The Great Shake of 68

September 12 - November 25, 2006

The rumbling preceding the shock came very distinctly from the bay, and the plain in that direction rolled like huge waves of the sea coming toward Haywards.—F. Allen

We know California is earthquake country but a shock large enough to make us look for cover does not happen often enough that we think about it everyday. Have no doubt though, earthquakes happen here. The last time the Hayward fault had a major eruption was in October 1868. An estimated 7.0 magnitude quake rumbled through the area. Destruction was widespread. Falling debris injured and killed several people. Buildings slid from their foundations or collapsed, chimneys fell, and water wells ran dry. Prior to the 1906 earthquake on the San Andreas Fault, this was the one everyone called "The Great Quake." It forced area residents to acknowledge that earthquakes are a fact of life here and can happen at any time.

What was the Hayward area like back then?

In the 1860s, the Hayward area consisted of several tiny, rural communities with a few farms and businesses. Hayward was the largest town. A few square blocks centered around the Hayward's Hotel on A Street made up the entire business district. Former gold miners and new immigrants who found the area a perfect location to open businesses and start farms made up the population of several hundred people. Roads, landings on the Bay, and finally the railroad in 1865 provided multiple routes for shipping grain and other products to the big city of San Francisco.

What happened during the earthquake?

There was yesterday another of those convulsions of nature which reminds men of their own weakness and of the frailty of their works.-Oakland News, October 22, 1868

At approximately 7:50 a.m. on the morning of October 21, 1868, the ground began shaking. Residents just starting their day ran frantically from their homes and places of work. They dodged flying plates, falling debris, and teetered on unsteady staircases and floors. A crack appeared in the ground suddenly, not far from the Hayward's Hotel, spitting water and sand. About forty seconds later, when the shaking and rumbling stopped, buildings throughout the Hayward area lay in ruins.

What was the damage?

Houses rocked and swayed like vessels in a trough of the sea, and the wildest confusion and excitement ensued. - Alameda Democrat, October 24, 1868

Almost every building in the Hayward area suffered damage from the earthquake. Several commercial buildings collapsed. The roof of the large brick Edmondson's Warehouse fell onto the bags of grains stored inside, pushing the walls outward. The falling debris crushed the livery stable next door. The flourmill of Morse & Heslep tipped over and the railroad station nearby did the same. Only one house chimney survived the event; the rest broke off at the roofline. Many businesses and homes slid from their foundations or collapsed into basements. Plaster and mortar cracked and crumbled away from walls, and the few adobe buildings in town fell. Communities from Santa Rosa in the north to Gilroy in the south and from Stockton to Half Moon Bay reported severe to moderate earthquake damage.

What happened after the shaking stopped?

As it seemed to be the impression of most persons that we were to have another big shake, rooms were at a discount and haystacks and straw piles in demand about dusk.-Alta California, October 23, 1868

Aftershocks continued to rattle the crumpled buildings, and the nerves of residents, throughout October 21. In the following days, cleaning up, evaluating, and rebuilding began. In the Hayward area, most of the buildings that collapsed, such as Edmondson's Warehouse, were rebuilt within a few months. Damaged homes and other buildings were either repaired or demolished. In San Leandro, the Alameda County courthouse temporarily relocated to a nearby vacant building and within five days, was once again conducting county business. Throughout the Bay region, the recovery and rebuilding moved at a rapid rate.

What did people learn from this earthquake?

At the time, Bay Area residents learned some valuable lessons from this disaster. Many newspaper accounts and editorials stated that buildings built poorly using cheap materials or those not secured to their foundations were the ones most likely to be harmed in an earthquake. They also noted buildings constructed on made ground or landfill suffered the greatest damage. Some editorials encouraged the city of San Francisco to outlaw the use of decorative details on buildings because people suffered injuries from falling debris.

No one published an official study looking into construction techniques and earthquakes because of this event. A few people did take the newspaper reports to heart and changed the way they built buildings in the ensuing months and years. In San Lorenzo, William Meek constructed his large home in 1869. The house contains extra wall supports and crossbeams to make it more stable in the event of an earthquake. It is not known whether Mr. Meek asked for these additions or if the builder added them on his own. Regardless, the mansion still stands today as a testament to stronger building practices.

What do scientists know today about the 1868 earthquake?

Scientists can tell us a lot about the 1868 earthquake and the Hayward fault. The earthquake was around magnitude 7.0. The Hayward fault extends roughly 50 miles from San Pablo Bay to the Santa Clara County border. The 1868 quake was on the southern segment. The Hayward fault is a right lateral strike-slip fault. It creeps at a minute rate every year.

This earthquake happened so long ago, how do scientists know anything about it?

