mysql insert event trigger fired at update event

I create a 'after insert' trigger,but it triggered when update the table. can someone tell me the reason ?

mysql version    :5.6.23-log
trigger event    :INSERT
trigger statement: 
             `BEGIN INSERT INTO t_trigger_sync_to_ec(table_name, pk, pk_value, ctime, utime,act) VALUES('t_transact_user_info', 'f_id', NEW.f_id, NOW(), NOW(),'insert');END`

bin log: Log1 Log2