Book summary “Earthquakes in Human History”: summary

Introduction

You live on a dynamic planet where sudden geological shifts routinely alter the course of human civilization. When the ground ruptures beneath your feet, the resulting catastrophe extends far beyond physical destruction into the realms of religion, politics, and philosophy.

Earthquakes are not merely destructive geological events but powerful catalysts that profoundly shape human history, religion, politics, and culture.

Jelle Zeilinga de Boer examines how seismic hazards operate across different tectonic settings and influence societies from antiquity to the modern era. You will explore the physical mechanisms of faults alongside the profound social aftereffects of historical tremors.

Consider these questions as you read:

• How do tectonic plates generate seismic waves that transform human landscapes?
• What role did ancient rifts play in biblical catastrophes?
• How did the Lisbon disaster spark the birth of modern seismology and shift Enlightenment thought?
• What lessons do intense subduction zones hold for future architectural engineering and disaster preparedness?

1. Geological Origins and Seismic Measurement

Tectonic plate movements generate seismic waves that are measured through qualitative and quantitative scales.

Plate Tectonics Mechanism

The lithosphere consists of rigid plates made of crust and uppermost mantle material moving over the weak asthenosphere due to convection currents. When these plates separate, collide, or slide laterally past one another, stress accumulates until friction is overcome and rocks rupture.

The Mino-Owari earthquake in Japan created a fault scarp several meters high across Honshu in 1891, demonstrating the causal relationship between faulting and earthquakes. Geologists came to understand plate tectonics in the 1960s.

Seismic Waves and Measurement

Rupturing originates at the focus, with the epicenter directly above it on the surface. P-waves and S-waves travel through the body of the earth, while Rayleigh and Love waves travel along the surface, causing the most damage. S waves travel at a typical speed of 3 kilometers per second in midcrustal rocks, while P waves reach 5 kilometers per second.

Intensity is measured using the modified Mercalli scale, while magnitude is quantified using logarithmic scales where energy increases drastically per unit. Giuseppe Mercalli developed his scale with 12 degrees of intensity in 1902. Charles Richter developed his quantitative magnitude scale in 1935 at the California Institute of Technology, where energy release is 30 to 40 times greater from one Richter magnitude to the next.

Ground shaking intensity is heavily influenced by local geological conditions, and secondary hazards like fires and tsunamis often cause more destruction than the initial quake. Seismic waves are amplified in unconsolidated sediments and marshes compared to hard bedrock. Furthermore, broken utilities ignite massive fires in cities, seafloor displacement creates destructive tsunamis, and mountainous regions suffer from severe landslides. San Francisco in 1906 and Tokyo and Yokohama in 1923 suffered powerful earthquakes, but conflagrations completed the destruction.

Human activities such as filling large reservoirs and injecting waste fluids into deep wells can induce earthquakes by lubricating faults and reducing friction. High-pressure fluids injected into deep wells penetrate old fracture zones, reducing frictional resistance along inactive fault planes and triggering slippage. Similarly, the immense weight of water behind massive dams can strain the earth's crust and reactivate faults.

The Hoover Dam was built in the 1930s, and filling Lake Mead produced an earthquake near Las Vegas with a magnitude of 5. The Aswan Dam was built in Egypt in 1970, with a height of 100 meters, a width of 3 kilometers, and Lake Nasser reaching a length of 350 kilometers, leading to a 5.6 magnitude earthquake near the lake on November 14, 1981. After the Koyna Dam was built, an induced quake of magnitude 6.4 killed several hundred people. At the U.S. Army's Rocky Mountain Arsenal near Denver, Colorado, a 3 kilometers deep disposal hole was drilled in 1962 to dispose of liquefied nerve gas. Deep-well disposal caused earthquakes that stopped when pumping was discontinued, which David Evans explained using a water-filled beer can model, culminating in a 4.3 magnitude tremor in late April.

2. Biblical Catastrophes and Ancient Rifts

Active tectonic faults in the Middle East fueled historical disasters and shaped ancient civilizations.

The Dead Sea rift is a major tectonic fault zone formed by the northward movement of the Arabian platelet relative to the Palestinian platelet. The Arabian platelet separated from the African plate 34 million years ago and drifts northward, creating a fault zone up to 20 kilometers wide and over 1,000 kilometers long. Rock units east of the rift have moved more than 100 kilometers farther north than those on the west, with an average relative movement rate of 1.7 centimeters a year.

