I don't know how many times I've answerd those questions, yet here it goes again, with references.
Q: Does God cause natural disasters?
A: He can do it. Bible history says he did it a few times. Also tells us that God had a purpose when he did it, usually, to bring punishment upon wrongdoers. Floods (Genesis 6:17; 7:6), volcanic activity (Genesis 19:24, 25), droughts (1 kings 17:1), famines (Amos 6:4-9; Ezekiel 14:13; Genesis 41:22-32); disease outbreaks ( 1 Samuel 5:11, 12), sinkholes (Numbers 16:32); earthquakes (1 Samuel 14:15).
Q: Does God cause all natural disasters, then?
A: No, for there are other natural disasters recorded in the Bible and God isn't credited as having anything to do with them. (Amos 1:1; Zechariah 14:5; Acs 27:14-20)
Q: Can God prevent natural disasters?
A: I have no direct biblical proof of it; yet, if God brought the universe about and is "great in power and mighty in strenght", I have to assume that he has sufficient power to do such things. (Isaiah 40:26; Matthew 8:24-26) The Bible doesn't say that God ever stopped a natural calamity from happening, though.
Q: Can God at least forewarn people of impending great natural disasters that cause massive killings, such as earthquakes, tsunamis, volcanos, floods?
A: I believe God can and does forewarn people about great natural occurrences when they are originating from him because he is in control of such events. However, he appears to use discretionary power to choose who he wants to be forewarned, usually in favor of those who acknowledge Him as God. As for impending natural disasters that he has caused, He forewarned his servants and forewarned others, if He has as objective that they repent for salvation from punishment.
Q: Can God forewarn people about natural calamities that aren't being caused by him, then?
A: The future cannot be known because it doesn't exist. God cannot know a future that doesn't exist yet. However, God can calculate with great accuracy the probable outcome of the actions of people, and he also can cause anything to happen according to His will. In this sense, He can predict the future. So, probably God can predict an earthquake, if he decides He wants to measure how much pressure is building upon the edges of the tectonic plates or seismic faults; and likewise he can predict a volcanic event, or a flood, or just about anything else, even when he's not driving it, because he can access all data he chooses to. But that only happens only if God decides he wants to know such thing. Empirically, I'd say God chooses to not know such things before hand.
Q: But didn't God have an intervention in human affairs in Bible times?
A: The Bible says He did, especially in the OT. However, little - if any - intervention is shown after Christ returned to heavens. Some miracles performed by and for the apostles can show some limited evidence of discricionary intervention of Christ in favor of the Christian congregation. But God appears to be utterly absent from these actions; and if we strictly limit the scope of these events to natural disasters, then we see none.
Q: Why doesn't God intervein more actively in human affairs, especially now?
A: God has given humans free will and free choice to decide their course in life, whether they would choose to be led by God or lead their lives alienated from God. The only times God has interfered in human affairs was to defend and protect those who were loyal to him, and punish those who posed a threat to their existence. In those instances, sometimes he caused natural disasters. But empirically, we don't see that happening anymore. Thus we can conclude that, since the resurrection of Jesus, God restrains himself from direct intervention in human affairs that may pose a limitation to the human right of free will. That includes offering miraculous protection from natural disasters, for it would influence people's opinion about God, who would then be determined, not by love, faith and hope, as it's God's will, but by sight. - 1 Corinthians 14:13
Q: Isn't that unloving and uncaring from a God that has the power and the knowledge to act, but chooses to not know and not act?
A: Only God can answer that question fully. From a Christian believer prespective, God's ways are beyond our ability to fully comprehend them and God may well have ulterior, superior motives to allow for natural calamities to harm objectively good people and not taking action to prevent it or offer an escape. If God would use his discretionary powers to protect everyone's lives from every harmful situation, people would simply take God for granted. However, for the believer and the unbeliever there is hope of salvation in a spiritual domain, after earthly life is over. For that, one only has to put faith in Christ. And as for those who never could, never knew, or never had a choice of putting faith in Christ, God will offer a 'resurrection of judgement', where these ones may prove worthy of salvation, depending on their choices. That's not at all unloving nor uncaring. Until then, God teaches us to deal with the suffering, even the suffering caused by natural disasters such as the Tsunami of 2004, and expect us to put faith in salvation as generously extended by him. After all, before Adam and Eve there was no other expectation for humans other than the completion of the circle of life, without any hope for a brighter future.
Q: Since natural disasters cause human deaths, don't they reveal a design flaw by God?
A: They are only "disasters" from a human point of view. From a natural point of view they are simply natural occurences. Arguably, there wouldn't be life as we know it if it weren't for those natural "disasters" taking place. Quite possibly, there wouldn't be intelligent life on earth. If tectonic plates didn't get stuck and built presssure against each other, there wouldn't be mountains. In turn, the planet might be eternally under water. Perhaps we might have fish, but hardly any intelligent life. in any case, to assume that there was a "design flaw", you have to assume that tectonic plates were a product of design. Were they? And, to c&p what I wrote before, p erhaps that's the acceptable trade-off for life itself to exist. There's no absolute perfection in the universe except perhaps in the very person of God. "Perfection", in the relative sense, is something being optimally adequate to its purpose or function. In this sense, our world is adequate for producing and sustaining the life, even the intelligent life we find in it, therefore, "perfect". If you can produce me a world where material intelligent life came to existence, and where tectonic plates don't cause earthquaques and tsunamis and havoc and destruction, perhaps I'll be willing to revise my position.