The phrase "are usually explained by" is correct and usable in written English.
It can be used when discussing the reasons or causes behind a particular phenomenon or concept.
Example: "The variations in climate patterns are usually explained by changes in ocean currents and atmospheric conditions."
Alternatives: "are typically accounted for by" or "are generally clarified by".
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.
Difficult actions (eg Jill's riding a unicycle) are usually explained by appealing to enabling factors (eg She practiced a lot).
These social disparities in the process of educational attainment are usually explained by differences in the parental social status.
Natural rubber (NR) exhibits great fatigue properties which are usually explained by its ability to crystallize under strain.
While the negative storms are usually explained by the storm-time thermospheric composition changes (e.g., Fuller-Rowell et al. 1994; Prölss 1995), the positive storms remain less certain.
The antagonistic properties of matsoun are usually explained by its acidic pH, because of synthesis of carboxilic (lactic acid particularly) and fatty acids (Dalie et al. 2010; Falguni et al. 2010).
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.
Hull's cheapness (and presumably Southport's and Barrow's too) is usually explained by the lack of career and leisure opportunities here, in turn put down to our isolation from Britain's economic centres.
Why this should be so is usually explained by two things: the gyroscopic precession caused by the spinning front wheel, and the castor effect resulting from the front wheel's contact point with the road trailing behind the steering axis of the front forks—in much the same way that the trailing wheels of a shopping trolley allow it to be steered easily.
This is usually explained by Hergé's "naivety", as an author of children's comics (a defence also used for P.G. Wodehouse).Alas, none of those arguments survive a reading of a biography of Hergé by Philippe Goddin, published in 2007.
This is usually explained by the hubs being the nodes that are primarily responsible for maintaining overall connectivity.
