Seismic Activity

         There were several reasons I decided I wanted to focus on Bangladesh for this semester, first and foremost, it is located on the Indian sub-continent, the geology of which has always fascinated me. One of the other reasons I chose Bangladesh was that the country has one of the largest human populations in the world. It is ranked 9^th in the world with a population of approximately 166,280,712. When you combine natural disasters with so many humans, things get interesting on the Mercalli scale. I have found in the past research projects that the people on this continent are plagued with a variety of natural disasters which might otherwise be avoidable if they were to take some basic precautionary measures. However, it is not as simple as it sounds. With countries like India, Bangladesh and Nepal, although they are densely populated they are often also years behind modern infrastructure and in many areas these countries are remain extremely rural. I spent several weeks in Nepal and it constantly boggled my mind that most of the people I came across were extremely resourceful and intelligent but none of the roads were paved, rice paddies were clearly built in areas prone to massive flooding and it was pretty obvious most of the time that the villages were regularly getting uprooted by natural disasters only to re-settle in another hazardous zone. Bangladesh is no different from the outside looking in. Like many settled areas of the Indian and Asian sub-continents, it is built in a river valley on the Ganges Delta and sort of nestled amongst all the water-sources of the Bay of Bengal. It makes logical sense that a settlement would be made in such an area because the soil would be rich and fertile and the people who farm the land can rely on yearly flooding to irrigate their crops. On the other hand, in contemporary retrospect it is perhaps not the best place for millions of people to build their houses and livelihoods. Already knowing of the aforementioned factors, I assume that Bangladesh, although it has a more advanced urban infrastructure than Nepal (for example) is probably often uprooted and forced to rebuild quickly, with limited economic means and potentially inadequate materials to withstand a much greater disaster such as a major earthquake.

My primary source for this entry was a paper titled Earthquake in Bangladesh: A Natural Disaster and Public Awareness and while it was published some time ago (December 2001, to be exact) its information still seems to be relevant as I found many repeats and quotes taken from it while I continued my search for information.

Bangladesh is surrounded by several highly seismically active regions and has long experienced earthquakes and tremors. However, in 1954, the Bangladeshi meteorological department installed a seismic observatory in Chittagong and since then there apparently have been strong evidentiary indications that seismic activity in Bangladesh has increased over time. On the other hand, by all accounts, this seismic observatory is not only underfunded but is also not in full operation mode, which means that tons of seismic data is being lost.

So here is the nitty gritty:

Bangladesh is divided into three separate seismic zones a.k.a. Zones I, II, and III. Zone I is comprised of the Dauki Fault, the Sylhet Fault and is in close proximity to the Jaflong, Naga and Disang thrusts. Zone II is equated to the area spanning the uplifted Barind Pleistocene blocks and Madhupur Tracts, and the western extension of the Chittagong- Tripura folded belt. Zone III is basically the seismically dead zone in Southwestern Bangladesh and it experiences comparatively low seismic activity. So what does all of the former mean (seeing as that was essentially reorganized information taken from the sources I used)? Essentially, there is a lot of plate movement in Zones I & II, as you could probably guess from the words fault, fold, uplift & thrust. So here is a map of the three zones, if only for visual understanding.

