3:45 PM - 4:00 PM
[MIS08-02] Example of Study of the Itoigawa-Shizuoka Tectonic Line using “NIED Quake map!”
Keywords:Itoigawa Geopark, Fossa Magna Park, Itoigawa-Shizuoka Tectonic Line, NIED Quake map!
The Itoigawa Geopark in Niigata Prefecture features an educational park centered on a fault exposure of the Itoigawa-Shizuoka Tectonic Line (ISTL) called the Fossa Magna Park which was first opened in 1990. It is a roughly 10 minute walk from the main parking lots along National Route 148 to the fault exposure. One of the interpretive panels near the exposure features a QR code inviting visitors to examine the 'NIED Quake map!', a page which records seismic activity managed by the National Research Institute for Earth Science and Disaster Resilience (NIED). This report presents one example of academic study using the 'NIED Quake map' with high school students.
2. Earthquake and Fault Study Example (Private High School in Kanagawa Prefecture)
(1) Explanation of the Fossa Magna and Earthquakes (Via Outdoor Interpretive Panels)
The students learn that the ISTL forms the western fault boundary of the Fossa Magna, that has a very close connection to the formation of the Japanese Archipelago, and that the movement of faults causes earthquakes and particularly large fault movements cause the faults to reach the surface where they are called active faults, and that these movements over time form and shape the land around us.
(2) Information from 'Quake map!'
The students use their own smartphones to access the 'NIED Quake map!' site where they can observe the earthquake activity for past ten years in the Itoigawa Area. Through this the students understand the following:
There are many earthquakes occurring around us, even if we don't feel them.
There are distinct areas where earthquakes do and don't occur.
There are earthquakes which concentrate in a line or elliptical shape.
Inland earthquakes occur at depths shallower than 10 km.
There are earthquakes which occur both along and away from active faults.
Along the same active fault, there are areas that do and do not have earthquakes.
Itoigawa experiences no historically large earthquakes, so there is no active fault.
Areas which experienced historic earthquakes have a greater concentration of earthquakes.
Afterwards, the students look at the 5 year, 1 year, 30 day, weekly and 24 hour maps. On the 24 hour map they can see recent earthquakes, where many students are surprised by how many earthquakes occur without being felt.
(3) Fault Exposure
The students see that the fault exposure is crumbling and the rocks have been broken. The gaps among the fault breccia are filled with even more broken fine material (fault gouge) which can be easily depressed with a finger. In fault gouge, striations which show the direction of fault movement can be observed, so the students can understand how fault gouge was formed by the crushing of rock by fault movement. An earthquake of magnitude 7 causes a change in elevation of about 1.5 to 2 m, so the gap seen along the ISTL (over 6,000 m) can be understood to have formed over 3000-4000 fault movements. Through this the students can imagine how deep the Fossa Magna is. They can also understand how faults expand.
The earthquake distribution map of 'NIED Quake map!' allows for visual understanding of Japan's most tectonically active places and is a valuable tool for understanding the connection between earthquakes and faults. Studying the fault exposure allows seeing only the result of geological processes, but using 'Quake map', the students get a better image of these processes and how they are continuing beneath us. Hopefully further experience in using 'Quake map' for high school students can be used to improve its use in earthquake risk reduction education.