The phrase "are usually explained" is correct and usable in written English.
It can be used when discussing how certain concepts, phenomena, or processes are typically clarified or described in general terms.
Example: "The principles of physics are usually explained through a combination of theoretical frameworks and practical examples."
Alternatives: "are typically described" or "are generally clarified."
Discrepancies between the short term statistics are usually explained by differences in when prices are measured (for example at mortgage approval or on completion) and the mix of properties.
Those restrictions on sovereignty are usually explained as deriving from consent or autolimitation, but it can easily be demonstrated that in some cases states have been considered as bound by certain rules of international law despite the lack of satisfactory proof that these rules were expressly or implicitly accepted by them.
Difficult actions (eg Jill's riding a unicycle) are usually explained by appealing to enabling factors (eg She practiced a lot).
Natural rubber (NR) exhibits great fatigue properties which are usually explained by its ability to crystallize under strain.
These social disparities in the process of educational attainment are usually explained by differences in the parental social status.
Astrophysical magnetic fields are usually explained in a framework of the dynamo theory, describing transformation of the kinetic energy of a flow into magnetic energy.
This is usually explained as being for family reunion purposes, but most travellers are not all that interested in their relatives in China.
The high rate is usually explained by the deteriorating health of the male population generally, but it may also be due to efforts by people like Mrs. Obraztsova.
In evolutionary psychology, anxiety is usually explained as part of the "fight or flight" reflex that gets triggered in the presence of danger.
Female characters in books, movies and on TV are meant to be likeable and, as nymag.com points out this week, if they're not, the problem is usually explained away as a medical problem (such as Homeland's Carrie being bipolar).
