Multiple addresses in JSON-LD Schema.org

Similar to adding multiple string/URL values: by using an array.

<script type="application/ld+json">
{
  "@context": "http://schema.org",
  "@type": "Organization",
  "address":
  [
    {
      "@type": "PostalAddress"
    },
    {
      "@type": "PostalAddress"
    }
  ]
}
</script>