Finally back to bangladesh
Some bright green tea trees growing on the slopes of Sylhet, the tea capital of Bangladesh.
Due to the COVID-19 pandemic, it has been almost two years since I last time in Bangladesh. During this period, all the GNSS (GPS) receivers we set up for two different projects in 2018 and 2019 stopped working. Therefore, with the help of Sanju Singha, a graduate of Dhaka University, I will stay here for three and a half weeks to visit and repair them. He has been criticizing me for maintaining the station.
Opening the equipment box, I can now see with my own eyes how everything in the battery acid mist is corroded.
The first stage of this trip was to visit our 5 stations in Sylhet, northeast Bangladesh. This is the area where the delta sediments are folded by the Indo-Burma subduction zone. The folds form hills with forested tops. The flanks are used for tea gardens, usually called tea gardens. The valley in the middle is covered by rice fields. Below the fold is a nearly horizontal subduction giant thrust fault, which is a fault that may rupture in a major earthquake. For many years, our GNSS station can measure ground motion at a speed of 1 mm/year or better to better understand fault motion.
The charging station in Sylhet malfunctioned due to the leakage of battery fluid from the first set of batteries we used. Sanju is able to replace the battery with a better battery, and clean the equipment box as much as possible and replace some of the internal parts. I brought a bunch of replacement parts: solar panel controllers, modems, cables, wiring blocks. Most of the equipment is provided by UNAVCO, a consortium that assists American universities in geodetic surveys.
The colorful elementary school hosting the ICPS now has a dramatic pond dug in front of it.
Sanju and I left the capital Dhaka on the 29thday Together with Babu in December, he has been our driver since 2005. On the way to Srimangal where we will stay, we stopped at the first stop of Chunarughat (CHNR). It is located in the middle of the valley of a university. Now I want to see how bad things are in the equipment box. The waterproof box contains all the leaked liquid inside, and the acid mist corrodes everything.
In Bangladesh, we often need to use interesting ladders to reach the roof. Here, Sanju stands on a single pole ladder.
The wood is almost black, the exposed connectors are all green, and so are the ends of the copper wires. Corrosion means that the solar panels cannot provide power, and the batteries are exhausted and damaged. We even found that the SIM card in the modem has been corroded and must be replaced together with the modem. We spent several hours cleaning and replacing everything. Surprisingly, even though unused connectors are corroded, expensive GNSS receivers can still work normally. UNAVCO is able to remotely program the new modem. The station has now been restarted and running. success! We went to Srimongal and picked up Shofiqul Islam from a university in Sylhet at the train station. In 2021, Shofique spent 7 months in Lamont, folding and pushing on the hills of Bangladesh with me.
After finishing the first stop of the day, we stopped to enjoy a quick lunch of freshly made Singara (samosa) fried in a pan and Mughlai (rectangular dough with eggs and vegetables) being prepared.
The next day, we drove east to the two furthest stations. ICPS is located on the roof of an elementary school, on the side of a hill in a remote area reached by driving on poor roads. The road is hardly wider than our van, so overtaking other vehicles is always a challenge. This time, we can get the receiver to work, but the key cable to connect the receiver to the modem is missing. If there is no substitute, we have to leave it without data transmission. However, it is recording data internally. When I travel next time, I will bring the necessary parts and Sanju will complete the repair.
In this culvert, we have to use bricks on the road so that the van can pass through it.
We took a shortcut to JURI Station on the other side of the mountain. We did not bypass the hills, but through the tea plantations and ecological parks. This station is in a medical clinic. They want us to move the receiver out of the delivery room, but this must be done on another trip. This time the modem was normal. After repair, JURI went online again. The problem with the station was that the trees growing around the clinic blocked the aerial view of the sky. This station had this problem before. The betel nut partially blocked the view from the north, but the worst thing was that the branches of a tree were above the antenna. Sanju will have to discuss cutting down or at least pruning trees with the director of the clinic next week. Looking at the previous data from this site, I can see that the most recent data is about 3 times less accurate than the old data.
Drinking tea and biscuits at the homes of Adu Salam (left), Sanju (middle) and Babu (right)
The fourth station, SSPS, was also in elementary school, was vandalized and stolen the battery. The damaged box is no longer waterproof, and rain damaged the receiver. However, the sixth site had to be demolished because they expanded the school where it was located and added a new floor to install our antenna. We installed a KGPS receiver instead of SSPS, but relocated the box in a safe storage room inside the school. This makes the work longer. To be safe, we had to reinstall the solar panels and add grounding arresters to the antenna cables before we could enter the school. Nevertheless, we completed the train to Sylhet back to Sylhet in time. The SSPS site is in a beautiful location, but it is difficult to reach. The concrete culvert on the creek stood above the dirt road, which made it difficult for the van to drive over. We had to go out several times to reduce the weight of the truck. At one location, we built a brick road so that the truck could drive past. It worked, we could drive to the scene instead of having the battery and equipment in the last 1/2 mile. After the end, we drank tea and biscuits in the mud-bamboo house of the head of the school council, and some hard-boiled eggs ordered by Sanju from a nearby store. Then on New Year’s Eve, we stopped for an afternoon snack at an upscale resort with our own tea garden, and then drank tea in a local tea house. The contrast between styles and prices is amazing.
We celebrated New Year’s Eve by stopping for a walk and enjoying snacks in the beautiful resort.
Our last stop was also a school. It is located on the top of the mountain closest to Sri Mongar, the Chadus of Bangladesh. Repairs are similar, except that the confusion of solar panels took our time. We are now on the way back to Dhaka. When we were there, school children came to buy new books for New Year’s Day. We have repaired all 5 GNSS stations and restored remote data transmission for three of them. In general, this is the first stage of my trip very successful. Now I will spend the climax in Dhaka next week, and finally attend the Bangladesh wedding, and then travel south by car and boat to visit 9 other stations.
I was surprised to see children and parents at school on New Year’s Day. Here, all children will get new books to celebrate the New Year.
Data from these stations can help refine our estimates of the incidence of subduction. They were used by Lamont graduate student Bar Oryan as part of his thesis. The longer the time series of data from GNSS stations, the more accurate the estimate of the dive rate and overall structure. The results have shown that this speed is slower than my previous estimate, which is expected to mean longer time between potentially catastrophic earthquakes.
