Chihshang fault

It lies within the active major collision zone between the Philippine Sea and Eurasian plates.

An indentation low lying rift valley with two high mountain range aside, allows sediments and nutrients flow in with water from rain or streams.

In late Miocene age where sea level is high, flysch-like Plio-Quaternary sediments deposited forming layered sedimentary rocks.

Due to the compressional force generated by plate movements, the Hai’an Range rock layers experience folding, thrusting and uplift.

[citation needed] The East Rift Valley is formed from a group of Quanternary continental deposits.

The terraces form both the flat, low-lying East Rift Valley and the bumpy Hai’an fold mountain.

[citation needed] The Lichi Mélange between the Hai’an Range and the East Rift Valley is being a mean of separation.

The first three was the largest scale, magnitude greater than 7, and they took place at the northern tip of the valley which is where the city Hualien was located.

This is a historical earthquake in Hualien that made people pay greater attention to the tectonic activities here.

Part of the back side of the field ground was removed which displacement of rock layers was exposed and observed.

[17] Creaks on roads, infrastructures, buildings, and walls have appeared all along the East Rift Valley fault zone.

During fault creep and rock displace, the distance of two ends of rod-type creepmeter also change associatively, resulting in different data output.

[10] Two aligned creepmeters were placed across the fault behind the slide in the opened field ground of Tapo Primary school.

Thus, the rainfall pattern is an important factor which significantly affects fault creep movements.

Ground penetrating radar is a good method for tracking the temporal change for the structure of the fault.

But the ground penetrating radar cable can only image to a depth of 5 meters, seismic reflection lines are frequently used to obtain more data from deeper area.

High resolution seismic reflection technology of the type used can penetrate up to a depth of 60 - 300 meter.

Automatic soil radon monitoring stations were set up at fault zones where rod-type creep meter already exists.

While a lot of fault trace can be found in site own by villagers or under buildings, the source of investigation is restricted and reduced.