Search

Based on solid evidence, scientists attribute the global warming trend observed since the mid-twentieth century to the human expansion of the “greenhouse effect.” Extreme rainfall events have become more frequent worldwide, resulting in hydro-meteorological hazards creating more deaths and devastation. One of the most remarkable disasters of rain-induced rapid long-traveling landslides (RRLL) in Sri Lanka took place at Aranayake, 70 km east of Colombo, in 2016 (JICA Survey Team (2016), Survey results of Aranayake Disaster, JICA. URL: https://www.jica.go.jp/srilanka/english/office/topics/c8h0vm00006ufwhl-att/160720.pdf [Last accessed: April 14, 2020]). The fluidized landslide mass ran over an about 2 km distance claiming the lives of 125 people. This tragic event highlighted the importance of reliable early warning and disaster management mechanisms even more than ever because the presence of these hidden unstable soil masses, as well as their run-out distances, are hardly predicted. Once they start sliding, it is almost impossible to stop them. Since 2020 (after the preceding period of 2019), both the National Building Research Organization, Sri Lanka (NBRO) and the International Consortium on Landslides (ICL) have jointly started a new 5-year research project, “Development of early warning technology of Rain-induced Rapid and Long-travelling Landslides (Project RRLL),” within the framework of SATREPS. SATREPS, standing for “Science and Technology Research Partnership for Sustainable Development,” is a Japanese government program promoting international joint research. This article reports on the outline of the project, including its background, goals, plans of plots for developing critical technologies for the early warning system, etc.

In seismically active regions, loose saturated sandy soils are prone to liquefaction. A strong ground shake can create considerable excess pore water pressures in these soils and temporarily decreases the effective stress and shear strength, leading to strength loss, excessive ground settlements, and lateral spreading. Not to mention the immediate ground deformation, post-seismic settlement, and lateral ground spreading often build up slowly and steadily, causing problems for quick rehabilitations to lifeline facilities, etc. However, this long-lasting post-quake deformation buildup has caught less public attention, and quantitative pieces of evidence are less numerous than those about immediate impacts. This article reviews case histories, showing quantitatively that liquefied soils can remain soft for months.

The impact of a large inland earthquake is profound because of its intense shakes and the associated landslides and debris flows. The quake-induced landslides and debris flow are often the most devastating secondary effect of an earthquake in terms of all kinds of losses, causing long-lasting problems in post-quake rehabilitation activities. An earthquake-induced landslide is just one scene of ever-evolving mountain topography. Therefore, studying terrain dynamics is vital to comprehend the possibility of hazards and propose and apply rational rehabilitation tactics. Though serious, the damage caused by the Mid-Niigata Prefecture Earthquake of October 23, 2004, has given us a rare opportunity to study the landform changes caused by an earthquake that hit an active-folding mountainous terrain. To deal with rehabilitation problems in a scientific manner, a research program, “Earthquake damage in active-folding areas: the creation of a comprehensive data archive and suggestions for its application to remedial measures for civil-infrastructure systems,” was set up getting the Special Coordination Funds for Promoting Science and Technology, Ministry of Education, Culture, Sports, Science and Technology (MEXT). This article reviews some significant findings obtained through this project and even beyond it. The results show that essential aspects of quake-caused problems were linked to deep-seated tectonic displacements, namely the internal driving stress field associated with earthquakes to evolve the active-folding terrain.