Within Google Scholar you can restrict your search to EarthArXiv by inputting site:https://osf.io/preprints/eartharxiv * into the search box. In this example, the * means "any paper from the site https://osf.io/preprints/eartharxiv" so you’d get all Google Scholar papers that originated from EarthArXiv. Alternatively, you could replace the * with other search text such as site:https://osf.io/preprints/eartharxiv earthquake to find all EarthArXiv papers on Google Scholar with earthquake in the title or text.
Another interesting search is to use EarthArXiv in quotes. "eartharxiv" forces the search to use only 'eartharxiv' and not look for partial matches like 'arxiv' and 'earth'. However, this search will show results originating from other sites and won’t limit the results to those originating from https://osf.io/preprints/eartharxiv. It is an interesting compliment to the query above as it will show papers from other repositories that contain the text “eartharxiv”.