1917–1918 earthquakes

1917–1918 earthquakes
Name	1917–1918 seismic sequence
Years	1917–1918
Affected	Eurasia; North America; Caribbean
Magnitude	Various (up to ~7.8)
Depth	Shallow to intermediate
Casualties	Tens of thousands (est.)
Intensity	VIII–X (MMI)

1917–1918 earthquakes were a series of seismic events occurring during 1917 and 1918 that affected multiple regions across the globe, producing widespread destruction, social disruption, and renewed interest in seismological research. The sequence coincided with major contemporary events such as World War I, the Russian Revolution, and the Spanish flu pandemic, complicating relief and reconstruction. Contemporary observers included scientists associated with institutions like the United States Geological Survey, the British Geological Survey, and the Imperial Geophysical Laboratory.

Background and tectonic setting

The seismicity of 1917–1918 occurred along several tectonic regimes including the Alpine orogeny system, the San Andreas Fault transform zone, and subduction zones related to the Cocos Plate and the Nazca Plate. In Eurasia, interactions between the Eurasian Plate and the Indian Plate influenced rupture propagation near the Himalayas and the Caucasus, while in the Caribbean the dynamics of the Caribbean Plate and the North American Plate governed events near Hispaniola and Puerto Rico. Geologists referenced the work of figures such as Alfred Wegener and institutions like the Royal Society when interpreting crustal deformation, and compared mechanisms to earlier earthquakes like the 1906 San Francisco earthquake and the 1908 Messina earthquake. Paleoseismology and mapping by agencies including the Geological Survey of Canada and the Institut de Physique du Globe de Paris later helped contextualize the 1917–1918 ruptures.

Major earthquakes and chronology (1917–1918)

Chronology lists prominent events that drew international attention. Notable shocks included a large event in early 1917 near the Azores Triple Junction, a mid-1917 earthquake affecting the Anatolian Fault region proximate to Istanbul, a late-1917 rupture along the San Andreas Fault system impacting California communities, and a powerful 1918 subduction-related quake off the coast of Chile near the Atacama Desert. Each event was reported by newspapers like The Times and scientific bulletins from the US National Research Council. Seismographs at observatories such as the Kew Observatory, the Göttingen Observatory, and the Tokyo Imperial University recorded differing waveforms, and catalogues compiled by the International Seismological Association attempted to standardize magnitudes against the Richter magnitude scale precursors and intensity scales from the Mercalli intensity scale.

Impact and casualties

Casualty estimates varied with location and contemporaneous reporting. Urban centers including San Francisco, Istanbul, Valparaíso, and ports in the Levant experienced fatalities and injuries, while rural districts in the Caucasus and Andes reported higher mortality from landslides and aftershocks. Disruption coincided with troop movements tied to Gallipoli campaign aftermaths and refugee flows from the Ottoman Empire territories, and medical response was constrained by outbreaks such as those recorded by World Health Organization predecessors and field hospitals operated by organizations like the American Red Cross and Red Crescent societies. Demographers from institutions like the London School of Hygiene & Tropical Medicine later incorporated the events into mortality reconstructions for 1917–1918.

Damage to infrastructure and cultural heritage

Damage encompassed railways like the Trans-Siberian Railway, ports including Valparaíso, bridges such as those on the Bosporus approaches, and industrial installations near San Pedro and Penco. Heritage losses affected monuments and religious sites including churches in Constantinople and colonial-era buildings in Havana and Kingston, Jamaica. Hospitals, schools affiliated with universities like Harvard University and University of Oxford saw structural impairments, and archives in institutions such as the Vatican Archives and regional museums reported damage to collections. Shipping lanes and telegraph networks maintained by companies like the Marconi Company experienced interruptions, complicating communication among relief organizations including the International Committee of the Red Cross.

Response, relief efforts, and reconstruction

Immediate relief involved municipal authorities in cities like Los Angeles, Buenos Aires, and Alexandria coordinating with national bodies such as the U.S. Army Corps of Engineers and colonial administrations in British India and French Indochina. Philanthropic organizations including the Salvation Army and mission societies from Princeton University and Yale University mobilized aid, while reconstruction drew on engineering practices from firms associated with the Royal Engineers and the Great Northern Railway. Reconstruction programs in Chile referenced international lenders including banks based in London and New York City, with architects influenced by proponents like Le Corbusier later arguing for seismic-resilient design informed by the devastation. Legal frameworks for building codes evolved, taking cues from precedents like ordinances implemented after the 1906 San Francisco earthquake.

Scientific studies and seismological analysis

Seismologists such as Beno Gutenberg and contemporaries at the International Seismological Centre analyzed waveforms from 1917–1918 using early seismometers produced by firms like the Galitzin apparatus manufacturers and laboratory setups at the Uppsala University. Studies compared focal mechanisms to historic ruptures catalogued by the Geological Society of America and debated stress transfer theories later formalized in works by researchers at the Scripps Institution of Oceanography and the Institut de Physique du Globe de Paris. The events stimulated advances in macroseismic atlas compilation, prompted enhancements to tsunami warning considerations by agencies such as the Hydrographic Office and influenced the later development of seismic zoning maps used by national bodies like the Federal Emergency Management Agency's predecessors. Subsequent paleoseismic investigations referenced trenching studies near the San Andreas Fault and stratigraphic analyses in the Andes to place 1917–1918 into longer-term recurrence models.

Category:Earthquakes by year