Massive underground salt deposits in the Dead Sea basin have been forced upward through weak zones by overlying sediment weight, creating salt domes like Mount Sedom. Ductile rock salt behaves similarly to toothpaste squeezed from a tube when compressed by thick clastic sediments. Weathering and erosion of these salt structures over time produce unique columns and shapes, which locally inspired legends such as Lot's wife.

On the eastern flank of Mount Sedom, a prominent column of rock salt is known locally as Lot's wife, with other groups referred to as Lot's harem. The southern Dead Sea basin southern oil drilling reveals an 8 kilometers thickness of sediments, while 10 million tons of salt precipitate out of the waters every year.

Dead Sea Rift Tectonics

Faults penetrating oil-bearing deposits in the Dead Sea region cause petroleum and asphalt to seep to the surface, creating historical tar pits. Ancient writers frequently documented asphalt and bitumen bubbling up from the Dead Sea during tectonic activity. These floating asphalt blocks and tar pits were harvested for construction mortar, boat caulking, and mummification in Egypt.

The Roman commander Titus threw chained slaves into the Dead Sea, but because of the extreme water salinity and buoyancy, they floated back to shore and were pardoned. The current surface of the Dead Sea sits at 390 meters below sea level, while the deepest part reaches 730 meters below sea level.

Sodom and Jericho

The legendary destruction of Sodom and Gomorrah around 2100 BCE was likely caused by a major earthquake that ignited petroleum and gas reserves along fault lines. Earthquakes release immense friction heat capable of melting rock and igniting hydrocarbon gases and petroleum seeping from fault fissures. This mechanism provides a scientific explanation for the biblical account of brimstone, fire, and smoke raining down upon the plain.

Geologist B. K. Emerson suggested in 1896 that fault movements in petroleum-rich areas caused spontaneous combustion, a phenomenon supported by nineteenth-century accounts of ignited seeps during California earthquakes like the 7.8 magnitude 1857 Fort Tejon earthquake.

The ancient fortifications of Jericho were repeatedly destroyed throughout history by severe earthquakes along the active local fault zone. Jericho relies on a dependable freshwater spring emerging from the Jericho fault. Because the region is tectonically unstable, severe earthquakes frequently breached fortified mud-brick walls and disrupted water sources, facilitating conquests by outside groups.

Joshua's conquest of Jericho around 1300 or 1315 BCE and the miraculous halting of the Jordan River flow likely coincided with earthquake-induced landslides that temporarily dammed the river. The bottom layer of Jericho dates back to the 7th millennium BCE, with an estimated early population of 2,000 people, 4 meters height of Bronze Age walls, and 7 meters width of the city watchtower walls.

A powerful earthquake in 31 BCE caused severe destruction across Judea and influenced military maneuvers during the war between Mark Antony and Octavian. The seismic event damaged Jerusalem's temple, Herod's palace in Jericho, and the fortifications at Masada located 50 kilometers from Jerusalem. King Herod used the psychological impact of the disaster to rally his dispirited troops and successfully defeat the invading Arab army during the year of the major Judean earthquake and the Battle of Actium.

3. Greek Collisions and British Tremors

Intraplate stresses and plate subduction zones dictate seismic hazards from Greece to Great Britain.

Greece experiences frequent earthquakes because it lies in a collision zone where tectonic plates are driving regional uplift and fracturing ancient sea floors. The African plate is subducting beneath the Eurasian plate while the Arabian platelet pushes the Anatolian platelet westward like a bulldozer, driving the Aegean region southwest and uplifting overlapping slabs of limestone, marble, and volcanic rock. The resulting stress creates nearly vertical faults along the flanks of mountain ranges such as Pylos, Taygetos, and Parnon in the Peloponnesus. The Pylos Mountains stand approximately 1,000 meters above sea level, the Taygetos range reaches roughly 2,500 meters, and the Parnon range attains 2,000 meters.