They study historical documents like newspapers to read first-hand accounts of what happened during and after the event. This information gives them an idea of the intensity of the quake, how much damage it caused over how far of a distance, and what the motion of the quake felt like. They also use modern tools like aerial photography and computer simulations along with tests conducted along the fault. All of these tools give scientists a way to understand this earthquake and its effects.

When did scientists start to study earthquakes?

Scientific study of earthquakes in the U.S. really began after the 1906 earthquake. That event so devastated the entire metropolitan region of San Francisco that it spurred the development of modern earthquake science. Applying what they know now, scientists study historical earthquakes to help understand, and possibly predict, future events.

What causes earthquakes?

The earth's crust is broken into several pieces called tectonic plates that slowly slide and grind against each other. California straddles the boundary where two of these plates meet. The edges of the plates, known as plate boundaries, contain faults, which are fractures deep in the earth. As the plates move, their rough edges get stuck on one another, building up pressure. When the plates move far enough, the edges unstick on one of the faults. The movement releases energy in the form of seismic waves that travel through the earth. When the waves reach the earth's surface, they cause the shaking we feel during an earthquake.

How are earthquakes measured?

Earthquakes shake at different rates and scientists use various methods to measure their size. The most well known method for measuring earthquakes is the Richter scale. Seismographs record the amount of energy each earthquake releases and a number is then assigned to it based on this scale, called magnitude. A jump in one number on the magnitude scale represents a 10-fold increase in the amount of energy released. For example, a 5.0 magnitude earthquake is ten times stronger than a magnitude 4.0.

Scientists also measure the intensity of an earthquake using the Modified Mercalli Intensity Scale. Intensity describes the strength of shaking. It is determined by observing the physical effects of the shaking on people, buildings, and the environment. The scale created a uniform system of description with rankings from I to XII. The 1868 earthquake had an intensity of X on the scale.

What is a seismograph?

Instruments that record earthquakes are called seismographs. They record the shakes and jolts of the seismic waves of an earthquake and usually look like a series of squiggly lines. The magnitude of an earthquake is determined by the height of the squiggly lines, which represent the waves. Scientists can determine when and where an earthquake happened by seeing how long it took the waves to arrive at different seismographs located in different places around the area.

What is a strike slip fault?

There are several types of faults. The Hayward fault is a strike slip fault. This is where two tectonic plates are sliding past each other like cars traveling in opposite directions on the freeway. Literally, the area east of the fault, the hillside, is moving to the south, while the west side, the Bay side, is moving to the north. These types of faults are either right lateral or left lateral. The Hayward fault is a right lateral. A right lateral strike-slip fault is one where no matter which side of the fault you stand on, the side farthest from you is moving to the right. The other main types of faults are dip-slip or thrust faults. These are where the plates are either pushing together or pulling apart causing one side to either slide up or down the other.

What do scientists say about the Hayward fault today?

"… there [is] a fundamental problem with earthquakes: They refuse to operate on human standard time. They're on their own peculiar schedule. Earthquake faults have a nasty way of combining patience with impulsiveness. Wait, wait, wait-lurch."-National Geographic, April 2006

The Hayward fault has not erupted significantly since 1868. For 138 years, the fault has slowly crept along, moving minutely every year. The creeping releases some of the tension on the fault, but scientists do not believe that it has been enough. In fact, currently scientists estimate that there is a 27% probability that the Hayward fault will create an earthquake of magnitude 6.7 or greater, in the next 30 years. It is potentially the most dangerous fault in the entire Bay Area region.

What can we do?

"People still die in stunning numbers when the ground beneath their feet begins to shake. Almost always it's not the earthquake that kills them, but rather their collapsing homes, offices, stores, and school."-National Geographic, April 2006

Between 2,000 and 3,000 people lived along the entire Hayward fault in 1868. Now, close to two million people live along the fault. There is a tremendous potential for significant loss of life and destruction of property along the fault and throughout the Bay Area because people and buildings are unprepared for a major earthquake. We cannot prevent earthquakes, but we can be ready for them.

Everyone should plan for the safety of themselves and their loved ones in the event of an earthquake.

• Create a disaster plan for your family. Make sure everyone knows what to do during and after an earthquake-how to drop, cover, and hold on; how to get home; and who to contact.
• Create disaster kits with enough food, water, medications, flashlights, blankets, and extra clothes for each family member and pet to last for a week. Also, keep an emergency supply of money and copies of all your important documents.
• Identify potential hazards in your home or place of work, such as furniture and hanging objects, and take steps to secure those items.
• Verify the stability of your home and work. Is your house bolted properly to the foundation? If you work in an older building, has the building been retrofitted? Take the necessary steps as soon as possible to make sure these buildings are safe.