Maria Graham's excerpt is from: Maria Graham, 1824, An Account of Some Effects of the Late Earthquakes in Chili, Transactions of the Geological Society, 2nd series, 24, 413-415.
Darwin's excerpt is from the famous voyage of the Beagle book: Darwin, C. R. 1845. Journal of researches into the natural history and geology of the countries visited during the voyage of H.M.S. Beagle round the world, under the Command of Capt. Fitz Roy, R.N. 2d edition. London: John Murray.
I cannot find any mention of Maria Graham account on the 1822 earthquake in Darwin's book.