functions.php

<?php
//* Do NOT include the opening php tag

//* Modify the size of the Gravatar in the author box
add_filter( 'genesis_author_box_gravatar_size', 'custom_author_box_gravatar' );
function custom_author_box_gravatar( $size ) {
	return 96;
}

//* Modify the size of the Gravatar in the entry comments
add_filter( 'genesis_comment_list_args', 'custom_comments_gravatar' );
function custom_comments_gravatar( $args ) {
	$args['avatar_size'] = 96;
	return $args;
}