of the structure which I am staying in began to shake violently as I heard 4 pops while trying to egress via the outside staircase. 10 minutes later we felt another tremor. We had already felt 3 in Bon Repos Monday morning. It has been quiet for 3 wks, is the plate slipping again? Should we be prepared for a larger quake/aftershock with this new combined activity originating from practically the same epicenter as the 12 January Quake?
Posted by: Missy | February 24, 2010 2:06 AM
haiti might be unlucky last time this happened 20 years later haiti was hit by a bigger earthquake, at the moment this is what worries scientist the fault line didnt break the surface and they recon that next time it will and with bigger shocks,
Posted by: douglas randall | February 24, 2010 4:26 PM
Ok. Since Wednesday night February 24 here in Bon Repos, Haiti we have felt a continuous stream of gentle shakes. Most coming every 15 seconds sometimes they are longer and more prominent but not very strong. This has been going on for 3 days since monday and tuesday's numerous aftershocks. What do they mean?
Posted by: Missy | February 26, 2010 7:37 PM
Excelent work, it it is really educative and the images are good.
Posted by: pariuri sportive | March 2, 2010 2:13 PM
This helped me alot for schoo!!! thatnk you!!!!!!!:)
Posted by: claire | March 2, 2010 8:53 PM
thanks for the information x
oh hey claire :)
Posted by: amz | March 4, 2010 6:37 AM
Thanks for the information but why did the haiti earthquake kill so many people??? It for school and the rest of the information has helped me a lot, thanks for everything. x :)
Posted by: Keely Taylor | March 6, 2010 6:16 AM
this was for my homework in sience
Posted by: kewl | March 7, 2010 4:32 PM
This website was siccccck :)
It helped me greatly with my Geography task.
Thanks baaabe :) xxxxxxx
Posted by: Harry :) | March 9, 2010 7:00 AM