Timing and Spouting Height of Sand Boils Caused by Liquefaction during the 2010 Mw 6.9 Yushu Earthquake, Tibetan Plateau, China

Abstract

The 2010 Mw 6.9 Yushu earthquake produced a ~33-km-long co-seismic surface rupture zone along the pre-existing active Yushu Fault on China’s central Tibetan Plateau. Sand boils occurred along the tension cracks of the co-seismic surface rupture zone, and locally spouted up above the ground to coat the top of limestone blocks that had slid down from an adjacent ~300-m-high mountain slope. Based on our observations, the relations between the arrival times of P- and S-waves at the sand-boil location and the seismic rupture velocity, we conclude that 1) the sand boils occurred at least 18.24 s after the main shock; 2) it took at least 4.09 - 9.79 s after the formation of co-seismic surface rupture to generate liquefaction at the sand-boil location; 3) the spouting height of sand boils was at least 65 cm. Our findings help to clarify the relationships between the timing of lique-faction and the spouting height of sand boils during a large-magnitude earthquake.