Spartan Earthquake

A devastating earthquake in 464 BCE triggered the gradual political decline of Sparta by decimating its population and inciting a massive helot rebellion. The earthquake originated on a shallow fault along the Taygetos Mountains with an estimated magnitude of 7.2, destroying stone buildings throughout Sparta, causing massive rockfalls, and killing thousands of soldiers, women, and children, which severely limited future military replacements. The focal depth was estimated at 5 kilometers, and a fault scarp reaching a maximum height of 12 meters formed west of Sparta. The recurrence interval for strong quakes on the Spartan fault is approximately 3,000 years.

Historian Diodorus Siculus recorded that over twenty thousand Lacedaemonians perished, and Plutarch noted that mountain peaks on Taygetus fell and all of Sparta except five houses was shattered.

Ancient Greek philosophers, particularly Aristotle, theorized that earthquakes were caused by subterranean winds generated by heat acting on underground moisture. Rejecting earlier hypotheses by Anaximenes, Anaxagoras, and Democritus involving collapsing hollows, flat earth air-traps, or excess rainwater, Aristotle argued that solar and internal heat generated underground winds that circulated and caused tremors similar to bodily spasms. Aristotle, whose lifespan spanned from 384 to 322 BCE, wrote in Meteorologica that sound precedes an earthquake because sound waves are finer and more penetrating than wind. He noted that severe earthquake shocks and subsequent symptoms can sometimes continue for forty days.

London Panics

Great Britain experiences earthquakes despite being safely situated far from active plate boundaries due to internal crustal stresses released along ancient faults. British earthquakes are caused by movement along fractures well within the Eurasian plate, particularly concentrated in Scotland, northern and western England, and the southeastern Artois fault zone extending beneath the English Channel into France and Belgium. Britain sits 1,000 kilometers away from the nearest active collision zone in the Alps, yet England has recorded a minimum of 500 temblors since the tenth century. The Artois fault zone generates horizontal compressional forces that thrust one crustal segment over another, leading to recorded historical earthquakes.

In medieval and early modern England, religious authorities consistently interpreted earthquakes as direct manifestations of divine wrath meant to punish sinners and warn the impenitent. Before modern scientific understanding emerged, churchmen and pamphleteers argued that attributing earthquakes purely to natural subterranean vapors ignored God's active moral judgment and call for repentance. During the 1382 earthquake council examining John Wycliffe for heresy at Blackfriars monastery, participants panicked, though the archbishop cleverly used the tremor to argue that purging wicked individuals would end community convulsions. The 1382 earthquake had an estimated magnitude of 5.7 and caused a tremor lasting approximately 30 seconds in Kent.

A cluster of earthquakes in London in the year 1750 provoked widespread panic, mass evacuations, and intense religious revivalism led by early Methodists. Following ominous signs including a red aurora borealis and a violent storm in Bristol, minor shallow earthquakes struck London exactly a month apart in February and March, prompting military men and pamphleteers to predict a catastrophic third shock. The February 8, 1750 London earthquake had an estimated magnitude of 2.6, while the March 8 earthquake measured about 3. Stephen Hales noted that the March earthquake lasted approximately four seconds. Fearing divine judgment, approximately one hundred thousand people fled London in early April to sleep in the open fields or stay in outlying towns until the panic subsided.

4. The Lisbon Earthquake and Enlightenment

The 1755 Lisbon disaster shattered European optimism and gave birth to modern seismology.

Lisbon 1755 Impact

The catastrophic Lisbon earthquake of November 1, 1755, destroyed the Portuguese capital and triggered philosophical and scientific revolutions across Europe. The quake caused widespread destruction through shaking, fires, and tsunamis, prompting intellectuals to question the prevailing religious dogmas of divine wrath and the philosophical doctrine of optimism.

On All Saints' Day, massive crowds gathered in Lisbon churches; as roofs collapsed, fires broke out from cooking hearths, and tsunamis up to 10 meters high struck the coast. The disaster resulted in an estimated 10,000 people killed outright in Lisbon, while 20,000 houses were consumed by fires.

Minister Sebastiao José de Carvalho e Mello, later known as the Marquês de Pombal, used the Lisbon disaster to exert dictatorial control, rebuild the city, and curb the power of the church and nobility. Pombal had the dead buried at sea to prevent plague, established food distribution centers, and ultimately exiled the Jesuits after a royal assassination attempt.

