accumulation vs. concentration

always not so sure can accurately understand the nuance between the two concepts, that accumulation of risk, is well defined in the glossary section, i.e. a single event leading to claims from a number of policies, but seems not get the clear definition of concentration risk from the notes of ActEd for SP7.

e.g. regarding a CAT, that may result in claims from various policies of different lines, say, household book, commercial property book, construction book etc., so that is an accumulation of risk. meanwhile, if the company have policies in a particular location, we may say it exposes to concentration risk in terms of location, exposing to a CAT.

so, seemingly the concept of accumulation and concentration can be used interchangeably? or have some nuances? not so sure, especially in the context of capital setting processes. thanks for advise!