When Is the Big One Coming?

On April 18, 1906, at 5:12 a.m., people living around the San Francisco Bay Area woke to the earth trembling. Twenty seconds later, the ground began to roll as an earthquake with an estimated 7.9 magnitude rocked the coast of northern California. With an epicenter near San Francisco, the shaking reached from Los Angeles to Oregon and as far east as central Nevada.

A minute later, the ground was still, but the upheaval in the city had just begun. Percy Gregory, an immigrant carpenter, wrote to his mother, “The Hills rolled like great billows and cracked open, houses sank between seven and eight feet in places. All the big cheap lodging houses collapsed with all the people in them. Then the fire which started in one hundred places—at once quickly burnt-up the dead and injured.”1

Besides inflicting catastrophic structural damage, the quake had ruptured both gas and water mains. As devastating fires broke out across San Francisco, the firemen had no access to water to extinguish the flames. The inferno tore through the city, lasting for several days and burning over 450 blocks. More than 3,000 people died, and over 80% of the city was destroyed. By today’s estimate, the earthquake cost $16 billion in damages. It remains one of the worst and deadliest earthquakes in US history.

During the 116 years since that catastrophe, the San Francisco Bay Area has grown into a sprawling metropolis, the center of tech companies like Pixar, Apple, and Facebook, and beloved for landmarks such as the Golden Gate Bridge, Alcatraz, and Lombard Street, one of the crookedest streets in the world.

But beneath the bustle of prosperity and the allure of tourist attractions hangs the reality that the next “big one” could disrupt life as Californians know it. News sites often predict the potential devastation of an earthquake that would be cataclysmic in the region, akin to the Yellowstone volcano exploding again.

The alarm is palpable because California has a recorded history of many devastating earthquakes. Indeed, signs indicate that even earlier catastrophic earthquakes have occurred along the San Andreas fault line and other fault lines connected to it.

But does the biblical account of earth’s history confirm the headlines about California’s tremulous history? Or is talk of California’s imminent “big one” just media hype?

San Andreas in Scripture?

The earth’s surface has been broken into ginormous segments of the earth’s crust (its outer “skin”) called plates. From the biblical account of earth’s early history, we can infer that originally the landmasses formed a supercontinent. If all the waters on day three of creation week were gathered together in one place at God’s command, then it is likely that all the dry land was in one place (Genesis 1:9).

We are told that the global flood cataclysm was initiated by the fountains of the great deep breaking up (Genesis 7:11). We can infer that “breaking up” describes the rifting apart of the supercontinent into the plates that then raced catastrophically across the earth’s surface as God reshaped the earth with his flood of judgment for man’s sin (Genesis 6:11–13).

The catastrophic plate movements during the flood established the present configuration of continents, which today move imperceptibly against one another. The continents are mostly pushing apart at mid-ocean ridges or colliding at the opposite sides of the plates, but across California the plate edges are sliding past one another. These earth movements are called plate tectonics.

Why California?

The 1906 San Francisco earthquake ruptured about 270 miles (430 km) of northern California along the northern segment of a major fault line known as the San Andreas fault. This major “wrench” across the earth’s surface is visible for roughly 750 miles (1,200 km) through California.

1. The San Andreas Fault

The San Andreas fault line extends approximately 750 miles (1,200 km) through California.

The San Andreas fault marks the boundary between the Pacific and North American plates. Along the fault, the Pacific plate is sliding horizontally northward against the North American plate, which is moving southward. The actual sliding or slip rate along the fault ranges from 0.79 to 1.38 inches (20 to 35 mm) per year.

When the global flood ended over 4,300 years ago, the Pacific plate was sliding past the North American plate along the San Andreas fault. However, like all other geologic processes that had been operating at catastrophic rates during the flood, the plates have been rapidly decelerating during the thousands of years since the flood.

This boundary between these two plates is more complicated than just one fault line dividing them. Because of the enormous amounts of energy involved in these plates sliding past one another, the ground has been torn along other fault lines that branch laterally at various angles to the main San Andreas fault. That means earthquakes can also be generated along those faults. In fact, some of these faults were only discovered when earthquakes occurred.

Additionally, major faults inland, such as the Hayward and Calaveras faults, parallel the San Andreas fault on the Californian edge of the North American plate. Some of those are also still occasionally active in response to movements on both the San Andreas and related faults. However, other faults near the edge of the North American plate have also experienced residual vertical adjustments during the aftermath of the flood.

Fault lines web across the United States, but most are inactive because they were produced within the North American plate during the flood after the sedimentary layers that cover the continent were deposited. Today, the ground within the North American plate is relatively stable. But not so at the plate margin in California, an area that has seen a cycle of earthquakes along the active fault lines.

A Deadly Cycle

After the 1906 San Francisco earthquake, geophysicist Harry F. Reid investigated the displacement of the ground surface along the nearby San Andreas fault in the 50 years before the earthquake. He found evidence of 10.5 feet (3.2 m) of bending during that period. He correctly concluded that the earthquake must have been the result of the elastic rebound of the strain energy stored in the rocks on either side of the fault when the rocks ruptured and moved.

The rate of movements of the Pacific and North American plates along the San Andreas fault are not uniform, and the strengths of the rocks differ. The San Andreas fault has northern, central, and southern segments with different risks in the frequency and intensity of potential earthquakes.

It takes time for the strain energy to build in the rock masses, so earthquakes along the San Andreas fault and its related branch faults have occurred in repetitive cycles. It’s like bending a wooden ice cream stick. You can only bend it so much before it snaps.