If you happened to read my last post you will already be aware of my confusion regarding where Bangladesh is in a tectonic sense. I understood that it was part of the Indian subcontinent and bordered by the Australian subcontinent and that it is near the Indian continental boundary with Asia which is a massive and fast paced subduction zone, but there were articles describing the Burmese plate and several other factors which I could not seem to find any meaningful information on. Well, now I sort of get it. India (to the west of Bangladesh) is moving at approximately 7cm per year North, subducting beneath the Eurasian continent (which is located on the north and northeastern border of Bangladesh). On and including the far eastern side of Bangladesh is the Burmese plate which is moving southwest at a pace of about 2cm per year. Right, smack-dab above Bangladesh is the Himalayan Arc which causes seismic activity all the way over in Pakistan. The capital of Bangladesh is a city called Dhaka, and guess where it sits; right at the converging point of the Modhupur and Sylhet Assam faults. Dhaka is not only the oldest city, but it is also the fastest growing city in Bangladesh, which is a problem because as we all know, when a city grown rapidly it often throws out the building safety codes and uses cheaper materials in order to build enough housing fast enough.  Dhaka is a metropolis filled with less than quality high-rise skyscraping apartment complexes inhabited by thousands of people. My guess is that the next big earthquake, (anything over a 5.0 on the R-scale) will probably have pretty dire consequences. Chittagong and Sylhet, two other largely populated cities in Bangladesh are also located in highly area. The last few quakes (2009) which affected Dhaka did so only in an emotional sense, causing panic but no real physical damage or deaths. The potential for disastrous or even catastrophic seismic events is very high, although it does not seem to have come to full tilt just yet. Massive earthquakes with extremely high death tolls have been predicted in the recent past but so far Bangladesh has only experienced the delayed repercussions of bigger earthquakes located at a distance far enough to avoid calamity. What did all the sites and articles I used for this entry claim was being done to prevent harm to the people of Bangladesh? A warning system has been put in place but very little has been done to improve any city’s architecture.

Other Sources: I have put the links here because it should be easier for you to find the papers I was reading with them instead with a full MLA biblio.

https://www.academia.edu/318379/Earthquake_in_Bangladesh_A_natural_disaster_and_public_awareness

http://www.bpedia.org/S_0180.php

http://www.scribd.com/doc/6956055/Earthquake-in-Bangladesh#scribd

https://www.academia.edu/429823/Earthquakes_of_Dhaka

Continental Info Intro

Bangladesh fits right on the farthest eastern border of the Indian continental plate, right next to the plate boundary between the Indian Plate and Australian Plate. That boundary is a subduction zone (according to the map provided by earthguide link). More specifically it is a continent-continent subduction zone, the Indo-Australian subduction zone. The Indian and Australian continents used to be part of Gondwana which was located further south, where Antarctica is now. Gondwana was also comprised of New Zealand, modern Antarctica, Tasmania, New Guinea, and New Caledonia (that one I did not know about). When Gondwana broke apart, all its pieces began their drift to their current positions. India smashed into the Asian subcontinent, forming the Himalayan belt approximately 65 mya. The Australian plate drifted just behind the Indian plate and ended up colliding with it. One of the more interesting things which I learned in the preliminary research I did for this assignment was regarding the potential that these two plates may be breaking apart because the two plates are moving northward at two different rates. It is actually strangely difficult to find any meaningful science regarding the tectonic movement in this area because the interwebs are crammed with blogs such as my own instead of journals.  Also Bangladesh is shown on every map at a really obnoxious angle from which it is hard to ascertain if it is on the boundary of the Indo-Eurasian plate boundary or the Indo-Australian boundary. I digress. When Bangladesh experiences earthquakes they will often be sort of massive aftershocks from the Indian sub-continent continuing northward into the Asian continent. I have a USGS app on my phone which alerts me of earthquakes around the world. Sometimes Bangladesh pops up. Usually the quake is no bigger than a 4.0. Many of these quakes occur on the India-Bangladesh border. I do not think I have covered everything. As I noted before, there is a lot of information to wade through and I am trying to narrow it down to good sources. I may add more to this entry later.

http://en.wikipedia.org/wiki/Indo-Australian_Plate

http://certmapper.cr.usgs.gov/data/envision/index.html?widgets=geologymaps&mapservice=geology_bangladesh&xmin=87.51&xmax=92.95&ymin=19.96&ymax=27.47

Hu, Xiumian., et al., Late Cretaceous-Palaeogene Stratigraphic and  Basin Evolution in the Zhephere Mountains of Southern Tibet: implication for the timing of India-Asia Initial collision: Abstract. Basin Research, 2011. Print.

