Tectonic activity and hazardsExplore the causes of different types of tectonic hazards and spectrum of

responses to them.

Research a range of examples of different hazard events and the reasons why responses to them differ.

Define – tectonic hazard, hazard

Causes Of different types of tectonic hazard

- Diff lava type – andesitic , rhyolitic- Plate margins- VEI...page 14- Hazard profile

Responses

Spectrum – do noting – change the event, modify , modify vulnerability

Why are responses different

- Various players -

Pakistan

Caliufornia

Depends on vulnerability

Nature of hazard

Level of development

Education

Case study nevado del ruiz

California

Kashmir

Mt merapi

montserrat

• Tectonic activity can produce a very large range of hazard events

• Not all of these events are ‘disasters’

• A natural hazard event becomes a disaster when the event causes a significant impact on a vulnerable population.

• These impacts could be human (death, injury) and / or economic (property losses, loss of income).

Definitions vary, but ‘significant’ losses usually means 10+ deaths / 100+ affected / $1 million losses

• The range of volcanic hazards

• Tectonic processes are driven by radioactive decay in the core

• This decay generates heat inside the earth, which drives vast convection currents

• This convection is largely responsible for plate movement

•

• Most tectonic hazards are concentrated at plate margins (boundaries), although ‘hotspots’ are a notable exception.

• Different types of boundary generate very different tectonic hazards.

• Dangerous volcanic hazards are found along subduction zones at destructive plate margins

• The most dangerous volcanoes are themselves multiple hazard areas.

• Volcanoes at constructive plate margins (Iceland) and oceanic hotspots(Hawaii) are much less hazardous and destructive.

Magma generation

• Magma, molten rock in the earth’s crust, has an important relationship with volcanic explosivity and hazard level

Magma

type

Generation Tectonic setting Hazards

Basaltic

Low silica, low gas, low viscosity.

Dry partial melting of upper mantle

Oceanic Hot spot (Hawaii)

Constructive (Iceland)

Lava flow

Andesitic

Intermediate

Wet partial melting of subducting plates

Destructive plate margin (Andes)

Island arc margin (Montserrat)

Lava flow, ash and tephra, pyroclastic flow, lahar, gas emission

Rhyolitic

High silica, high gas, high viscosity.

In situ melting of lower continental crust

(very rare eruptions)

Continental Hot spot (Yellowstone)

Continent collision zone (Himalayas)

Cataclysmic explosion, pyroclastic flow

• Andesitic magmas, formed by wet partial melting at subduction zones produce highly explosive and destructive composite volcanoes

Measuring volcanic explosivity: (diagram)

• The Volcanic Explosivity Index (VEI) is used to measure volcanic power.

• VEI measures: Volume of ejecta Height of the eruption column Duration of the eruption.

• Modern humans have never experienced a VEI 7 or 8

• Magma type and volcano morphology

• Volcanoes are extrusive igneous landforms. The form of volcanoes is related to magma types, and therefore to different tectonic settings:

• Basaltic – huge, low relief shield volcanoes plus small scoria cones and fissure vents.

• Andesitic – steep sided strato-volcanoes; layers of lava, ash and tephra.

• Rhyolitic – central craters with lava plugs / domes, due to high viscosity of the lava. Calderas and collapse calderas.

• 4. Response to tectonic hazards

• People cope with natural hazards in very different ways

• The chosen ways are often related to wealth and access to technology

• Humans do have a capacity to ignore or seriously underestimate risk, even when it seems obvious to others

• Often it may seem obvious that people should move out of harms way, but in reality this may be impossible.

•

• Hazard modification

• Several different approaches can be taken to reduce the impacts of tectonic hazards:

•

• The hazard management cycle

• Successful hazard management involves a cycle (see diagram) which focuses on the 3 types of modification from the previous slide.

• A focus on modifying loss only, will not improve survival chances when the next hazard strikes

• Long before a natural hazard event, there needs to be a focus on mitigation and prevention (if possible) as well as human preparedness.

