Learning from Earthquakes: First person reports

Aftershock Sequence

March 19, 2011 by

Aftershocks in Canterbury have persisted since the 4 September 2010 M 7.1 event with 200 aftershocks greater than 4.0 and 15 greater than 5.0.   The period prior to 22/2/2011 contained fourteen events of magnitude 5.0 to 5.6 and forty events of magnitude 4.5 to 5.0. Since 22/2/2011 there have been five aftershocks between 5.0 and 6.3 and eighteen between 4.5 and 5.0.

Christchurch area aftershock sequance - Sep 2010 - Mar 2011

Christchurch area aftershock sequence - Sep 2010 - Mar 2011

Christchurch is built on the fine alluvial soils of previously-braided rivers and mashes.  Many of the larger aftershocks liquefied new soil and re-liquefied previously-liquefied ground.  This activity has slowed the consolidation of large liquefied areas.

This aftershock sequence is active as compared to parametric stochastic aftershock models for both New Zealand and California (Reasenberg and Jones 1989, Reasenberg and Jones 1994, Eberhart-Phillips 1998, Tormann et al 2008). Further, center-city ground motions during the 22/2/2011 aftershock were 50% to 100% stronger than those of the 4/9/2010 primary shock, and exceeded the 10%/50yr uniform hazard spectrum by 60% to 80% at periods from 0.5 s to 2.0 s (Bradley 2011). While the strong motion responses prior to February 2011 could have contributed to progressive weakening of collapse-sensitive structures, the ground motion intensity of the 22/2/2011 aftershock is certainly the dominant factor contributing to these collapses. This event underscores the importance of modeling earthquakes as an event process.


Bradley, B., (2011) “Comparing the ground motion of the Feb 2011 quake to the September 2010 quake”  http://db.nzsee.org.nz:8080/en/web/chch_2011/home , retrieved 24 February 2011.

Eberhart-Phillips, D., (1998)  “Aftershock sequence parameters in New Zealand,”  Bulletin of the Seismological Society of America, v. 88; n. 4; p. 1095-1097.

Reasenberg, P.A. and Jones, L.M., (1989)  “Earthquake Hazard After a Mainshock in California”,  Science, v. 243, p. 1173-1176.

Reasenberg, P.A. and Jones, L.M., (1994)  “Earthquake Aftershocks: Update”,
Science, v. 265, p. 1251-1252.

Tormann, T., Savage, M.K., Smith, E.G.C., and Stirling, M.W., and Wiemer, S., (2008)  “Time-, Distance-, and Magnitude-Dependent Foreshock Probability Model for New Zealand,”  Bulletin of the Seismological Society of America, v. 98; n. 5; p. 2149-2160.

understanding the past

March 18, 2011 by

Friday was our last day in Christchurch. The government declared it a national holiday and held a memorial service in the CBD.

We took a few hours to look at evidence of the Greendale Fault Rupture from the Darfield September 2010 Mw7.1 Earthquake. While the trace was still visible in many places and kinks in roads and fences where still prominent its expression was slowly fading. The cleared fields that had once clearly shown the trace were now overgrown with vegetation and the fault scarp was slowing slumping to a diffuse hump.

This brought to my attention the importance of understanding the earth’s past when assessing hazards and risk today.

- Parts Christchurch are built on an old alluvial system comprised of meandering channels that controls the distribution of liquefiable sediments. Liquefaction hazard was recognized in ChCh, but the magnitude and spatial distribution of liquefiable sediments was not known in enough detail to lesson the hazard.

- Most of the slopes and cliff in the hilly east of ChCh have evidence of historic rockfall. The large boulders help create a beautiful landscape. These are areas where rockfall hazard has always been recognized, but the extent of the hazard when triggered by an earthquake was overlooked.

- The fault rupture in the Canterbury Plain is a stark reminder of the earthquake and it potential to cause damage, but within a few seasons it will subtly blend back into the landscape to be only represented by a line on a map.