Najman, Yani., et al. Timing of India-Asia Collision Geological, Biostratigraphic, and Palaeomagnetic Constraints. Journal of Geophysical Research, VOL. 115, (2010). Print.

http://earthquake-report.com/2012/02/16/bangladesh-earthquake-list/

Also relevant to my citations, if anyone ever has the time to watch the BBC Earth Series (1998), it is really good and it is a good visual way to understand how the earth came to look the way it does now, geologically speaking.  I particularly enjoy episode 5, Roof of The World, although some of the specific information is a little outdated, it is a good documentary if you like geology.

Geological Resources in Bangladesh

Sources:

http://www.gsb.gov.bd/rve/index.php?option=com_content&view=article&id=9&Itemid=10

http://en.wikipedia.org/wiki/Natural_gas_in_Bangladesh

http://www.banglapedia.org/HT/R_0273.htm

                Mineral deposits of Bangladesh include:

-          Coal                                       - White Clay

-          Peat                                       - Glass Sand

-          Limestone                           - Hard Rock

-          Gravel Deposit                  - (Heavy) Mineral Sand

A good portion of these, such as Hard Rock were terms which were very vague to me, so I looked into hard rock and glass sand a little further.

It turns out that hardrock vs softrock can refer to the setting in which the geologist studying the deposits works. Hard rock in particular refers to a setting in which the geologist in question is studying igneous or metamorphic petrology. So basically (as far as I can tell) Bangladesh specializes in mining bedrock of an igneous or metamorphic origin, which it presumably uses to build foundations to a stronger infrastructure. Glass sand is essentially sand composed of silicas like quartz and feldspars and is therefore better suited to making glass. Heavy mineral sand is essentially sand made up of minerals such as Zircon, Magnetite and Rutile which may be found on coastal beaches (ancient or contemporary).

Apart from the aforementioned mineral deposits, Bangladesh has a pretty enormous natural gas output which makes sense given the fact that peat and shale are some of its major deposits. Apparently most of the vehicles driving around Bangladesh are fueled by gas rather than liquid fuel which had brought down carbon emissions in the country. Natural gas is definitely Bangladesh’s biggest natural resource. Gas is generally found in the Miocene and Pleistocene deposits between 1,000m and 3,500m beneath the surface in sandstone and shale deposits (reservoirs). These hydrocarbon reservoirs are essentially places where natural gas or oil migrates to and accumulates over time. It makes sense therefore that the reservoirs in Bangladesh are mostly found in sandstone deposits due to the fact that sandstone has high porosity- lots of space in between particles for the gas to reside in.  Most of these natural gas reservoirs or fields are found in the Indo-Burman ranges or rather, the eastern parts of the country, according to banglapedia.

The government owns all of the mineral rights in Bangladesh (a fact which popped up in almost every search I did).

The differences among hazards, disasters and catastrophes are pretty straight forward. Basically, a natural hazard is a natural process of the earth, like a volcano. Magma bubbles up at a plate boundary and BLAM you have a volcano which only gets labelled as a hazard depending on how it will affect humans. So if you build your village at the base of a mountain and it begins to ooze a slow basaltic lava flow which encroaches on your village borders, it simultaneously becomes known as both a volcano and a hazard. A natural hazard can become a disaster when it fulfills the following criteria:

- It kills ten or more people
- It affects or displaces 100 or more people
- International assistance is requested
- A state of emergency is declared

Furthermore, a disaster occurs over a limited period of time. A disaster may escalate to a catastrophe if an organization providing assistance does a heck of a job, causing more issues and making it more difficult for the civilization to recover. A catastrophe has all of the same criteria except that it usually occurs over an extended period of time. Years can pass before the aftermath of a catastrophe is rectified or the people affected recuperate. To recap:

Hazards: are natural occurrences on earth which become exacerbated and dangerous when humans get too close.
Disasters: Hazards which severely affect nearby humans for a short period of time and which can often cause death and general mayhem.
Catastrophes: HUGE disasters which not only cause numerous deaths and structural damage in the onset but which also take for-ever to recover from and often continue to cause death and mayhem for years after the initial event.