Effects of earthquakes on humans and environment

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Effects of earthquakes on humans and environment

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Effects of earthquakes on humans and environment

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Earthquakes are among the most impressive geological processes with destructive effects on humans, nature and infrastructures. Secondary earthquake environmental effects (EEE) are induced by the ground shaking and are classified into ground cracks, slope movements, dust clouds, liquefactions, hydrological anomalies, tsunamis, trees shaking and jumping stones. Infectious diseases (ID) emerging during the post-earthquake period are considered as secondary earthquake effects on public health. This study involved an extensive and systematic literature review of 121 research publications related to the public health impact of 28 earthquakes from 1980 to 2015 with moment magnitude (Mw) from 6.1 to 9.2 and their secondary EEE including landslides, liquefaction and tsunamis generated in various tectonic environments (extensional, transform, compressional) around the world (21 events in Asia, 5 in America and one each in Oceania and Europe). The inclusion criteria were the literature type comprising journal articles and official reports, the natural disaster type including earthquakes and their secondary EEE (landslides, liquefaction, tsunamis), the population type including humans and the outcome measures characterized by disease incidence increase. The potential post-earthquake ID are classified into 14 groups including respiratory (detected after 15 of 28 earthquakes, 53.57%), water-borne (15, 53.57%), skin (8, 28.57%), vector-borne (8, 28.57%) wound-related (6, 21.43%), blood-borne (4, 14.29%), pulmonary (4, 14.29%), fecal-oral (3, 10.71%), food-borne (3, 10.71%), fungal (3, 10.71%), parasitic (3, 10.71%), eye (1, 3.57%), mite-borne (1, 3.57%) and soil-borne (1, 3.57%) infections. Based on age and genre data available for 15 earthquakes, the most vulnerable population groups are males, young children (age ≤ 10 years) and adults (age ≥ 65 years). Cholera, pneumonia and tetanus are the deadliest post-earthquake ID. The risk factors leading not only to disease emergence but also to disease incidence increase include (1) damage to infrastructures and health care systems that remained unfixed for a long time in the critical post-earthquake period, (2) aggravating weather conditions comprising immense and dramatic temperature changes, (3) prolonged physical exposure to large dust clouds generated by landslides and aspiration of contaminated tsunami water, (4) unfavorable conditions in overcrowded emergency shelters, (5) increased exposure to disease vectors population, (6) the weak immune system of elders, chronically ill individual and young children, (7) large percentage of illiteracy and population living below the national poverty line (insufficient personal hygiene), (8) poor education and training on disease prevention, (9) sanitary deficiencies, (10) lack of screening for blood-borne diseases before emergency surgeries, blood transfusions and intravascular drug use, (11) use of unsterilized medical equipment, (12) insufficient or low vaccination coverage and (13) close contact with the affected local population. In conclusion, our study referred to potential ID following strong, major and great earthquakes and their secondary EEE from 1980 to 2015. The establishment of a strong disaster preparedness plan following international guidelines and comprising adequate environmental and infrastructure planning and resilience of health facilities is fundamental for the enhancement of surveillance systems, the early detection of the emergence and spread of ID and their successful management.

Earthquake environmental effects are the effects caused by an earthquake, including surface faulting, tsunamis, soil liquefactions, ground resonance, landslides and ground failure, either directly linked to the earthquake source or provoked by the ground shaking.[1] These are common features produced both in the near and far fields, routinely recorded and surveyed in recent events, very often remembered in historical accounts and preserved in the stratigraphic record (paleo earthquakes). Both surface deformation and faulting and shaking-related geological effects (e.g., soil liquefaction, landslides) not only leave permanent imprints in the environment, but also dramatically affect human structures. Moreover, underwater fault ruptures and seismically-triggered landslides can generate tsunami waves.

EEE represent a significant source of hazard, especially (but not exclusively) during large earthquakes. This was observed for example during more or less catastrophic seismic events recently occurred in very different parts of the world.

Earthquake environmental effects are divided into two main types:

Effects of earthquakes on humans and environment

Coseismic surface faulting induced by the 1915 Fucino, Central Italy, earthquake

  1. Primary effects: which are the surface expression of the seismogenic source (e.g., surface faulting), normally observed for crustal earthquakes above a given magnitude threshold (typically Mw=5.5–6.0);

Effects of earthquakes on humans and environment

Coseismic liquefaction induced by one of the 2012 Emilia, Northern Italy, earthquakes

  1. Secondary effects: mostly this is the intensity of the ground shaking (e.g., landslides, liquefaction, etc.).

The importance of a tool to measure earthquake Intensity was already outlined early in the 1990s.[2] In 2007 the Environmental Seismic Intensity scale (ESI scale) was released, a new seismic intensity scale based only on the characteristics, size and areal distribution of earthquake environmental effects.

A huge amount of data about associated with modern, historical and paleoearthquakes worldwide, a infrastructure developed in the framework of the INQUA TERPRO Commission on Paleoseismology and Active Tectonics.