Competing information, complementary information, coordinating information

March 17, 2011 by

The use of social media in disaster is often described as “drinking from a fire hose.” For those tuned in to social media , who monitor information flowing freely from citizen reporters on the disaster-affected streets, there is often so much information flowing that it is incredibly difficult to identify relevant and actionable data that can be turned into “intelligence.”

On the flip side is the perspective of the local public, looking for information that will enable them to make decisions about protective actions such as evacuation and sheltering. Under the traditional media strategy, information flows slowly, sometimes only two or three times a day. People perceive this as an information dearth just as they become all the more hungry for accurate and trustworthy information. At this very time, in the absence of information, local community members are turning to sources online. Similar to those emergency managers who are “drinking from a fire hose,” members of the public are faced with an overwhelming set of information sources such as websites, weblogs, major media, and social media networks (to name a few), some of which are authoritative and many of which are not. Without a central, authoritative site members of the public must make serious evaluations about which information will lead to their decision making and actions.

Throughout this short week of information gathering in the field, I’ve noticed that while there is the appearance of competing information sources, they have the potential to serve as complementary sources at varying points of disaster response. For instance, volunteer technical communities that mobilize resources early on aggregate and map information from the crowd. This is a complementary activity to those serving in official capacities that are responsible for critical infrastructure and emergency response. There are other examples that also show this complementary nature of efforts that may or may not duplicate data sources, but serve specific populations and needs at varying points of the response.

Key to the potential success of this kind of complementary effort is likely to be intentional actions to collaborate across organizations and to invite new partners to the table. Such collaborations have the possibility to strengthen communication processes, to increase trust, and to ensure that people are directed to verified information from which they can make informed decisions.

Toilet Inequality

March 17, 2011 by

It’s a stinky subject to write about, but there is toilet inequality in disaster response and recovery. Here in Christchurch, the sewerage system has been inoperable for varying periods of time depending upon the location you live. This has meant that many Cantaburians have been reliant on port-a-loos and other waste systems for the past three to four weeks.

There are differences in port-a-loos, I have learned. There is the deluxe version that can be found on the University Campus. These have flush systems, running water for hand washing and even a little mirror in the door. The next step down may be the regular port-a-loos that can be found on street corners throughout the eastern suburban neighborhoods. These are your common port-a-loos that you might find on a construction site. In addition, some people living in Christchurch have received chemical toilets – a box with a toilet seat on top of it that can be used by an individual household. Then there are others who seem to commune with nature in their own back yards. If they are capable, they dig a “longdrop box” and build a structure around the box (you can see pictures of these longdrop boxes online at www.ShowUsYourLongDrop.co.nz). Those who aren’t capable of strenuous digging, might dig a “shortdrop box” in their backyards. It’s the same idea as the longdrop, just not as deep into the ground.

Consider for a moment, issues of access and distribution of these various toilet facilities. One of our first conversations with a local Christchurch resident centered on this very issue. He told of a friend who has elderly parents who have lived for the past three weeks without a toilet. This elderly couple was unable to dig a drop box in their back yard; they are not mobile enough to get to the porta-loo down the street; and after multiple requests they have not yet received a chemical toilet for their own household. Our interviewee had a working sewer, was able bodied, and was contributing to the earthquake response through both professional and voluntary activities. At one point in our conversation he expressed some disappointment that he had no need to participate in the longdrop box activities around town. However, three weeks into the response, a chemical toilet was delivered to his front door.

In every disaster there are stories where people having great need go without resources for long periods of time. Why this is so, explained our Christchurch informant, might be that there is a lack of coordinated information to facilitate the transfer of resources to the right doorstep at the right time.

Raw, Real, and Open: UCSA Communications

March 17, 2011 by

The University of Canterbury Student Association has a clear strategy for online communications with their students at the Uni: honest, unfiltered, and raw. “Facebook is designed to be conversational,” explained their student services manager, Steve Jukes, “we want bad press as well as good press and we respond to every single comment that is posted on our wall.”

The man responding to every single comment is a twenty-something guy named Ryan. In his spare time he runs an online comedic site, similar to The Onion in the U.S. He brings levity and spirit to his work at the UCSA Facebook site as he interprets official University communications for students, bringing news to them using “real language” that isn’t sugar coated.

