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The 2019 Group of SHA (G-SHA) workshop was held in Toyako from November 4 to 8, 2019. The opening ceremony speech entitled "The 10 Years G-SHA Workshops" addressed the G-SHA activity history. The G-SHA workshop initiated by China-Japan-Korea strategic program after the 2008 Wenchuan earthquake, inherited by Japan (NIED) and Taiwan (TEM) from 2012, as well as New Zealand (GNS Science) from 2014. G-SHA summit holds the annual meeting in turn in the member's countries and became only one international Probabilistic SHA workshop in the world.

About 84 people joined the workshop and/or field-trip, 28 participants from Taiwan, 7 from New Zealand, as well as 44 participants from Japan. We also invited the national PSHA team’s leaders from USGS, GEM, Singapore and Korea. The 24 Oral presentations including 3 invited and the 26 poster presentations were delivered from issues as below:

• Current status of Seismic Hazard Assessment for each country
• The 2018 Hokkaido Eastern Iburi earthquake
• Active faults and Paleoseismology
• Seismic hazard and risk
• Deformation, fault displacement
• Earthquake and Ground motion

Please see the Abstract Proceedings for the details.

We glad noticed that both of oral and poster presentations attracted much attention, especially for the young researchers. Some of them excited that a new research theme inspired, and the team formed to work with. The group discussions became conventional events after the 2015 G-SHA workshops. Five groups as shown in photos, formed twice by individual interests, discussed comprehensive themes, dilemmas, future researches they’re faced. The final wrap-up presentation carried out around the huge oval table in the G8 summit memorial, Toyako. The group leaders as listed below delivered each group’s summary.

G1: PSHA and model validation

Group leaders: Chung-Han Chan and Matt Gerstenberger

G1 wrapped smoothing model, decluster catalogue, multiple-fault rupture, segmentations, and more than 11 issues. G1 proposed PSHA questions-orientated workshop focus sessions as the 2015 NIED-TEM practice workshop. All of participants highly emphasized and appreciated the PSHA issues in the G-SHA workshops.

G2: Ground motion prediction and site amplification

Group leaders: Hongjun Si and Nobuyuki Morikawa

G2 focused how to module and validate 3D underground velocity structures, and how to validate ground motion models.

G3: Scenarios and subduction zone modeling

Group leaders: Bill Fry, Yin-Tung Yen and Yen-Yu Lin

G3 put 4 top priority problems of Fault interaction, Mmax, Shallow processes and Near-field problem.

G4: Hazard and risk products

Group leaders: Toshihiro Yamada and Elizabeth Abbott

G4 raised questions such as, what products do we need in order to fill the needs of our stakeholders? How do we best engage with the people who need the outputs to ensure usability? Though this may vary from country to country, what hazard/risk information can we provide to better respond to and educate end-users? How does this message vary between different end-users? What do the needs of end users mean for evolution and development of the models themselves?

G5: Fault structure and deformation model

Group leaders: Takashi Azuma and Andy Nicol

G5 discussed fault source model; fault geometries; fault parameters and the uncertainties of fault models.

After the meeting, about 48 people joined the field trip following the order of volcano disasters, active fault investigation, and 2018 Iburi earthquake landslide disaster. Please see the fieldtrip guide book for the details.

Volcano disasters of Showa-Sinzan, Usu volcano and the 2000 eruptions, gave much impression of many professionals who has first-time experience. Then, we visited Kuromatsunai for active faults where the highest occurrence probability 2-5 % for next 30 years in Hokkaido. The 8 people from Tokyo university of Science joined the active fault investigation. Local Hokkaido Newspaper reported the workshop and field trip activity. Finally, we visited the huge landslide areas at Horonai and Sakuraoka before departure.