Yes. It is done with a filter on the appender.
Here is the appender configuration I normally use, limited to only INFO level.
<appender name="RollingFileAppender" type="log4net.Appender.RollingFileAppender">
<file value="${HOMEDRIVE}\\PI.Logging\\PI.ECSignage.${COMPUTERNAME}.log" />
<appendToFile value="true" />
<maxSizeRollBackups value="30" />
<maximumFileSize value="5MB" />
<rollingStyle value="Size" /> <!--A maximum number of backup files when rolling on date/time boundaries is not supported. -->
<staticLogFileName value="false" />
<lockingModel type="log4net.Appender.FileAppender+MinimalLock" />
<layout type="log4net.Layout.PatternLayout">
<param name="ConversionPattern" value="%date{yyyy-MM-dd HH:mm:ss.ffff} [%2thread] %-5level %20.20type{1}.%-25method at %-4line| (%-30.30logger) %message%newline" />
</layout>
<filter type="log4net.Filter.LevelRangeFilter">
<levelMin value="INFO" />
<levelMax value="INFO" />
</filter>
</appender>