This approach, according to Steve, seems to be working. The daily traffic to the UCSA Facebook site catapulted in the days following the earthquake and Ryan and other staff began to catalog the concerns being posted by students. As the University management made decisions to cancel spring graduation ceremonies, the UCSA caught wind of student discontent and advocated their rights to the Vice Chancellor. While University schedulers focused on classroom space and teaching schedules, students expressed concerns about non-academic issues relating to information flow and financial aid. Once again, by observing social networks online, the UCSA identified student needs and was able to relay them to University officials.

This intentional community dialog stands out among other University strategies for communication. Rather than control the flow of information, the UCSA has chosen to engage, allowing for snarky comments as well as words of thanks. Meeting the psycho-social needs of connection and honesty is viewed by UCSA staff as being just as valuable as the uni-directional and controlled message of university officials; perhaps more so.

Social Media and Christchurch Emergency Communication

March 17, 2011 by

During the September 4, 2010 earthquake, the Christchurch City Council had no use of, or strategy to implement social media into their risk and crisis communications plan. Thoughtful observers who also endured that harrowing event found that local community members were turning to online social networks to organize volunteer efforts, post critical information, and communicate about the aftermath of the earthquake. The quick study from a few public information officers working for the CCC served as the impetus for the social media response during the devastating February 22, 2011 earthquake.

During this event, public information managers quickly rallied to develop a social media monitoring and publication strategy. They integrated a set of online platforms such as a WordPress blog that could be quickly updated as needed, twitter feeds, local news sources, annotated maps, and a Facebook fan page. These online technologies were used for both outgoing communication and incoming communication, facilitating a dialogue rather than just unidirectional information flow. They also observed milling activities, identifying critical needs that might be reported by those from the disaster affected areas so that resources could be directed to appropriate locations. Such a mixed strategy allowed the CCC to observe, communicate, distribute, and connect with members of the public through accessible web based technologies.

Crisis Camp New Zealand

March 17, 2011 by

Over the past two years we have witnessed a surge of online activism as technology volunteers, hackers and geeks donate their time, skills, and expertise to the disaster response cause. Armed with a “digital pick axe” these international volunteers work selflessly to monitor social media, crowdsource data, and develop useful applications for on the ground responders. They coordinate virtually around the clock and interface with official responders to identify data sources that can be mapped, translated, spread sheeted, and made into useful and actionable intelligence.

In the immediate aftermath of the earthquake, one such volunteer technical group quickly mobilized across New Zealand and integrated a worldwide effort to capture publicly available data and aggregate it for those directly affected by the disaster. The efforts of CrisisCampNZ, known locally as the website eq.org.nz, concentrated on crowdsourcing tweets, texts, email, web reports, and usahihidi applications on smart phones. They developed publicly available maps that were useful in the first hours after the ground shaking, alleviating the local responders who were addressing local critical issues.

rockfall and landslide photos

March 17, 2011 by

rockfall and landslide photos

“Switch” on to Business Resilience, Anne Wein, U.S. Geological Survey

March 17, 2011 by

Businesses in the CBD have been closed for a couple of weeks and will be for months and years. A staged and controlled re-entry process was set up to allow property and building owners to retrieve critical items (e.g. computers and business essentials) from safe (yellow and green placarded) buildings. On subsequent re-entries during the third week, owners were going into clean up. The owner of Switch Expresso shared that he and family members were returning to clean out the rotting food from the refrigerators. However, his business has proven to be a resilient organization and is booming. First, the owner had another establishment in New Brighton outside of the cordon area. Second, this café had a back-up generator that supported limited operations. Once electric power service was restored the business was able to overcome remaining issues by procuring roasted beans from another source (roaster is in the café in the CBD), receiving financial support from the government (paperwork for business interruption insurance was in process), and posting signage to the nearest porta loo (waste water system outage). The Switch Café business resilience strategies of distributed locations, back up power, and input substitution were made effective by government aid and city council provision of porta loos.

Nonstructural Observations

March 16, 2011 by


Mary Comerio

This earthquake has provided textbook examples of non-structural damage in concrete office and commercial buildings in the CBD.

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