Until recently, scientists were puzzled why an earthquake of only 7.5 magnitude caused a devastating tsunami that killed over 2,000 people on the island of Sulawesi in Indonesia in September of 2018. The earthquake didn’t even trigger the tsunami early warning system as normally a tsunami of the size (wave height up to 11m or 36 ft) would require an 8.4 or higher magnitude earthquake. A new study published in the journal Pure and Applied Geophysics has found that the cause of the tsunami was actually a marine landslide in Palu Bay on the west coast of Sulawesi. A combination of computer modeling and observation of the actual sea level data from the event was used to reach their conclusion. They observed a wave period that was very short, consistent with the 3 to 4 minutes expected based on the modeling of a marine landslide compared to the 15 to 60 minute periods for an earthquake-induced tsunami.
Last week was the annual American Council of Engineering Companies of Arizona Roads and Streets Conference in my home town of Tucson, Arizona. Its a transportation themed conference as you might guess, but there are usually a few geotechnical-type presentations. This year, there was an excellent presentation on the SR 87 Landslide that occurred about 1-year ago on the highway between Phoenix and Payson. The presentation was given by Keith Dhalen, PE with AECOM , Wayne Harrison, RG also with AECOM and Scott Neely, PE with Terracon . Read on for my recap of the presentation. (Photo by ADOT via AZGS)