The recent earthquakes in Ecuador and Japan occurred on the boundaries of the Ring of Fire - a horse-shoe shaped string of more than 450 volcanoes along the Pacific coastlines of four continents.
The US city of San Francisco is on this boundary with two major fault lines nearby - the Hayward and San Andreas. CCTV correspondent has more on the city's preparations for the next big one.
It's the stuff Hollywood dramas are made of. The 2015 action film, San Andreas, shook global audiences with scenes from a monster quake that destroys big chunks of LA and San Francisco.
In 1906, 80-percent of San Francisco was destroyed in a 7.8-magnitude earthquake. And in 1989, 63 people died in one measuring 6.9.
"You see all the merchants, all the stuff falling off. I remember my mom holding her Buddha, my wife holding three kids on the back. That's not well prepared. Then, from then on, I think we better prepare for it," said Tom Hui, Director of San Francisco Dept. of Building Inspection.
When the 1989 quake struck, Tom Hui was on the second day of his new job at the Building Inspection department.
Today, as director, he spearheads a mandatory program to retrofit more than 5-thousand soft story buildings - ones with wood frames and at least three stories and five units.
"You can do seismic upgrade the whole building, but the cost will be so much and the tenant displacement is another concern. That's why we determine only do ground floor to strengthen it and prevent the collapse of the ground floor like the '89 earthquake," said Tom Hui.
That's spurred into action contractors like John Pollard, who shows me details of the ground floor retrofitting for this 8-unit building, which has three floors above.
"You see this area right here. This is called a dog ear. We sculpt out this in the steel right here to actually not make it too strong. What we wanna do is to have the building be able to bend. If we keep it thick, then the building will start to snap and crackle. It's not that difficult it's just time and money. There's a lot of components,"
"People think oh you're just throwing up plywood, but as you can see, it's a 2 x 6 wall, there's a double top plate, we've got electrical, we've got plumbing through it, we've got multiple clips hold downs in the corner, so there's 20 different components. Believe it or not, each one of these walls cost us 4 or 5,000 dollars," said John Pollard, contractor of San Francisco Garage Company.
As the retrofitting goes on, the owner of this building has decided to clear out the garage and storage here and add four new units. That will generate extra cash flow that could help offset the cost of retrofitting in the long run.
"We have ten years of work-probably have about 35 projects going at the same time."
Innovation is also connecting seismology to Silicon Valley tech. Ross Stein, a 35-year veteran of the U-S Geological Service, has helped create Temblor, a mobile web app that calculates the seismic risk of your precise address.
It shows nearby faults, risk of quake damage, liquefaction and landslide potential, and supplies you with a cost-benefit analysis of retrofitting.
"If you do it because you have to do it, you do it as cheaply as possible. And you wait as long as possible, until you absolutely have to do it, like our taxes,"
"So the alternative is to say, look, most of us have our biggest investment in our homes, and the most precious people on earth to us live in those homes. So we wanna keep our families safe and we wanna keep our principal investment sound," said Ross Stein, Co-Founder & CEO of Tremblor.
Temblor even shows us that in San Francisco, the entire financial district - and an area booming with tech startups called 'SOMA' - are built on fill that provides no stability during an earthquake.
Mark says: "Are they aware of that?"
"Oblivious. We all tend to ignore the earthquake peril. Ask yourself this, when were you at a bar where you saw the liquor bottles being restrained that wouldn't fly off in an earthquake like missiles of broken glass You basically can't find it,"
"If you go to Japan, you can't find a bar that does not restrain its alcohol bottles. This is a pretty good Rorschach test that we're all ignoring what will certainly come again here," said Stein.
Stein says city infrastructure upgrades since 1989 are at best "half" of what's necessary. Part of the reason is that higher magnitude quakes have not hit California in recent years, lulling people into complacency about precautions that could save their lives.
