Do a quick Google search for "how to survive a disaster." There are recommendations about everything from food and water storage to weapons and communication. A favorite topic is money, with warnings about the instability of paper currency and the benefits of stockpiling gold or silver. While global economic collapse can't be completely ruled out, past experience has shown that it's highly unlikely. Even after the worst disasters, financial systems are usually back up in a matter of days or weeks.
A better plan would be to prepare for short-term interruptions. Financial experts recommend having a three-day supply of cash on hand for disasters. That way you'll be able to buy things if credit card systems are down and you don't have access to banks or ATMs. That sounds simple, but when was the last time you had enough cash for three days' worth of food, gas and lodging?
For the longer term, you'll want to have three to six months of living expenses somewhere easily accessible, like in a savings or money market account. As an extra precaution, you could put some of that money into a financial institution outside your region so it's less likely to be threatened by the same disaster. Still want silver and gold? OK, but just remember that the price fluctuates daily and unlike money in a bank, it's not insured if lost or stolen.
Plus, if worldwide disaster strikes, the main liquidity issue you'll be worried about is finding clean water to drink!