Optimism versus Voltaire

The Lisbon earthquake shattered the eighteenth-century optimism championed by Leibniz and Pope, inspiring Voltaire to critique the notion of universal good. While philosophers like Rousseau argued that human misery stemmed from abandoning nature and crowding into cities, Voltaire used poetry and satire to expose gratuitous evil. Voltaire published the satirical work Candide in 1759, ridiculing blind optimism through the character Pangloss.

Geologist John Michell laid the groundwork for seismology by proposing a method to locate earthquake epicenters using wave propagation directions. By plotting wave direction lines on a map and extending them until they intersected, Michell confirmed that the 1755 Lisbon earthquake originated in the eastern Atlantic. You can apply his method with these steps:

• Plot the directions of wave propagation at different locations as lines on a map.
• Extend the lines until they intersect to find the earthquake origin.

The 1755 Lisbon earthquake resulted from tectonic compression and fault rupturing along the active boundary between the Eurasian and African plates. Differential movement and counterclockwise rotation of the African plate caused crustal extension in the Azores and compression off the coast of Portugal, uplifting features like the Gorringe Bank and the Pombal fault.

5. New Madrid and San Francisco

Intracontinental quakes and coastal fault ruptures demonstrate the extreme danger of soil liquefaction and fires.

New Madrid Liquefaction

The New Madrid earthquakes caused widespread liquefaction of water-soaked sediments, erupting into sand blows and forming topographic depressions known as sunk lands. Shaking liquefied underground lenses of sand containing groundwater, forcing the sandy liquid upward through fissures. The surface eruptions created cratered mounds called sand blows, while the compaction of unconsolidated sediments caused regional subsidence, creating sunk lands like Reelfoot Lake.

Explorer Louis Bringier described craters up to 30 meters across and a meter high, while fur trapper A.N. Dillard noted large trees submerged 3 to 6 meters beneath water in the newly formed sunken lands. A belt of liquefaction and sand blows spanned 80 kilometers wide and 210 kilometers long.

The 1811-1812 earthquakes severely disrupted the Mississippi River by causing massive bank failures, choking the channel with debris, and temporarily reversing its current. Fissures opened in the riverbed and natural levees, causing massive forested sections of the banks to slump into the stream. Upthrusting of the riverbed created rapids that momentarily forced the current to flow backward.

Eyewitness Eliza Bryan described the river receding, then returning as a perpendicular wall of water 15 to 20 feet high that tore boats from their moorings. The river level rose 5 or 6 feet following temporary checks to the current.

Congressional relief for victims of the New Madrid earthquakes ultimately devolved into widespread land speculation and fraud. Congress passed a law allowing victims whose land was destroyed to claim an equal area of public land elsewhere. Because many victims did not want to move, they sold their claim certificates cheaply to speculators, leading to rampant forgery. The U.S. Supreme Court spent years trying to untangle the resulting legal mess where the term New Madrid claim became synonymous with fraud.

The religious and military alliance led by Tecumseh and his brother Tenskwatawa among Native American tribes was fueled by spiritual revival and prophecies tied to natural portents. Tenskwatawa gained immense following after a near-death revival, preaching a return to traditional ways. Tecumseh translated this religious movement into a political and military alliance to stop white encroachment, linking his warnings to environmental phenomena like floods, comets, and earthquakes.

Tenskwatawa successfully predicted a solar eclipse on June 16, 1806, after being challenged by Indiana Governor William Henry Harrison, greatly increasing his prophetic influence. The Methodist Church gained 15,000 converts within the earthquake-affected region.

San Francisco 1906

While the 1906 earthquake caused significant structural damage in San Francisco, the ensuing unchecked fires caused the vast majority of the city's destruction.

The 1906 San Francisco earthquake was caused by the abrupt release of tectonic stress along a massive rupture of the San Andreas fault. A 470-kilometer stretch of the San Andreas fault ruptured at an estimated velocity of 3 kilometers per second, generating an earthquake with a magnitude of about 8. The epicenter lay 15 kilometers southwest of San Francisco in the ocean.

Steamers like the Argo and the schooner John A. Campbell felt sharp tremors at sea as if they had struck reefs or derelicts, encountering shock waves radiating from the fault.

