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Half 4 of a collection on monitoring panorama modifications in Bangladesh. Learn half 1, half 2 and half 3 right here.
Having completed the servicing and repairing of devices within the coastal zone to take a look at land subsidence and sedimentation, the remainder of my fieldwork focuses on the GNSS (the final time period for GPS) devices in japanese Bangladesh to check the tectonics and earthquake hazard. The day after we returned to Dhaka, Austin left to return residence. The next day Lin Shen, my postdoc, and Ken Austin, a geodetic engineer, arrived. Lin is utilizing satellite tv for pc radar information to picture the land deformation within the IndoBurma subduction zone. This can be a likelihood for her to see the realm up shut and private. Ken is from the EarthScope Consortium, previously UNAVCO, which is funded by NSF to help geodetic analysis. I’ve been speaking to Ken quite a bit over the previous few weeks as he helped me get the GNSS receivers within the south again on-line. That is the primary time that I’ve met him in individual.
After I spent a few days in Dhaka, the capital, in additional conferences, we met Sanju Singha, who has been caring for the devices at Dhaka College, to pack up all of the tools that we are going to want. Sanju is staying behind for some job-related examinations, however will be a part of us in one other day. Lin, Ken, Babu and I drove east throughout the Meghna River to Comilla, close to the border with India.
On the best way, we stopped at Mainamati, the big ruins of a 1,200 yr previous Buddhist monastery. On the Friday afternoon earlier than Ramadan, it was crowded with guests and college journeys. Combating the group, I managed to order the tickets in Bangla. As soon as inside, we grew to become celebrities, with scores of individuals taking selfies with us. After we left at closing time, we continued to our lodge. Since we had a big late lunch on the best way, we skipped dinner and crashed for the night time.
When one lithospheric plate subducts beneath one other, the 2 plates stick to one another. The higher plate will get deformed till the stress turns into too excessive, after which it jumps again in an earthquake. Since right here the 2 plates are converging at ~12 mm or lower than half an inch per yr, it will possibly take a very long time earlier than it reaches the breaking level. Nevertheless, we don’t know the way lengthy or when the final earthquake right here was, so we are able to’t inform when a big earthquake would possibly occur, days or centuries. All we all know is that we are able to see the locations deforming with our GNSS. We can be visiting seven websites over the subsequent week, all in want of restore or reinstallation to higher outline the plate movement and the way the plates are deforming. Our devices can measure positions to ~2 mm within the horizontal and 6 mm within the vertical. That signifies that after years of observations, we are able to detect motions of 1 mm/yr or higher, which nonetheless amazes me.
Our first place to go to is Raipur, about 2.5 hours to the SW. We had a station right here from 2007-2016 in a authorities visitor home, however needed to return the loaned receiver to UNAVCO. Since every little thing is gone however the antenna on the roof, we arrange the tools field and photo voltaic panel on the roof. After we bought as much as the roof, we noticed that timber on each facet had grown and blocked the view of the sky. Whereas a sign nonetheless got here via, we anxious about multipath—the radar sign from the GNSS satellites—bouncing off the timber. I checked out my present processed information and will see the scatter of the information enhance via time till on the finish of my information it grew to become very dangerous. That is not a superb website. Nevertheless, since it’s over seven years since we acquired information from right here, even noisy information will present some further constraints. For some time. We talked over whether or not to put in right here, however with no new website scouted and it being a weekend, and never having every little thing we’d like for a brand new website, we determined to go forward and reinstall it. I’ll effectively transfer the tools to a brand new website in a yr or two.
Lin and I put in the photo voltaic panel, whereas Ken arrange the tools field. After getting every little thing in place, the modem proved to be very temperamental. Ken alternated between attempting two completely different ones, however ultimately bought it to work. In the meantime, Babu and I went out in search of locks to safe the field and bolts to chain it to the roof. After cruising round, we lastly discovered what we would have liked. By the point we had been accomplished it was nearly 7:30pm. We didn’t get again till after 10 pm, glad that we had had a big late lunch. We had gentle snacks for dinner and Sanju arrived whereas we had been consuming.
Subsequent was a website at Comilla College, located on prime of the primary anticline, or hill, product of the delta sediments which were folded up by the subduction zone. It’s only 30 meters (100 toes) excessive. Those we are going to go to tonight in Sylhet are a lot bigger. The hills in Sylhet are the place a lot of the tea in Bangladesh is grown.
We collected information from this website for 4 years, from 2012-2016, till the funding ended. After the mandatory greetings and cups of tea, we went to the roof. This website is plugged into the grid with a backup battery for energy outages. The battery was gone and the ability converter damaged, the cables nearly chewed via by the rat that scurried away after we entered, however amazingly the receiver was nonetheless working with over 4 years of information saved on it. I’m thrilled. We tried to repair the ability converter, however couldn’t. As an alternative, we are going to arrange a photo voltaic panel just like the websites we are going to go to later. This website additionally took longer than I imagined, so we lastly reached our lodge in Sylhet, probably the most northeastern a part of Bangladesh at midnight.