  • Earthquake light
  • Electromagnetic field
  • Richter magnitude scale

  1. ^ Michetti et al. (2007. Intensity Scale ESI 2007. In Memorie Descrittive Carta Geologica d’Italia L. Guerrieri and E. Vittori (Editors), APAT, Servizio Geologico d’Italia— Dipartimento Difesa del Suolo, Roma, Italy, 74, 53 pp.
  2. ^ Serva, L. (1994). The effects on the ground in the intensity scales, Terra Nova, 6, 414–416.

  • INQUA TERPRO Commission on Paleoseismology and Active Tectonics

Retrieved from "https://en.wikipedia.org/w/index.php?title=Earthquake_environmental_effects&oldid=1088662353"

Some of the common impacts of earthquakes include structural damage to buildings, fires, damage to bridges and highways, initiation of slope failures, liquefaction, and tsunami. The types of impacts depend to a large degree on where the earthquake is located: whether it is predominantly urban or rural, densely or sparsely populated, highly developed or underdeveloped, and of course on the ability of the infrastructure to withstand shaking.

As we’ve seen from the example of the 1985 Mexico earthquake, the geological foundations on which structures are built can have a significant impact on earthquake shaking. When an earthquake happens, the seismic waves produced have a wide range of frequencies. The energy of the higher frequency waves tends to be absorbed by solid rock, while the lower frequency waves (with periods slower than one second) pass through the solid rock without being absorbed, but are eventually absorbed and amplified by soft sediments. It is therefore very common to see much worse earthquake damage in areas underlain by soft sediments than in areas of solid rock. A good example of this is in the Oakland area near San Francisco, where parts of a two-layer highway built on soft sediments collapsed during the 1989 Loma Prieta earthquake (Figure 11.17).

Effects of earthquakes on humans and environment
Figure 11.17 A part of the Cypress Freeway in Oakland California that collapsed during the 1989 Loma Prieta earthquake. [from: http://upload.wikimedia.org/wikipedia/ commons/9/91/Cypress_collapsed.jpg]

Building damage is also greatest in areas of soft sediments, and multi-storey buildings tend to be more seriously damaged than smaller ones. Buildings can be designed to withstand most earthquakes, and this practice is increasingly applied in earthquake-prone regions. Turkey is one such region, and even though Turkey had a relatively strong building code in the 1990s, adherence to the code was poor, as builders did whatever they could to save costs, including using inappropriate materials in concrete and reducing the amount of steel reinforcing. The result was that there were over 17,000 deaths in the 1999 M7.6 Izmit earthquake (Figure 11.18). After two devastating earthquakes that year, Turkish authorities strengthened the building code further, but the new code has been applied only in a few regions, and enforcement of the code is still weak, as revealed by the amount of damage from a M7.1 earthquake in eastern Turkey in 2011.

Effects of earthquakes on humans and environment
Figure 11.18 Buildings damaged by the 1999 earthquake in the Izmit area, Turkey. [from U.S. Geological Survey at: http://gallery.usgs.gov/sets/1999_Izmit,_Turkey_Earthquake/thumb/_/1]

Fires are commonly associated with earthquakes because fuel pipelines rupture and electrical lines are damaged when the ground shakes (Figure 11.19). Most of the damage in the great 1906 San Francisco earthquake was caused by massive fires in the downtown area of the city (Figure 11.20). Some 25,000 buildings were destroyed by those fires, which were fuelled by broken gas pipes. Fighting the fires was difficult because water mains had also ruptured. The risk of fires can be reduced through P-wave early warning systems if utility operators can reduce pipeline pressure and close electrical circuits.

Effects of earthquakes on humans and environment
Figure 11.19 Some of the effects of the 2011 Tohoku earthquake in the Sendai area of Japan. An oil refinery is on fire, and a vast area has been flooded by a tsunami. [from: http://en.wikipedia.org/wiki/2011_T%C5%8Dhoku_earthquake_and_tsunami#/media/File:SH-60B_helicopter_flies_over_Sendai.jpg]
Effects of earthquakes on humans and environment
Figure 11.20 Fires in San Francisco following the 1906 earthquake. [from: http://upload.wikimedia.org/wikipedia/commons/3/3e/San_francisco_fire_1906.jpg]

Earthquakes are important triggers for failures on slopes that are already weak. An example is the Las Colinas slide in the city of Santa Tecla, El Salvador, which was triggered by a M7.6 offshore earthquake in January 2001 (Figure 11.21).

Effects of earthquakes on humans and environment
Figure 11.21 The Las Colinas debris flow at Santa Tecla (a suburb of the capital San Salvador) triggered by the January 2001 El Salvador earthquake. This is just one of many hundreds of slope failures that resulted from that earthquake. Over 500 people died in the area affected by this slide. [from: http://landslides.usgs.gov/learning/ images/foreign/ElSalvadorslide.jpg]

Ground shaking during an earthquake can be enough to weaken rock and unconsolidated materials to the point of failure, but in many cases the shaking also contributes to a process known as liquefaction, in which an otherwise solid body of sediment is transformed into a liquid mass that can flow. When water-saturated sediments are shaken, the grains become rearranged to the point where they are no longer supporting one another. Instead, the water between the grains is holding them apart and the material can flow. Liquefaction can lead to the collapse of buildings and other structures that might be otherwise undamaged. A good example is the collapse of apartment buildings during the 1964 Niigata earthquake (M7.6) in Japan (Figure 11.22). Liquefaction can also contribute to slope failures and to fountains of sandy mud (sand volcanoes) in areas where there is loose saturated sand beneath a layer of more cohesive clay.

