The modern man can get some solace from the fact that he is now able to understand some of the chief reasons responsible for an earthquake through research and scientific advancement. Earthquakes are no longer a sign of a divine wrath for him. He can now logically explain this strange phenomenon called an earthquake that boggled mankind for centuries. Post 1906 earthquake of San Francisco, man has learnt a lot about earthquakes.
An Earthquake is caused by a sudden release of enormous energy trapped beneath the earth crust that makes the underground tectonic plates grind past each other. The resulting friction causes a severe spurt of seismic waves that can displace the earth’s crust. If this sudden failure crosses a critical mark, the earthquake can cause widespread death and destruction through the displacement of the ground surface or even a tsunami. The boundary area where the tectonic plates strike against each other is known as the fault plane and the place where from the seismic waves emanate is known as the epicenter of the earthquake. The impact of the earthquake is felt the most over the area above or around the epicenter.
National Archives and Records Administration, 1906, The Ruins of San Francisco, Fig 1
The 1906 San Francisco Earthquake is also known as ‘the great San Francisco earthquake’. Although, more than a century has gone since it happened yet the harrowing memories of this earthquake linger on. It happens to be the worst natural disaster in the history of United States of America. The city of San Francisco has the dubious distinction of being precariously perched on the world’s biggest seismic Fault line named San Andreas.
San Francisco was rudely shaken by an earthquake measuring at least 7.7 to 8.25 at Richter scale at 5.12 A.M. on April 18, 1906. The epicenter of this earthquake was just two miles away from the city center of San Francisco near Mussel Rock. Massive in strength, this earthquake caused wide spread death and destruction. It also caused furious fires that raged for at least four days due to badly damaged and ruptured gas pipes. The resulting inferno devoured people and property alike.
The water pipes too gave way making water extremely scarce and almost unavailable. In the absence of water, it was almost impossible to control or douse the monstrous flames. The fire chief of San Francisco died due to mortal injuries incurred immediately after the earthquake leaving the fire department leaderless and waterless. Philip Fradkin, the author of ‘The Great Firestorms of 1906’ writes, "The firemen were virtually without water. There was very little to do. Now no fireman is going to do nothing. And the first idea that occurred was to use dynamite"1 to keep the fires from spreading. San Francisco was indeed caught unawares.
Berkley Seismological Lab, The Epicenter of 1906 San Francisco Earthquake, Fig 2
The enormity of this tragedy threw up several questions about America’s preparedness to face a natural disaster like this. The geologists in America had little knowledge about earthquakes and their origin at that period of time. The knowledge about tectonic plates was still at least half a century away. The 1906 San Francisco Earthquake indeed shook the American government out of its slumber and prompted it to initiate a much larger research on the factors that cause an earthquake.
Hence, the great earthquake of San Francisco marks the dawn of a great scientific revolution that would soon reveal the innermost dark secrets of the earth’s crust in the times to come. Elridge M. Moore writes, “The scientific inquiry conducted in the aftermath of the earthquake was among the world's earliest comprehensive postearthquake investigations and was the first conducted in the western United States”.2 It was the huge initiative taken by Professor Andrew C. Lawson, chairman, department of Geology, University of California that prompted the government to institute the Earthquake Investigation Commission.
Lawson was appointed the head of this commission consisting of several geologists handpicked from various reputed universities of America. The stage was now set for a full fledged investigation into the reasons that led to the great earthquake of San Francisco. The Lawson report of 1908 adequately armed America with much superior knowledge about earthquakes. It also enhanced awareness about the precautions that must be taken to save humanity from any such future disaster. The lessons learnt from1906 San Francisco Earthquake helped geologists like Reid to come out with an epoch-making theory like ‘the elastic-rebound theory’.
USGS, Reid's Elastic Rebound Theory, Fig 3
Till date, this theory is considered one of the best available explanations of the natural phenomenon that results in an earthquake. The wake up call issued by the San Francisco earthquake of 1906 made the geologists undertake massive research operations in the earthquake affected area. The research revealed the fact that the earthquake did maximum damage in the soft sedimentary soil areas of San Francisco. Rocky areas suffered less loss. The soft soil areas of San Francisco had as such experienced comparatively much greater amount of shaking and tremors. Whatsoever the scientists learnt from the study of the earthquake of 1906 now forms the basis of the modern study of seismology and earthquake science.
This information gathered by Lawson and his colleagues went a long way in properly distinguishing the areas which are specifically under the threat of an earthquake. The 1906 San Francisco Earthquake also led to a very significant method of observation known as triangulation surveys. This method revealed the vital fact that the impact of the earthquake was maximum near the fault line and it kept decreasing as one went farther away from it.