•

Type of event

Earthquake

Modify the event

Rangely, Colorado• Rangely is an active oil field. Water was being pumped into the ground 10,000,000 gallons per day. Injected into rocks 6,000 feet below the surface

Water flushes oil from the pore spaces and opens channels along which the oil can move. Oil company geologists had good data on pumping volume and the fluid pressure. It would be easy to monitor changes in fluid pressure and earthquake frequency

The experiment workedRaising pore pressure triggered earthquakes. Reducing pore pressure turned them offTherefore, by monitoring fluid pressure, it was even possible to predict the size of earthquakes that would be producedThis method could be used to control earthquakes on the San Andreas

AnalysisThis method is ingenious but it has its costs. Seventy weels need to be built 5 km deep and 5km apart. Drilling costs ~$100/foot x 17,000 ft per wellIt would cost $120,000,000 just to drillTotal cost is high and will be hard to sellPumping needs to be repeated every six monthsIt is riskyIt may take a prohibitively large number of small earthquakes to prevent a big one

Modify the Vulnerability

Vulnerability can be reduced by earthquake- proofing buildings and infrastructure. Remote sensing by satellitie has been used to view small crust movements that occur during earthquakes. After the Kobe earthquake in Japan (1995), the National Research Institue for Earth Science and Disaster Prevention (NIED) deployed 1000 strong motion accelerometers throughout the country. This is called the Kyoshin Network. During an earthquake, primary and secondary wave velocities are measured at each site and logged. Data are then sent to the local municipality. The municiplality can use the information for local emergency management and response.

http://www.k-net.bosai.go.jp/

Modify the loss

On the same day, China's Chengdu Military Area Command dispatched 50,000 troops and armed police to help with disaster relief work in Wenchuan County.

An earthquake emergency relief team of 184 people (consisting of 12 people from the State Seismological Bureau, 150 from the Beijing Military Area Command, and 22 from the

Armed Police General Hospital) left Beijing from Nanyuan Airport late May 12 in two military transport planes to travel to Wenchuan County

California - Earthquake insurance is a form of property insurance that pays the policyholder in the event of an earthquake that causes damage to the property. Most ordinary homeowners insurance policies do not cover earthquake loss.

Earthquake insurance has become a political issue in California, whose residents purchase more earthquake insurance than residents of any other state in the U.S

Do nothing

NEvado del ruiz

The Armero Tragedy was the aftermath of the November 13, 1985 Nevado del Ruiz Volcano eruption in Tolima, Colombia. he eruption of lava melted the mountain's large ice cap and produced floods, mudslides and a series of lahars that ultimately covered the town of Armero and killed most of its population, over 20,000 people out of 29,000 inhabitants.

Geologists and other experts had warned authorities and media outlets about the danger over the weeks and days leading up to the eruption. When interviewed by reporters, a number of different officials told the inhabitants that the city was safe and downplayed the possible effects, possibly due to the cynicism created by previous false evacuation orders. The night before the explosion, the mayor of Armero himself assured citizens that there was nothing to fear.

A lack of preparation for the disaster contributed to the high death toll. Armero had been built on old mudflows; authorities had ignored a hazard-zone map that showed the potential damage to the town if lahar were to avalanche down the mountain. Habitants also stayed inside their dwellings and avoided the falling ash, not thinking that the mudflows would bury them, as officials from the area told them to.

www.mundoandino.com/Colombia/Armero-tragedy

Modify event

MT etna

^ Barberi, F., Carapezza, M.L., Valenza, M., Villari, L. (1993) The control of lava flow during the 1991–1992 eruption of Mt. Etna. Journal of Volcanology and Geothermal Research, vol. 56, p. 1-34

1992 eruption saw the town of Zafferana threatened by a lava flow, but successful diversion efforts saved the town with the loss of only one building a few hundred metres outside it.

Sicilyguide.com

During the 1992 attempt, the United States Marines worked with Italian volcanologists to develop “Operation Volcano Buster”, in which they used explosives to blast a hole in a lava tunnel on Etna’s flank and then dropped large blocks of concrete into the hole to try and stem the flow of the lava. Like the 1669 attempt, however, this plan was ultimately unsuccessful.

Modify the vulnerability

Ruapehu is the most intensively monitored volcano in New Zealand, reflecting its recent past of damaging eruptions. The principal surveillance tool is volcano seismicity. Ruapehu monitored by a single network of 6 seismometers. The system is designed to be triggered by either elevated levels of volcanic tremor or by discrete volcanic earthquakes.

Modify loss burden

The United Nations General Assembly designated the 1990s as the International Decade for Natural Disaster Reduction (IDNDR). its basic objective was to decrease the loss of life, property destruction and social and economic disruption caused by natural disasters,

The building of disaster resilient communities is a main objective. The ISDR promotes the following four objectives as tools towards reaching disaster reduction for all:

Increase public awareness to understand risk, vulnerability and disaster reduction globally

Obtain commitment from public authorities to implement disaster reduction policies and actions

Stimulate interdisciplinary and inter-sectoral partnerships, including the expansion of risk reduction networks

Improve scientific knowledge about disaster reduction