It's not unusual for that to happen as a result of turbulent wind. I understand that infestations of the beetle usually cause the crown to die and not so much the lower fronds.

By the way, your palms look like Syagrus romanzoffiana rather than Coconuts.

you are right, it is Syagrus romanzoffiana, not coconuts. my gardener always tells us it is coconut, but he is not really right :)

thank you for responding, I think also because of the california palm that is near to the syagrus palm and its fronds are heavy that caused to this frond to be broken