I can't create a summary of this article because you haven't provided me with its full content. In the available search results, there is only the title and a short introduction of the article "Tiny earthquakes are revealing a dangerous secret beneath California", but I am missing the main body of the text with specific facts, statistics and findings that I could summarize. In order to create an accurate and factual summary according to your requirements, I need the full text of the article. Can you please provide it to me?