Arky Agoncillo (1982-00916)

Earthquakes are caused by the release of accumulated elastic strain energy due to sudden movements in the Earth’s crust. Earthquakes are mostly the result of ruptures in faults. A fault is a rock fracture wherein the rock on one side has moved relative to the rock on the opposite side. Strike-slip faults are a type of fault along which the movement is parallel to its orientation.

The San Andreas Fault is a strike-slip fault that runs across California at a length of approximately 1,300 kilometers. This fault is what is behind the two greatest earthquakes in the history of San Francisco: the 1906 “Great Quake”, and the “1989 Quake”. It is our hope that we come away with invaluable lessons from these two great quakes.

At 5:12 A.M. on April 18, 1906, the citizens of the port city of San Francisco were awakened by a tremor that would forever be remembered as one of the worst natural disasters in the history of the United States.

The epicenter was a mere 3 kilometers offshore from San Francisco and ruptured at a length of 477 kilometers along the San Andreas Fault.

The magnitude of the Great Quake was estimated to be at 7.9, but other records have it anywhere from 7.7 to as high as 8.25. The intensity was reported on the Mercalli scale at level VIII (destructive level) and up to level IX northward on the San Andreas Fault.

The tremor lasted for approximately 42 seconds with an aftershock of unknown magnitude following at 8:14 A.M.

Telephone and telegraph communications were cut off and the only exchange of information was through the use of messengers and soldiers.

Even the majestic San Francisco City Hall was not spared (sans its dome) of the devastating effects of the shaking intensity.

Unfortunately, though, the Great Quake was only the beginning of the disaster. The quake caused main water pipes to break and gas lines to rupture. Only the inevitable could happen next.

For immediately thereafter, the Great Fires of San Francisco began.

The horse-drawn fire carriages that the San Francisco Fire Department employed were simply of no match to the fires that engulfed the city into flames. The lack of water to fight the fires (due to the busted water mains) rendered the firefighters helpless.

The Great Fire raged on for 4 days and nights and ravaged the City of San Francisco. It is reported that some residents even burned down their own quake-damaged homes since their insurance only covered fire damage.

In the end, it was estimated that the quake and fires caused 3,000 deaths and damages were valued around $524 million (in 1906 dollars). It is also estimated that as much as 90% of the damage was caused by the fires.

On October 17, 1989 at 5:04 P.M., disaster struck in the middle of the afternoon rush-hour commute. The epicenter was located 123.2 kilometers south of San Francisco near Loma Prieta Peak.

The quake was caused by a slip on the San Andreas fault and lasted for approximately 15 seconds.

The magnitude of the quake was measured at 6.9 while the intensity was reported on the Mercalli scale at level VIII (destructive).

Of the 63 people who perished during this quake, 42 died during the collapse of the Cypress Street Viaduct on Highway 880. The upper deck collapsed, crushing the cars traveling along the lower deck.

A 15-meter section of the San Francisco to Oakland Bay Bridge collapsed and caused two cars to fall on to the lower deck. Miraculously, only one person was killed during this collapse. This busy bridge had to be closed for a month for repairs and is currently undergoing a major seismic retrofitting.

Occurrence Date and Time MagnitudeandIntensity

Death Toll EstimatedCost of Damage

1906The Great Quake

April 18, 19065:12 a.m.

7.9 MagnitudeIntensity VIII

Estimateddeaths at3,000

$524 million(in 1906 dollars)

1989Loma PrietaQuake

October 17, 19895:04 p.m.

