Of or relating to very slow crustal movements; bradyseismic.
From Greek 'brady-' (slow) and 'seismos' (earthquake), with the adjectival suffix '-ical'. This is an alternative form of bradyseismic.
You'll see both bradyseismic and bradyseismical in older geological texts—like many scientific words, the '-ical' variant felt more formal to 19th-century scientists.
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