Mark 11:23, Seneca, and Earthquakes

For my write-up today on Robert Grant's Miracle and Natural Law in Graeco-Roman and Early Christian Thought, I'll focus on Grant's comments regarding Mark 11:23, which states (in the KJV): "For verily I say unto you, That whosoever shall say unto this mountain, Be thou removed, and be thou cast into the sea; and shall not doubt in his heart, but shall believe that those things which he saith shall come to pass; he shall have whatsoever he saith."

Grant reads Mark 11:23 in light of Zechariah 14:4, which states: "And his feet shall stand in that day upon the mount of Olives, which is before Jerusalem on the east, and the mount of Olives shall cleave in the midst thereof toward the east and toward the west, and there shall be a very great valley; and half of the mountain shall remove toward the north, and half of it toward the south."  Grant notes that the Hebrew word for "toward the west" is literally "to the sea".  Grant's point is that Jesus in Mark 11:23 is talking about the fulfillment of eschatological promises about the moving of mountains.  Presumably, in the same way that Jesus through his ministry was fulfilling eschatological promises in the Hebrew Bible about (say) the blind seeing, so likewise did Jesus believe that his disciples would carry out other eschatological promises through their faith.

Grant contrasts the attitude in Mark 11:23 with that of the first century Roman Stoic Seneca, who in Scientific Problems said: "Countless 'miracles' move and change the face of the earth in various places, bring down mountains, raise plains, swell valleys, raise up new islands in the deep.  It is worth while to investigate the causes from which these things happen.  You may ask, 'What will the value of their endeavor be?'  The greatest value of all, to know nature."

Grant believes that there is a difference between Seneca and Jesus: "The event, an earthquake, is presumably the same in each case.  Seneca sees in it an occasion for scientific investigation or philosophical speculation; Jesus looks forward to it as an event in which the hand of God will be revealed."

I guess one could then ask the question: Could an earthquake (not all earthquakes, but an earthquake) be both a sign caused by God, and also something natural, since God can use nature?  In my opinion, if an earthquake is the result of natural causes that build up, that somewhat undermines the notion that God is simply causing earthquakes by snapping his fingers.