Your weight is (roughly) proportional to the inverse of the square of the distance you are from the center of the earth. If that distance is reduced to 1/4 its previous value, then your weight will be multiplied by the factor ...
1/(1/4)² = 16
You would weigh 16 times as much.
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<em>Additional comment</em>
The distribution of mass within the earth also affects your weight.
