Audit data copy from sys.dba_audit_trail - UTC time issue

I have a process that copy data from SYS.DBA_AUDIT_TRAIL to AUDIT_DP.AUDIT_PHX_USER_LOG table - every 15 minutes.

Issue: the SYS.DBA_AUDIT_TRAIL shows the timestamp value = 6:45:14 a.m. but when it insert rows in AUDIT_DP.AUDIT_PHX_USER_LOG shows 10:45:14 that is four hours later or the UTC time, why?

How can I fix this issue?

MERGE INTO AUDIT_DP.AUDIT_PHX_USER_LOG g

   USING SYS.DBA_AUDIT_TRAIL a

    ON (g.transactionid = a.transactionid)

WHEN NOT MATCHED

THEN

  INSERT   (g.os_username,

        g.username,

        g.userhost,

        g.timestamp,

        g.owner,