International Joint Workshop on
Slow-to-Fast Earthquakes 2024

Updated on August 27, 2024

Post-meeting Field Trip (September. 20-21)

Fossils of Slow and Fast Earthquakes in Subduction Zones: Makimine Mélange and Nobeoka Thrust in the Shimanto Accretionary Complex

沈み込み帯のSlow地震・Fast地震記録：四万十帯槇峰メランジュと延岡衝上断層

Field Trip Overview

A two-day geological field trip to the Shimanto Belt will be conducted after the plenary session. The Shimanto Belt in southwest Japan is an accretionary complex formed by the subduction of a young oceanic plate and is thought to record deformation similar to that at depth in the Nankai subduction zone. At the Makimine mélange, we observe quartz veins that are thought to record Episodic Tremor and Slip at the subduction plate boundary. At the Nobeoka thrust, we will observe the internal structure of a megasplay fault in a subduction zone.

Field Trip Highlights:

1.     At Nomi (Stop 1), quartz veins in the Makimine mélange, possibly recording the episodic tremor and slip (ETS) along subduction plate interface, will be observed.

2.   At Shimoaso (Stop 2), cleavage overprinting the bedding of sedimentary rock will be observed.

3.   At Tomi (Stop 3), the large scale shear zone of the Nobeoka thrust, including thrust deformations under fluctuating fluid pressure as well as pseudotachylyte along a subsidiary fault, will be observed.

Important Details:

• Meeting Point: 9:00 AM, September 20 (Friday) , at the bus terminal near JR Beppu Station.

• Conclusion: The following three locations will be used for the break-up of September 21 (Saturday): 1) after 13:30 at JR Nobeoka Station, 2) after 16:00 at Oita Airport (by buss), 3) after 16:00 at JR Beppu Station (by car).

• Capacity: Maximum of 40 participants (selection may be necessary).

• Participation Fee: Free (meals & accommodation expenses are not included).

• Accommodation: Single room will be arranged by organizers, paid by each participant

• Guides: Asuka Yamaguchi (AORI, UTokyo), Makoto Otsubo (AIST) and Kohtaro Ujiie (Univ. Tsukuba)

• Field Gear: At Stop 3, you will walk along the rocky coastline for about one hour from the bus stop to the outcrop. Long sleeves, long pants, and trekking shoes are required.

• In case of heavy rain in Sep. 21, we will visit Takachiho (welded tuffs erupted during the caldera formation of the Aso volcano and steep canyon) instead of the Stop 3.

Itinerary:

Sep. 20

• 9:00: Meet at JR Beppu Station.

• 11:00-13:00: Stop 1 (Nomi) Makimine mélange, with lunchbox.

• 14:00-15:45: Stop 2 (Shimoaso) Kitagawa group.

• 16:30 arrive at hotels in Nobeoka City.

• Group dinner

Sep. 21

• 8:30: leave the hotel.

• 9:00-12:30: Stop 3 (Tomi) Nobeoka thrust, with lunchbox.

• Approx. 13:30: Breakup 1) at JR Nobeoka Station.

• Approx. 16:00: Breakup 2) at Oita Airport.

• Approx. 16:00: Breakup 3) at JR Beppu Station.