Adding Title tag to Gravatar

How can I add a title=”” to the gravatar image in the author bio box that resides at the bottom of posts? I tried to edit display-about-author-block.php to no avail. This is what code is there:

<img alt="Chris Dill" src="https://secure.gravatar.com/avatar/4f5ae5de0427c2bb8c40dddd112f62cb?s=75&d=https%3A%2F%2Fsecure.gravatar.com%2Favatar%2Fad516503a11cd5ca435acc9bb6523536%3Fs%3D75&r=G" class="avatar avatar-75 photo" height="75" width="75" title="" data-pin-url="https://www.virginiaseo.org/blog/seo-resource-list-2014/">

And here is what I tried in the php to test (no variables) on line 277:

$author_image = '<img src="'.$author_image_url.'" title="Title" width="'.$image_size.'" height="'.$image_size.'" />';

thanks in advance!

https://wordpress.org/plugins/custom-about-author/