6.9 Magnitude;Intensity VIII

63 dead;3,757 injured

$3 billion

DATE TIME MAGNITUDE DATE TIME MAGNITUDE

1/19/1989 6:53:26.91 5.30 10/17/1989 00:07:43.3 4.70

3/3/1989 7:04:01.78 5.00 10/17/1989 00:12:42.30 4.60

4/3/1989 17:46:34.23 4.50 10/17/1989 00:25:04.58 4.80

4/7/1989 20:07:27.82 4.70 10/17/1989 00:41:23.77 5.10

5/4/1989 03:37:41/08 4.60 10/17/1989 02:14:49.21 4.50

6/12/1989 16:57:15/86 4.50 10/19/1989 09:53:50.06 4.50

7/11/1989 04:13:33.72 4.60 10/19/1989 10:14:34.81 4.60

8/8/1989 08:13:27.39 5.40 10/21/1989 00:49:43.17 4.50

8/8/1989 15:53:28/07 4.50 10/21/1989 22:14:34.81 4.70

9/21/1989 17:41:18.43 4.90 10/25/1989 00:49:43.17 4.70

10/17/1989 00:04:15.19 7.00 11/02/1989 05:50:10.69 4.70

10/17/1989 00:07:15.29 4.70 11/03/1989 19:09:01.39 4.60

DATE TIME MAGNITUDE DATE TIME MAGNITUDE

1/19/2008 17:18:46.7 4.50 11/28/2008 13:42:18.46 5.90

1/19/2008 23:13:05.43 4.70 12/06/2008 04:18:42.81 5.08

2/21/2008 14;16:04.69 6.28 12/26/2008 12:19:40.02 4.50

2/21/2008 23:57:54.44 4.65

2/22/2008 06:40:10.95 4.56

4/26/2008 03:03:06.90 5.13

4/30/2008 17:18:32.10 5.40

5/06/2008 18:42:15.15 4.50

7/29/208 05:56:59.37 5.40

8/17/2008 09:27:22.34 4.60

10/26/2008 05:43:15.59 4.90

11/16/2008 13:42:18.46 4.60

While doing this project, it became apparent that the most important thing to come out of this is to learn from these disasters. Most importantly, what we should really know about earthquake disasters, its aftermath, and how to be better prepared for them. I decided to concentrate on the great quakes of 1906 and 1989 because I believe that we can learn the most from them. Also, I, myself, experienced first-hand the 1989 earthquake and I would like to share that experience in the hopes that other students may learn from it.

Studying geology is essential because it is through geology that we learned that the areas of San Francisco that suffered significant damage were built on soft landfill. We now understand that soft landfill areas are extremely vulnerable to the Earth’s intense movements. Since the 1989 earthquake, extensive retrofitting projects have been done throughout the marinas and the BART subway system. The San Francisco to Oakland Bay Bridge is also currently undergoing an extensive earthquake retrofitting.

A lot is said about the effects of earthquakes (and rightfully so), but very little is mentioned about the events that happen during the aftermath. As we learned from the 1906 quake, fire is a major concern after an earthquake because of ruptured gas lines. In the 1989 quake, ruptured gas lines inside homes caused the subsequent fires in the Marina District . It is therefore imperative that we all know how to shut off the gas valves in our homes. Be it an LPG tank or the main gas line to our dwellings.

As I experienced during the 1989 quake, there was no electricity, no gas, no water, no landline or cell phone service, no public transportation immediately after the tremor. I had to walk home from work (a good 2-3 hours), and did not have any idea as to what the extent of the quake damage was. When I arrived home, there was no electricity and so I could not watch or listen to the news. I had no idea if the rest of my family was safe because all of the phone lines were down. I could not even use the electric garage door opener to get my car and help people who were stranded (all bus and train services were halted). So, we need to learn to anticipate all these interruptions in service.

Since the 1989 quake, various San Francisco City Departments (such as the Fire Department ) have instituted the 72-hour rule. That is, we can not expect emergency services (police, fire, ambulance) within the first 72 hours after an earthquake. This means that we all need to be able to look after ourselves for the first 3 days. Basically, we have to learn to survive on our own without any utilities and medical assistance. The City of San Francisco has set up the website www.72hours.org in order to help educate its citizens about earthquake preparedness.

Being prepared is the key. We may not yet be able to predict exactly when earthquakes are going to occur, but we can prepare for them. The most important thing is to have a survival kit. This kit should contain water, solid/canned food, a “crank-up” radio and flashlight, first aid kit, blankets, raincoats, etc. The supply should be enough to last at least 3 days – even more so for distant areas. Be sure to have an emergency evacuation plan, and know how to contact relatives or meet up with them. Again, preparation is key. Being able to survive on our own during the first 72 hours is what we need to learn the most. Again, please visit www.72hours.com for more important information.

United States Geological Survey – www.usgs.gov Geology.com - www.geology.com National Earthquake Information Center –

www.earthquakes.usgs.gov Virtual Museum of the City of San Francisco – www.sfmuseum.org Disaster Resistant Berkeley Program – www.abag.ca.gov

www.ci.berkeley.ca.us The City of San Francisco 72-Hour Program – www.72hours.com Spyro Gyra – Baby Dreams Wells Fargo History Museum – www.wellsfargohistory.com Da Salas – Love and Support Wikipedia – www.en.wikipedia.org Foundations of Natural Science – Victor Maglambayan and Maria

Tejada You Tube – www.youtube.com