For the remainder of the fieldwork, we’re staying exterior of Srimongal, the tea capital of Bangladesh on the Tea Resort and Museum. We’ve a three-bedroom cabin on the spacious grounds with a tea backyard behind it. Because the Muslim holy month of Ramadan is beginning quickly, we’re the one company. We’ve 5 websites to service in 4 days, none greater than a two-hour drive away. Southern Sylhet has a collection of north-south hills the place the delta sediments are folded and thrusted by the subduction zone. The flanks of the hills are coated in tea plantations. Our GNSS stations span the hills to measure how briskly the land is being compressed by the subduction zone, constructing stress in direction of a doable main earthquake.
With the final two lengthy days, we determined to do what we hope would be the best website first. We slept in then went to the Ichachara main college (ICPS), an hour and a half farther east. We downloaded the information, modified the batteries, and as soon as once more struggled with getting the modem related. Nonetheless, we had been ready to complete every little thing by 3pm, together with taking photos with the lecturers. Nevertheless, we didn’t discover a good restaurant till we drove all the best way to Srimongal, so lunch was as soon as once more at 5pm. This gave us a night to loosen up in the lounge collectively. Solely Sanju and Babu went out for a dinner as Babu begins his Ramadan quick tomorrow. The remainder us, nonetheless fairly full from the late lunch, simply snacked on chanuchur, roasted soybeans and protein bars.
For our subsequent day, we headed to JURI, our farthest station in a medical clinic. Right here the battery was fully useless. We modified it and the solar energy controller. As ordinary, issues arose with the modem. This journey, it appears, the issue is all the time the modem. Ultimately, Ken bought the modem software program upgraded and dealing. As soon as once more at this website, timber are obscuring the sky view and we organized to have a few of them reduce.
Afterwards, we visited Arman, who I labored with on two electromagnetic surveys in 2022, at his area workplace in Juri City. He’s working for BAPEX, the Bangladesh Petroleum Exploration firm, serving to to gather a 3D seismic survey within the space. Sanju and Babu know numerous his colleagues, so it was a little bit of a reunion for them. We stayed till after sundown when everybody was capable of break their Ramadan quick, then headed again for our dinner and a few relaxation.
Now it was time to attempt two stations in the identical day. It was an hour drive throughout the hills and a rice-filled valley to SSPS at one other main college. Right here the receiver field was contained in the headmaster’s workplace, because it was beforehand damaged into on the roof. Lin helped change the batteries and Ken labored on upgrading the modem. I joined Sanju to take care of the scenario on the roof. The college had put in a water tank proper subsequent to the antenna blocking out half the sky. The college agreed to maneuver it. Sanju and the individual transferring it went up the ladder to the roof. As I adopted, Sanju warned me to watch out that the ladder was weak. On my subsequent step, the ladder broke in half sending me tumbling. I bought a bit banged up, however fortunately no severe accidents. The heel I landed on continues to be sore, and I banged up my hip and elbow, however I’m recovering. After that, I watched from under as they relocated the water tank.
After three hours we had been accomplished and moved on to DCPS, a main college on the identical anticline (hill) as our lodge. As solely Babu was fasting, the remainder of ate our packed lunch on the college, which has a sturdy iron ladder. Then we went to work, altering rusted cables, the batteries, and so on. Since it’s only 10 minutes from the place we’re staying, Ken determined to take the modem again with us and return within the morning. After hours of labor, together with working with Jim Normandeau again at UNAVCO, the modem nonetheless wouldn’t take the upgrades it wanted or acknowledge the SIM card. Ultimately, Ken had to surrender. No must cease again right here within the morning with no working modem. After he returns residence, Ken will configure a number of new modems for me to get to Bangladesh and Sanju will swap them in.
Our final cease was in Chanurughat (CHNR), a city in the course of the flat valley between the hills. It’s a school (high-school stage within the US). The tools field is in a primary ground room. After we opened it, the receiver was working however confirmed no satellites being recorded. We couldn’t get it to see the satellites. We tried a spare receiver we introduced and that didn’t work. We went as much as the roof and after we eliminated the antenna, we discovered it was cracked and crammed with water. It’s now a memento. After we changed it with a spare, every little thing labored, besides the modem, in fact. Put in in 2012, the mannequin was too previous to run the present VPN used to obtain information, and none of our remaining modems had been working. We concluded with a picnic lunch in a tea backyard close by.
We had now completed all of the GNSS work. All 16 stations had been now recording information. Twelve of them are on-line and sending the information again to the States. Two websites unused since 2016 had been resurrected as a part of the journey. We collected loads of information from the websites that had been nonetheless operating. We celebrated the top of the fieldwork with inexperienced coconuts and a ultimate dinner out. This effort throughout Bangladesh will assist us perceive each the earthquake hazard within the east, and land subsidence within the south. The RSETs measuring elevation change, sedimentation and shallow subsidence had one of many twice yearly measurements. We collected ~230 sediment samples from many websites from as much as 19 toes under the floor to assist us perceive the causes of the subsidence. This was a protracted journey with 12 folks contributing, together with the 2 drivers. Plus, there was the crew of the M/B Bawali. We drove the 4.5 hours again to Dhaka and Lin and Ken flew residence within the night. I stayed one additional day for but extra conferences after which adopted.
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