You will have to write a script to delete them.

Ideally HADR should manage the set of log files automatically on the
standby, deleting or recycling (rename old and use as container for a
new one) them as needed.  It is intended to do this, but there are a
couple of known issues that may play in, causing accumulation of more
log files than desirable on the standby.

- APAR IY85138 - fixed in V8 FP14 and V9 FP2 - "First active log file"
not updated frequently enough on standby, causing retention/
accumulation of potentially many more log files than needed.

- APAR IY94994/APAR JR25834 - open - Log files are never deleted on
HADR standby, only recycled.  This results in the number of log files
retained on the standby only growing, never shrinking.

It is generally* safe to delete log files from the HADR standby that
have (a) already been archived (at primary), and (b) have a sequence
number lower than that of the first active log file.  DB2 itself will
normally consider such log files for removal (subject to implications
of config param LOGPRIMARY).

*- The risk involved in removing such log files is that they may be
required later in case of a rollforward operation or reinitialization
of the HADR standby.  In an HADR environment, log file archives made
at one site in an HADR pair must anyway be later accessible to the
other site for these purposes, so this is not a new requirement of
this particular scenario.

One can determine the first active log file at the standby from the
output of "GET DB CFG" issued there, for example:
      db2 get db cfg for <dbname-or-alias> | grep "First active"

Regards,
- Steve P.
--
Steve Pearson, DB2 for Linux, UNIX, and Windows, IBM Software Group
"Portland" Development Team, IBM Beaverton Lab, Beaverton, OR, USA