Actually Professor H.F. Reid based his world famous theory of elastic rebound on these very findings. Reid concluded that the crust of the earth keeps getting elastically distorted with the motion of tectonic plates over a large period of time. And, when it decides to revert back to its original position, it generates enormous seismic waves that cause earthquakes. Earthquake is thus a sudden release of previously stored energy under the crust of the earth. Moreover, it is the faulting that causes the earthquake and not the other way round.
The tremors of 1906 San Francisco Earthquake were felt right from Oregon to Los Angeles and beyond. In comparison, the 1989 earthquake of Loma Preita (greater San Francisco area) fades into insignificance as it had a rupture length of just 25 miles. The tremors of San Francisco earthquake were felt all along the San Andreas Fault line covering a distance of at least 296 miles. The great San Francisco Earthquake was so potent that the ground offset near Point Reyes went up to 20 feet, at the surface level. Down below,
Geology.Com, Map of San Andreas Fault Line, Fig 4
the offset was much larger and ranged up to 28 feet. The great earthquake lasted between 40-60 seconds and drastically changed the topography of San Francisco. The ground moved from under the feet of San Franciscans at a speed of approximately 4 to 5 feet per second whereas the rupture itself propagated at a speed of roughly 2.7 K.M. per second or 5800 miles per hour. The government initially tried to grossly downplay the ferocity of the earthquake by merely highlighting the role of fire in causing the immense loss.
The consideration behind such a false propaganda was to save the image of San Francisco as a very successful business center and California’s economic backbone. Fearing that the earthquake scare may not shoo away the investors from the city, the first public statement issued by the Governor of California read, “This is not the first time that San Francisco has been destroyed by fire, I have not the slightest doubt that the City by the Golden Gate will be speedily rebuilt, and will, almost before we know it, resume her former great activity."3 The fact that there is not even a mention of the earthquake in this statement says it all!
The financial loss caused by the earthquake of San Francisco was phenomenal. Keeping in view the value of the dollar in those days, the property loss suffered due to the earthquake was a staggering $400 million. More than 28000 buildings got destroyed due to the earthquake and fire. Before the earthquake of 1906, San Francisco was the hub of commercial activity in California. It was a kind of ‘Gateway to the Pacific’.
San Francisco’s success in the world of business and trade heralded its supremacy both in the Pacific and Asia. It was one of the busiest ports in United States of America. The 1906 San Francisco Earthquake and the resulting fire left almost 80 % of the city in ruins. The city did bounce back and rebuilt itself quickly but by that time the concentration of population and business had already shown a drift towards other cities like Los Angeles.
When the earthquake struck the trains tripped sideward, the buildings literally fell like a house of cards. The metalled roads got ripped apart like a piece of torn paper. The eyewitness accounts of the 1906 San Francisco Earthquake paint a horrific picture of the hell San Franciscans had to pass through. This is how an eyewitness named P. Barret described the terrible scene, “Then came the sickening swaying of the earth that threw us flat upon our faces. We struggled in the street. We could not get on our feet. Then it seemed as though my head were split with the roar that crashed into my ears. Big buildings were crumbling as one might crush a biscuit in one's hand. Ahead of me a great cornice crushed a man as if he were a maggot”.4 Another eyewitness saw the cobblestones flitting up and down like popcorn. Those who were on the top floors simply
USGS, 1906, 18 th Street near Folsom Street in San Francisco, Fig 5
stepped down on the ground floor as if in one big giant step. Those trapped within simply got squashed and crushed. Many died in their sleep or in the bed itself. Several got trapped in smoke and debris and were burnt alive. This indeed reminds one of Dante’s infernos.
The chaos and anarchy that followed the earthquake gave rise to acute law and order problem in the city. There were widespread reports of looting and arson around the San Francisco. Finding the situation going way out of hands the government virtually imposed an undeclared martial law on the city. More than 4000 federal troops landed on the streets of San Francisco. The Governor of California, George C. Pardee issued shoot at sight orders to stop the looting incidents.
The firemen and the soldiers started blowing up the buildings with gunpowder in order to create firebreaks. Fradkin points out, “One of the problems was the type of explosives that they used. Gunpowder is flammable and spreads fire. And they made the mistake on the end of the second day of dynamiting a huge chemical warehouse… and that was just pyrotechnics plus."5 Hence, the lack of experience and absence of any preparedness to face a natural calamity of this magnitude resulted in costly human errors. The rescue and relief operations miserably failed to deliver timely succor and proved to be counterproductive.
Many of those who survived the earthquake fell a helpless victim to the fury of fire. Similarly, many buildings that could withstand the earthquake got burned down by the blaze. Before the earthquake struck, San Francisco was home to more than 400,000 happy and prosperous people in 1906. The earthquake left about 3000 killed and more than 225,000 people homeless.
