what does an Earthquake do to a city
Project instructions:
Week 1 – What does an earthquake do to a city?
In the past few years, there have been several earthquakes that have devastated populated areas. Here we will focus on two of these recent events – the 2010 Mw 7.0 Haiti earthquake (Jan 12, 2010) and the 2010 – 2012 earthquake sequence near Christchurch, NZ (including a Mw 7.1 main earthquake and several ~ Mw 6.0 aftershocks). Each of these events are rich in lessons for improving earthquake preparedness and response, and we will focus on two aspects: estimating immediate losses and response needs (Haiti) and linkages among events and consequences (Christchurch, NZ).
When a major (or potentially life-threatening) earthquake occurs globally, seismologists at the USGS National Earthquake Information Center (NEIC) produce an automated product termed Prompt Assessment of Global Earthquakes for Response (PAGER) that estimates both the extent of likely strong damage and also identifies the number of people exposed to various levels of ground shaking (based on the Modified Mercalli Intensity (MMI) scale. Pager reports are generated as soon after the event as possible (initial versions are generated within 20-30 minutes) and these are updated (with new version numbers) as more information is available. Pager is still a product under development and so its format has changed over the past several years. Two examples of the current version of Pager products are Provided in the following figures:
Haiti Pager 1a and Haiti Pager 1 show Pager outputs produced immediately after the Haiti event (Haiti Pager 1a was the normal version produced at that time and Haiti Pager 1 is termed a Beta version since it was using what at that time was an experimental format). At that time (approximately 20 minutes after the earthquake) basically seismologists at NEIC knew the location of the earthquake, and its magnitude. They also had information (in their database) of local geology, population distribution, caliber of buildings and infrastructure, and other site specific parameters. More recently the version including estimated deaths and damage for the Pager reports has been made operational and Haiti Pager 2 shows the updated report. (Note that this version was made 36 weeks after the earthquake – although labeled Version 1(in the new format) it corresponds to Version 9 in what was at that time the operational versions of Pager). Pager reports are aimed at the science and response communities to help in the immediate planning and execution of response to the event.
Activity 1. What is the actual damage?
Haiti
In addition to estimates of ground shaking (earthquake intensity) it is important to relate that to actual likely damage. One wants to be able to answer questions regarding numbers or percentage of buildings damaged or collapsed and the expected needs of the local population. One tool that has become available for this purpose is satellite imagery, that can be used to generate pictures of the damage zone even before emergency response teams arrive. We will use such before and after images for a small region of Port-au-Prince, Haiti to estimate extent of damage.
Haiti Before and Haiti After show a section of central city Port-au-Prince before and after the earthquake. Haiti Aerial After shows an oblique air-photo of part of the same scene to give you a sense of what the region looks like after the event.
Based on the Pager results, this section of Port-au-Prince experienced shaking at MMI VIII (eight), which can produce severe shaking and moderate-to-heavy damage in Resistant Structures and heavy damage in Vulnerable Structures.
Using the photos estimate the the following pieces of information for the region shown in the satellite photos:
Number of Buildings
Number of Buildings Destroyed
% Buildings Destroyed
Number of Damaged Buildings
% Damaged Buildings
# of Potentially Trapped People
Clearly making many of these estimates is difficult. You should discuss this with your fellow classmates in the Haiti Discussion Forum and make criteria and estimates that you are comfortable with. The figure Port au Prince Damage shows a regional perspective with results from a similar analysis done soon after the earthquake for key buildings. The region of your study is shown.
Deliverable: Please turn into the Haiti Drop Box your values for the table above, include a 1-2 paragraph description of the assumptions you made and criteria you used to arrive at these values. [After you have completed this activity, you should check out what the region looked like about 10 months after the earthquake. Port au Prince 10 Months After is a google image of the region from Nov 11, 2010.]
Christchurch
Although the damage to Christchurch NZ from its M 7.1 earthquake and major aftershocks (it is important to note that the major damage and deaths in the Christchurch sequence have come from a Mw 6+ aftershock and not the original Mw 7.1 mainshock) is less than that to Haiti (and the death toll was approximately only 1-2 % of the deaths in Haiti), the Christchurch sequence points out the vulnerability of modern cities in the developed world (with strict building codes) to moderate earthquakes.
As a result of the earthquakes and damage, the NZ government has convened a Royal Commission to study the causes and response to the earthquake sequence and its damage. The Interim Report of the Canterbury Earthquakes Royal Commission is provided in the eReserves. This report covers a wide range of issues and should provide a sense of the interaction of cause and impact for earthquake events.
You may also find the iTunes U, ?Putting the 2010 Canterbury Earthquake into Context?, iTunes U, University of Waikato, presentation of use. It is one I presented at Waikato University a few weeks after the initial Mw 7.1 earthquake. It provides a background of the setting for the earthquakes and provides explanations of what happened and what might happen in the future. It did not foresee the significant damage of the later events, but does provide a context under which the aftershocks became damaging and deadly.
Activity 2. What else happens to a city?
Please read over the Interim Report and identify one issue raised by the investigations that if of particular interest to you. Write an approximately 2-page (~ 1000 word) summary of the issue raised, why it is important in terms of earthquake damage mitigation and/or response, and what the key recommendations are for the future. You may wish to undertake some research on the topic. (Although Wikipedia can be a useful tool for searching for materials, please do not use it as a primary reference, rather search out original sources as much as possible.) For events such as this that continue to unfold in real-time, news media reports can often-times be useful resources – for New Zealand news, www.stuff.co.nz is a good source, and has a wealth of news reports regarding this earthquake sequence.
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