Predicting the Next Big One

The San Andreas fault is the only such major fault where the plates are actively sliding past one another.

The San Andreas is one of the best-studied fault lines in the world—and for good reason. Remarkable for its length and size, the San Andreas fault is the only such major fault where the plates are actively sliding past one another.

It makes sense to study a fault line that threatens roughly 26 million people concentrated along the Californian coastal strip. The more we learn about the San Andreas fault, the more we can reduce the potential astronomical human and financial tolls from large earthquakes.

Between 2002 and 2007, a deep borehole was drilled near Parkfield, CA, down 2 miles (3.2 km) and through the fault zone to establish the San Andreas Fault Observatory at Depth. Instruments placed by geologists down the borehole monitor the strain buildup in the rocks. The aim is to understand the fault and predict future earthquakes.

So far, predictions of earthquakes have not been very successful. Because we cannot be sure of how much and where strain energy has accumulated along the faults, we can’t know just when and where the rock layers will break.

One thing is sure: because the plates are still sliding past one another along the San Andreas fault, there will always be future earthquakes. The longer the time between earthquakes, the more strain energy will build up on the faults, so the bigger the resulting earthquakes will be when the rock masses finally rupture. Many smaller earthquakes are better to endure as damage and loss of life is far less likely. And thankfully, lots of smaller shakings occur regularly in California, releasing that strain energy in relatively harmless quakes.

3. The History of Californian Earthquakes

Click to view enlarged image.

Is the “Big One” Coming?

Today’s California earthquakes are a leftover from the flood cataclysm as the earth continues to settle down. This implies that, with time, as plate movements slow down further, the risk of earthquakes may well decrease. Similarly, historical evidence indicates the frequency and size of volcanic eruptions have decreased with time.

However, as long as the plates are moving, we cannot rule out the possibility of another “big one.” The longer the strain energy builds up on these California faults, the greater the potential for a catastrophic earthquake to occur. That means we should be thankful when frequent smaller earthquakes occur to alleviate the stress on the rocks.

We cannot rule out the possibility of another “big one.” The longer the strain energy builds up on these California faults, the greater the potential for a catastrophic earthquake to occur.

However, even though there have been more than 5,000 small earthquakes in the San Francisco Bay area over the past year, we simply don’t know how many small earthquakes are needed to relieve the accumulating strain energy. The current awareness of the potential for another “big one” is more about the fact that historical records indicate that the larger earthquakes occur about every 25–50 years. Since the last big quake on the San Andreas fault shook up the area in 2004, maybe another “big one” is due.

Californians should be aware of the forewarnings from experts, such as the US Geological Survey professionals studying the San Andreas and related faults of California.

Should the “big one” happen, there is no question that the devastation would be horrific, with an untold loss of life and financial cost that could tally into the hundreds of billions. The ground movements and prolonged shaking would demolish buildings, freeways, and bridges and trigger landslides. Water would be contaminated and electricity supplies would be cut off. Supply chains would be disrupted due to demolished road and port systems.

The San Andreas fault is mostly located on land, but if the earthquake was centered offshore, a tsunami would sweep across the coast, wiping out nearly everything in its path. Furthermore, a large San Andreas fault earthquake would potentially affect other nearby fault lines, triggering additional earthquakes. However, it’s unlikely that other fault lines further away in the US, such as in Alaska, would be affected. The devastation would be likely confined to California and nearby areas.

4. How Does an Earthquake Happen?

Building

The two sides of an active fault are initially locked together, but the ground is slowly moving in different directions. As the ground moves, elastic strain energy builds up in the adjoining rock masses. If a road is built straight across the fault, it is perpendicular to the fault trace where the fault is locked.

Straining

The fault movement puts increasing strain on the rock masses on either side of the locked fault. This strain energy may accumulate by movements of only an inch per year.

Breaking

Eventually, the accumulated strain overcomes the strength of the rocks, causing a sudden break as the ground springs back toward its original position. The jolt is felt on the surface as an earthquake. This sudden movement shifts the roadway’s surface.

When the Quake Comes

By 1915, only nine years after the earthquake, San Francisco was largely rebuilt, risen from ashes and rubble. Now one of the most iconic places in the world, the city by the bay reminds us of humankind’s resilience and God-given ability to innovate.

Since the 1906 earthquake, building codes now require architecture designed to withstand or mitigate the force of an earthquake. Contractors implement less flammable material and fewer brick designs that easily collapse.

Citizens in seismically active areas are cautioned to keep an earthquake survival kit handy, to practice earthquake drills, and to develop an emergency response plan. Though we cannot predict earthquakes, we can wisely prepare for them.

Though the Earth Shakes

Today in San Francisco, you can watch sea lions sunning themselves on Pier 39, grab a slice of famous sourdough bread, watch cable cars climb the steep hills, and spot the dense bay fog cloaking the Golden Gate Bridge. Little indicates the formerly ravaged city—or the potential calamity that might once again befall it.

We can look to the San Andreas fault and its resulting earthquakes as evidence of the global flood of judgment that ruptured the earth and destroyed all life except for Noah’s family and the creatures on the ark. Those who have trusted Christ as Savior can rest assured that they will never face God’s eternal judgment for sin.

Still, we can never be sure what tomorrow holds, whether it’s the “big one” in California or a personal tragedy in our hometown. But we can say with the psalmist, “God is our refuge and strength, a very present help in trouble. Therefore we will not fear though the earth gives way, though the mountains be moved into the heart of the sea, though its waters roar and foam, though the mountains tremble at its swelling. Selah” (Psalm 46:1–3).