occurring
v. 发生；存在于（occur 的现在分词）
例句
After May 19, strikes were occurring on a daily basis.
在5月19日以后，罢工每天都在发生。
《柯林斯英汉双解大词典》
It was noticed that this strange thing had been occurring every day latterly.
大家注意到，近来这种怪事天天都在发生。
Even more than mountainside slides of mud or snow, naturally occurring forest fires promote the survival of aspen trees.
自然发生的森林火灾甚至比山体滑坡或积雪更能促进白杨树的生长。