A letter written by a resident named Rosa Barreda lays bare the agony faced by the San Franciscans as an aftermath of the earthquake:
"Wednesday afternoon my Sister and I watched from the front bay window, second floor. Many burned-out people passed our house with huge bundles, and ropes around their necks dragging heavy trunks, if not huddled with baggage on wagons. From the moment they heard that fatal, heart-rending sound of the trumpet announcing their house would be burned or dynamited, they had to move on or be shot to death. As the sun set the black cloud we watched all day became glaringly red."6
The scene is indeed heart-rending! While the earthquake of 1906 laid bare the shoddy working of the government, it was also a witness to some real helping hand extended by one another. There were instances where several Italian residents offered the water they had saved for brewing wine at home or the wine itself from the wooden barrels to douse the flames in the neighborhood.
The Army played a laudable role in providing shelter, food and clothing to the refugees. The soldiers managed to control the incidents of arson and looting at an early stage, amidst the allegations that they mistakenly shot scores of innocent citizens too who were merely attempting to retrieve whatsoever belongings they could from fast approaching fire. Nevertheless, the army built several refugee camps for thousands of displaced San Franciscans. The people were largely grateful to the army for its yeoman’s service and support.
The enormity of the great earthquake of San Francisco can be measured from the fact that the seismographic center in Gottingen, Germany which is about nine thousand kilometers away from San Francisco very well experienced and recorded its seismic
USGS, 1906, San Francisco Earthquake - Compared to Loma Prieta, Fig 6
tremors. The graph in the figure clearly shows critical seismic tremors as represented by Compressional and Shear waves. The seismic graph of 1989 Loma Preita ( greater San Francisco) earthquake recorded at the same center in Germany, makes an interesting comparison. It clearly sets apart the vast difference between the intensity of the two earthquakes. The graph gives a unique insight into the fact that why the 1906 San Francisco Earthquake is called ‘the great earthquake of San Francisco’!
The fact is that San Francisco is sitting over a virtual time bomb. Its close proximity to San Andreas and several other fault lines like Hayward fault or Rodgers Creek fault makes it a fit candidate for another big earthquake in times to come. In spite of great technological strides that have been made by America in the world of earthquake monitoring, the reality is that nothing concrete can be done as yet to stop the reoccurrence of an earthquake like the great earthquake of 1906.
This reality must not be forgotten or ignored. The geologists fear the reoccurrence of such an earthquake somewhere in 2032. The scientific studies have also revealed that big earthquakes in the region are expected to occur at least once in every 200 years but nothing can be said for sure.
The fact that San Francisco was quickly rebuilt after the earthquake in order to reclaim its past glory and business, has its flip side too. The business community in tandem with the government went overboard to rebuild the city at a breakneck speed so as to enable it to host an international exposition in 1915. This led to a flagrant neglect of the desired building standards. The 1906 San Francisco Earthquake called for much stronger earthquake resistant structures.
The city blindly went ahead and built structures even weaker than 1906 standards. Risa A. Palm points out, “The vulnerability of buildings is a function not only of their location but also of their construction. Buildings constructed before 1940 are at greatest risk. Steinbrugge estimates that about 13 percent of all California structures are in this category.”7 It is only after 1940’s that San Francisco started building structures that are geared to face the prospect of another earthquake like the one seen in 1906.
Unfortunately, most of the pre 1940 buildings in San Francisco today will not be able to withstand even a much weaker earthquake than the earthquake of 1906. This fact alone is enough to send a shiver up the spine of a San Franciscan. Today, there are more than 1000 seismic centers spread across California minutely monitoring all sorts of seismic activities under the earth’s crust. The data is collected and processed with the help of computers and highly sophisticated instruments. In present times, the geologists have come a long way from the days of the great earthquake of 1906. They have been able to identify and zero down on hundreds of accompanying faults along the San Andreas Fault line that can cause earthquakes in the times to come.
The vigilance against earthquakes has increased manifold in the present time. A timely warning can certainly help mitigate the number of casualties. Had such defense preparedness been there in 1906, the losses would have been much less. No doubt, the 1906 San Francisco Earthquake left behind it a grim trail of death and destruction but it also brought about a realization that human life is a continuous challenge.
One must not give up in the face of such natural disasters rather one should gird up one’s loins to size up to any situation in life. Ignorance can cause great harm while awareness and knowledge can help us save our lives to a great extent. Knowledge is power and ignorance is death. No doubt, it is beyond human ken to stop the earthquakes but it is well within human reach to escape the fury of earthquakes through sagacity, precaution and proper preparedness.
Notes
1. Philip L.Fradkin, The Great Firestorms Of 1906 (University of California Press, 2005)
2. Elridge M. Moore and Dorothy L. Stout, Classic Cordilleran Concepts: A View from California , (Geological Society of America, 1999), 79.
3. George C. Pardee, “Get Busy”, The New San Francisco Magazine, May 1906,
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