Frequent sediment density flows during 2006 to 2015, triggered by competing seismic and weather events: Observations from subsea cable breaks off southern Taiwan

The 2006 Pingtung earthquakes produced the largest sediment flow(s) that produced 22 cable breaks. The other events were less destructive with each causing 6-9 breaks. Sources of the sediment flows varied with the triggering mechanism: those associated with hyperpycnal discharges probably began near the mouth of the Gaoping River. In contrast, earthquake-triggered landslides and subsequent sediment density flows formed anywhere on the adjacent continental margin. Flow speeds generally declined with increased run-out, lower seabed slope and increased channel width. Most variability (7-20 ms− 1) was observed over the 0.4°-1.0° slopes of Gaoping Canyon but speeds were mainly restricted to 5-8 ms− 1 in the 0.3° sloping Manila Trench. The 2006-2015 period of frequent cable-damaging flows is the first for the past two decades or longer. In the absence of evidence for increased seismic or anthropogenic activity, this disruptive period may reflect increased typhoon intensity and fluvial sediment discharge. Such typhoon-related flows may complicate interpretation of palaeo-seismic records derived from turbidites in such settings.