Question 1196929
your formula states that:
M = log(E) - 11.8 / 1.5
since log(E) = log(10^26) = 26, the formula becomes:
M = 26 -  11.8 / 1.5
that becomes:
M = 18.13 which is unreasonable, since the richter scale doesn't go up that far.
i believe the formula should be:
M = (log(E) - 11.8) / 1.5
the log(E) - 11.8 needs to be in parentheses to show that the whole expression is in the numerator.
the formula then becomes:
M = (26 - 11.8) / 1.5 = 9.466666......
round to two decimal places to get M = 9.47
that looks more reasonable.
from M = (log(E) - 11.8) / 1.5, solve for log(E) to get:
log(E) = 11.8 + 1.5 * M
when M = 7, the formula becomes:
log(E) = 11.8 + 1.5 * 7 which becomes:
log(E) = 22.3
this is true if and only if E = 10^22.3


your first answer is M = 9.47 rounded to 2 decimal places.
your second answer is E = 10^22.3


let me know if you have any questions.
theo