Question 3: (a) Given that the rate of convergence between the Juan de Fuca and

Question

Question 3: (a) Given that the rate of convergence between the Juan de Fuca and North America Plates at the Cascadia Subduction Zone is 4 cm/year and that the thrust fault at the subduction zone has been completely locked since the last great earthquake in 1700, what slip distance could be expected if a megathrust earthquake occurred today and released all accumulated deformation? (5 pts) (b) The locked portion of the thrust fault between the subducting Juan de Fuca Plate and the over-riding North America Plate is approximately 1000 km long and 100 km wide, and the shear modulus of the rock is = 4.5 x 1010 N/m2. Compute the moment magnitude for a megathrust earthquake that ruptures the entire fault, assuming the slip you computed in part (a). (10 pts)

Explanation / Answer

a) here the slip distance is = total distance / total time required

here the distance between juan de fuca and north america is approx 200 kms

the time seased after 1700 till today is approx 300 yrs so 200/300 = 0.66km/ year is the rate of slip distance

b)  the moment magnitude scale is M = (log10(M0) - 9.05)1.5

= (log10 (4.5*1010) -9.05)1.5

=(10.65-9.05)1.5

= 1.06

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