The earthquake broke most of San Francisco's water mains, leaving firefighters with little or no water pressure. Combined with pre-existing political corruption, neglected cisterns, and a lack of auxiliary saltwater infrastructure, scattered fires coalesced into a massive three-day conflagration. Fire Chief Dennis Sullivan was mortally injured when a chimney crashed through his firehouse floor during the initial earthquake, depriving the department of crucial leadership.

The raging fires burned for three days across 10 square kilometers where virtually every building was destroyed, leaving 250,000 people homeless.

6. Japanese Subduction and Preparedness

The Japanese islands experience frequent earthquakes and volcanic activity because they lie within a complex tectonic zone where multiple plates are colliding and subducting. The Pacific and Philippine plates are being subducted beneath the Eurasian plate along deep ocean trenches, creating intense crustal stresses that are higher in the northern arc due to faster subduction rates. The Philippine plate is being subducted northwestward at about 4 centimeters a year, while the Pacific plate is subducting at about 10 centimeters a year.

Complex subduction zones drive intense Japanese seismicity, demanding rigorous architectural engineering and preparedness.

Great Kanto Earthquake

The 1923 Great Kanto Earthquake in Japan caused unprecedented destruction primarily due to wind-driven firestorms that swept through densely populated wooden urban areas. The quake struck during lunchtime when millions of households were using open charcoal fires for cooking, which were scattered by tremors and fanned into firestorms by a passing typhoon.

At a 6-hectare site at an army clothing depot on the Sumida River, a fire tornado trapped and burned to death approximately forty thousand refugees. The Kanto Dai-shinsai left 150,000 people dead after an estimated 8.3 magnitude tremor turned 18 square kilometers to ashes in Tokyo.

Engineering Solutions

Thoughtful architectural engineering can successfully protect buildings from severe earthquake damage on soft, unconsolidated soil. Architect Frank Lloyd Wright floated a large hotel structure on concrete piles driven deep into mud, reinforced walls with steel, and segmented the building into discrete sections to move independently during a quake.

During the 1923 Kanto earthquake, the newly opened Imperial Hotel in Tokyo survived with little damage while surrounding masonry structures collapsed across the 18 meters deep soft sediment layer.

In response to historical catastrophes, Japan has established systematic national preparedness measures, including mandated engineering codes, evacuation protocols, and annual drills. The government enforces strict building safety standards and maintains designated open evacuation sites, while conducting nationwide exercises on the anniversary of the Kanto disaster.

You can follow these systematic practices:

• Conduct annual earthquake drills in schools and offices on September 1.
• Store emergency supplies including food and blankets at strategic urban locations.
• Mark streets leading to designated parks and open areas clearly for evacuation.

Conclusion

Earthquakes reveal the intimate connection between deep Earth dynamics and human history. You can see how tectonic movements dictate not only physical destruction but also religious beliefs, political structures, and scientific revolutions across the globe. Understanding this seismic reality helps you prepare for inevitable natural hazards.

1. Assess your local seismic risk based on proximity to active plate boundaries or intraplate fault zones.
2. Retrofit your home and workplace to withstand ground shaking and prevent structural collapse.
3. Secure heavy furniture, appliances, and utility lines to minimize injuries during tremors.
4. Prepare an emergency supply kit with water, food, and medical supplies for the aftermath of a disaster.
5. Practice drop, cover, and hold on procedures to protect yourself instantly when ground motion begins.

10 Key Ideas

1. Tectonic plate movements generate seismic waves that are measured through qualitative and quantitative scales.
2. Active tectonic faults in the Middle East fueled historical disasters and shaped ancient civilizations.
3. Intraplate stresses and plate subduction zones dictate seismic hazards from Greece to Great Britain.
4. The 1755 Lisbon disaster shattered European optimism and gave birth to modern seismology.
5. Intracontinental quakes and coastal fault ruptures demonstrate the extreme danger of soil liquefaction and fires.
6. While the 1906 earthquake caused significant structural damage in San Francisco, the ensuing unchecked fires caused the vast majority of the city's destruction.
7. Complex subduction zones drive intense Japanese seismicity, demanding rigorous architectural engineering and preparedness.
8. Assess your local seismic risk based on proximity to active plate boundaries or intraplate fault zones.
9. Retrofit your home and workplace to withstand ground shaking and prevent structural collapse.
10. Prepare an emergency supply kit with water, food, and medical supplies for the aftermath of a disaster.