After a 45-minute delay, the plane arrived at Nakhon Sithammarat Airport. This is my second visit to this airport. It is located in the south, but it was cooler than Bangkok. It was almost 9 o'clock at night.

Mr. Focus, a physics teacher at PCSHSNST, who will take care me this vist. He picked me up at the airport late at night.  His nickname is like a physics teacher, but he also took geophysics classes at the university. Thank you very much for your help last time and this time.

As in our previous visit, we are staying at a very nice 4-star hotel and will start with a sumptuous breakfast.

The view from the hotel window. Colorful apartments. Although still within the city area, the city is still in the process of development. There is a large BiG-C at the end of the road on the left side of the street.

Fruits we had for lunch. Citrus fruits like large Japanese Hassaku(Pomelo) are a specialty of this area. They are sweet and delicious. We had a lot of them at the last visit.

First, the seismograph was repaired. As expected, the pendulum is bent by the weight of the horizontal pendulum. The first thing to do is to adjust it to moving upward the magnetic circuit.

But one of the pendulums was in a very serious condition, and the underside of the pendulum was hitting the pillar. I didn't have a file, so I had the school van take me to a nearby HomePro (a big DIY shop) and bought a file and other tools. I shaved the bottom part of the pendulum so that it would not hit the pillar.

However, the cause was a broken thin phosphor bronze spring at the fulcrum. After finding the cause, the leaf spring was replaced, and the final assembly was done by students who were watching. It is my educational policy to have students do as much of the work as possible, and not have the teachers do too much.

As expected, the main spring was worn out after two years of use. Using a plier I bought at HomePro, I cut it a little shorter to increase the spring tension and reassembled it. Both the cutting and the installation of the spring were a bit dangerous, so I did them myself and let the students watch. However, since the students are in their first year of high school, they are expected to help with maintenance from now on, so I asked them to observe all the work.

The three seismometers have been repaired and the installation is complete. The direction was checked and the north-south axis was adjusted. The phases of the pendulums were also checked. The amplifiers have also been slightly leveled and are now almost complete.

In addition, a data folder is shared on the PC so that data can be automatically uploaded to Google Drive via wifi. This allows me to check the data in near real time from Japan. However, the network sometimes stops due to the construction of a new school building in the neighborhood, but that can't be helped. Thanks to Focus Sensei of physics department and M4 student who helped me with the assembly.

The special class for the students was a magnitude measurement using waveform data from the Japan Meteorological Agency (JMA). This is a teaching material created by my research grant 15 years ago. The textbook is written in English for overseas users. The nomograms can be used to easily obtain answers without complicated logarithmic calculations.

Here is another day's observation of a thin-sections using a microscope and my home-made polarizing unit. Naturally, the students took pictures with their smartphones or tablets and sketched while looking at the pictures. These six students are first-year geography majors under the guidance of Focus Sensei. Their interest in and understanding of geology were very good. They also participated in the field trip the next day.

This is a very beautiful sketch. The sketch shows thin-sections of granite and peridotite. The granite is Mannari granite in Japan, and the peridotite is from Horoman, Japan and the xenolith from Chanthaburi, Thailand. Other sections shown were gabbros from Cape Muroto and Cape Shionomisaki, and pyroxene andesite from Kagoshima, Japan. The gabbro of the Cape Shiomisaki shows beautiful euhedral olivines, so I asked the students to think about the order of crystallization from the magma.

This microscope is used for observation. A home-made polarization unit is mounted on the stage. Please refer to the following web for the construction of this unit.
http://seagull.stars.ne.jp/2018_Gadget/Polarized_Microscope/index4.html

This is an example of a student's sketch. The student was able to distinguish the minerals. It is a very good sketch done in a short time. We are currently collecting class questionnaires and will report back when we have collected them.

On the last day of our stay, we are going on a field trip. The school van will pick us up and take us to the mountains northeast of the city, where the GPS shows low, tropical latitude.

The office building of the national park. Click on the picture for a video.

The tour road of visiting seven waterfalls in the mountains of Kaorwan National Park. The tour was a little less than 4 km long and visit only two major falls, but there were some steep slopes, and the accompanying teacher seemed to be having a hard time. On the way, a guide from the national park explained about plants and other information. Two geology professors from a local university also accompanied us and explained the geology.

This is the smaller of the two waterfalls, but it is still over 10 meters high, and the sheer volume of water is overwhelming, especially after the monsoon season (December). The geological formation was difficult to interpret. The explanatory pamphlet in Thai that we were given said only Paleozoic sandstone and shale formations (translated by a smartphone camera, it said Cambrian). As I discussed with our professor, it was a difficult place to interpret. In my opinion, the sandstone and shale are a little weakly metamorphosed.

In fact, there was something very interesting in the mountains leading up to the waterfall. This area is where the communists holed up in the mountains from the 1970s to the 1980s for military training, partly due to the Vietnam War. This is a signboard of a limestone cave that was used by the Guerrillas as a basketball court. In addition, there is an another sign showing the human made pitfalls for solders that were common during the Vietnam War.

This is the main Krungchin Waterfall. I searched for information in Japanese, but could find very little. It may be that they intentionally do not include it in tourism to avoid environmental destruction. It falls in two stages, and the total drop reaches about 100 meters, but there is not much information available, so I will look for more details in the future. This waterfall also has a large volume of water, and I think it is one of the best waterfalls I have seen in Thailand. The geology of this waterfall is a beautifully sloped sandstone shale layer on the right side of the waterfall. The pamphlet explains that the strata is mainly shale, and the stepped part is sandstone that is highly resistant to erosion. Again, It seems to me that the rocks have a very advanced diagenesis appearance.