Effects of earthquakes on humans and environment
Figure 11.22 Collapsed apartment buildings in the Niigata area of Japan. The material beneath the buildings was liquefied to varying degrees by the 1964 earthquake. http://en.wikipedia.org/wiki/1964_ Niigata_earthquake#/media/File: Liquefaction_at_Niigata.JPG

Parts of the Fraser River delta are prone to liquefaction-related damage because the region is characterized by a 2 m to 3 m thick layer of fluvial silt and clay over top of at least 10 m of water-saturated fluvial sand (Figure 11.23). Under these conditions, it can be expected that seismic shaking will be amplified and, the sandy sediments will liquefy. This could lead to subsidence and tilting of buildings, and to failure and sliding of the silt and clay layer. Current building-code regulations in the Fraser delta area require that measures be taken to strengthen the ground underneath multi-storey buildings prior to construction.

Effects of earthquakes on humans and environment
Figure 11.23 Recent unconsolidated sedimentary layers in the Fraser River delta area (top) and the potential consequences in the event of a damaging earthquake. [SE]

Exercise 11.4 Creating Liquefaction and Discovering the Harmonic Frequency

There are a few ways that you can demonstrate the process of liquefaction for yourself. The simplest is to go to a sandy beach (lake, ocean, or river) and find a place near the water’s edge where the sand is wet. This is best done with your shoes off, so let’s hope it’s not too cold! While standing in one place on a wet part of the beach, start moving your feet up and down at a frequency of about once per second. Within a few seconds the previously firm sand will start to lose strength, and you’ll gradually sink in up to your ankles.

If you can’t get to a beach, or if the weather isn’t cooperating, put some sand (sandbox sand will do) into a small container, saturate it with water, and then pour the excess water off. You can shake it gently to get the water to separate and then pour the excess water away, and you may have to do that more than once. Place a small rock on the surface of the sand; it should sit there for hours without sinking in. Now, holding the container in one hand gently thump the side or the bottom with your other hand, about twice a second. The rock should gradually sink in as the sand around it becomes liquefied.

Effects of earthquakes on humans and environment

As you were moving your feet up and down or thumping the pot, it’s likely that you soon discovered the most effective rate for getting the sand to liquefy; this would have been close to the natural harmonic frequency for that body of material. Stepping up and down as fast as you can (several times per second) on the wet beach would not have been effective, nor would you have achieved much by stepping once every several seconds. The body of sand vibrates most readily in response to shaking that is close to its natural harmonic frequency, and liquefaction is also most likely to occur at that frequency.

Earthquakes that take place beneath the ocean have the potential to generate tsunami.[footnote]Tsunami is the Japanese word for harbour wave. It is the same in both singular and plural.[/footnote] The most likely situation for a significant tsunami is a large (M7 or greater) subduction-related earthquake. As shown in Figure 11.24, during the time between earthquakes the overriding plate becomes distorted by elastic deformation; it is squeezed laterally (Figure 11.24B) and pushed up.

When an earthquake happens (Figure 11.24C), the plate rebounds and there is both uplift and subsidence on the sea floor, in some cases by as much as several metres vertically over an area of thousands of square kilometres. This vertical motion is transmitted through the water column where it generates a wave that then spreads across the ocean.

Effects of earthquakes on humans and environment
Figure 11.24 Elastic deformation and rebound of overriding plate at a subduction setting (B). The release of the locked zone during an earthquake (C) results in both uplift and subsidence on the sea floor, and this is transmitted to the water overhead, resulting in a tsunami. [SE]

Subduction earthquakes with magnitude less than 7 do not typically generate significant tsunami because the amount of vertical displacement of the sea floor is minimal. Sea-floor transform earthquakes, even large ones (M7 to M8), don’t typically generate tsunami either, because the motion is mostly side to side, not vertical.

Tsunami waves travel at velocities of several hundred kilometres per hour and easily make it to the far side of an ocean in about the same time as a passenger jet. The simulated one shown in Figure 11.25 is similar to that created by the 1700 Cascadia earthquake off the coast of British Columbia, Washington, and Oregon, which was recorded in Japan nine hours later.

Effects of earthquakes on humans and environment
Figure 11.25 Model of the tsunami from the 1700 Cascadia earthquake (~M9) showing open-ocean wave heights (colours) and travel time contours. Tsunami wave amplitudes typically increase in shallow water. [from NOAA/PMEL/Center for Tsunami Research, at: http://nctr.pmel.noaa.gov/cascadia_simulated/]

Tsunami are discussed further in Chapter 17 under the topic of waves and coasts.