Earthquake Of February Research Articles

The Mw 6.2 Christchurch earthquake of February 2011: preliminary report

A moment magnitude (Mw) 6.2 earthquake struck beneath the outer suburbs of Christchurch, New Zealand's second largest city, on 22 February 2011 local time. The Christchurch earthquake was the deadliest in New Zealand since the 1931 Mw 7.8 Hawkes Bay earthquake and the most expensive in New Zealand's recorded history. The effects of the earthquake on the region's population and infrastructure were severe including 181 fatalities, widespread building damage, liquefaction and landslides. The Christchurch earthquake was an aftershock of the Mw 7.1 Darfield Earthquake of September 2010, occurring towards the eastern edge of the aftershock zone. This was a low recurrence earthquake for New Zealand and occurred on a fault unrecognised prior to the Darfield event. Geodetic and seismological source models show that oblique-reverse slip occurred along a northeast–southwest-striking fault dipping southeast at c. 69°, with maximum slip at 3–4 km depth. Ground motions during the earthquake were unusually large at near-source distances for an earthquake of its size, registering up to 2.2 g (vertical) and 1.7 g (horizontal) near the epicentre and up to 0.8 g (vertical) and 0.7 g (horizontal) in the city centre. Acceleration response spectra exceeded 2500 yr building design codes and estimates based on standard New Zealand models. The earthquake was associated with high apparent stress indicative of a strong fault. Furthermore, rupture in an updip direction towards Christchurch likely led to strong directivity effects in the city. Site effects including long period amplification and near-surface effects also contributed to the severity of ground motions.

Toward understanding tectonic control on the Mw 8.8 2010 Maule Chile earthquake

The Maule earthquake of 27th February 2010 (Mw=8.8) affected ~500km of the Nazca-South America plate boundary in south-central Chile producing spectacular crustal deformation. Here, we present a detailed estimate of static coseismic surface offsets as measured by survey and continuous GPS, both in near- and far-field regions. Earthquake slip along the megathrust has been inferred from a joint inversion of our new data together with published GPS, InSAR, and land-level changes data using Green's functions generated by a spherical finite-element model with realistic subduction zone geometry. The combination of the data sets provided a good resolution, indicating that most of the slip was well resolved. Coseismic slip was concentrated north of the epicenter with up to 16m of slip, whereas to the south it reached over 10m within two minor patches. A comparison of coseismic slip with the slip deficit accumulated since the last great earthquake in 1835 suggests that the 2010 event closed a mature seismic gap. Slip deficit distribution shows an apparent local overshoot that highlight cycle-to-cycle variability, which has to be taken into account when anticipating future events from interseismic observations. Rupture propagation was obviously not affected by bathymetric features of the incoming plate. Instead, splay faults in the upper plate seem to have limited rupture propagation in the updip and along-strike directions. Additionally, we found that along-strike gradients in slip are spatially correlated with geometrical inflections of the megathrust. Our study suggests that persistent tectonic features may control strain accumulation and release along subduction megathrusts.

The Impacts of the Canterbury Earthquakes on the Commercial Office Market in Christchurch, New Zealand

The 22 February 2011 Canterbury earthquake had a devastating impact on Christchurch property with significant damage caused to land and buildings. The broad aims of the research were to examine the nature and extent of the CBD office relocation, determine occupier’s perceptions of the future: their location and space needs post the February earthquake and the likelihood of relocating back to the CBD after the rebuild. An online survey was developed with the web link and a covering letter emailed to 643 companies. A follow-up survey was sent out in January 2012 following the December 2011 earthquake event to determine if respondents’ location choices had changed. From the initial survey, 55% of respondents were relocated CBD occupiers and 45% were existing suburban office occupiers. Of the businesses that relocated out of the CBD the biggest group (38%) want to return to the CBD into low-rise buildings of 3 floors or less (80%) that meet earthquake codes with good amenities and public transport. The speed of rebuild is important to respondents. The follow up survey indicated that demand for the CBD has fallen since the initial survey. In terms of building grade preferences, the response from occupiers is that although higher quality Premium or A-Grade buildings are preferred, when taking into account likely rental levels, occupiers prefer lower quality new or existing buildings. The concern with new builds is that rentals are likely to be too high for tenants to afford which was illustrated by the gap analysis of respondent expectations of rents and the indicative market rentals that will need to be achieved to make the rebuild feasible.

Christchurch City Council lifelines

On 22 February 2011 an earthquake measuring 6.3 on the Richter Scale occurred in Christchurch City resulting in widespread damage to buildings and infrastructure.
 Christchurch City Council (CCC) has an extensive potable water supply network including bulk storage and service reservoirs which provide water to approximately 320,000 residents. Inspections undertaken, following the 22 February earthquake, on 43 concrete reservoirs located on the Port Hills and Cashmere Hills areas noted varying extents of damage from nil through to major. Damaged roof to wall connections were observed in many reservoirs with damage to walls, base-slabs and internal columns limited to a few reservoirs only. Of the 43 reservoirs, complete functional failure occurred in only one, with reduced function and operation at other sites resulting from excessive leakage, necessity for emergency repairs, or associated pipe work damage. Those reservoirs currently out of operation for reinstatement, including Christchurch’s largest, account for approximately 40% of the network’s storage capacity.
 Overall, given the magnitude of earthquake accelerations that occurred on 22 February 2011, the reservoirs are considered to have performed remarkably well. Those in the Port Hills area nearest the earthquake epicentre, have expectedly, incurred the most damage.
 Reinstatement works, varying from minor crack injection and patch repair through to reconstruction and retrofit, have been developed appropriate to the extent of damage. CCC has prioritised reservoir repair to maximise available water supply for the 2011-2012 summer demand and this has required, in some instances, staging and deferring of reinstatement works.
 A summary of structural and functional performance, results of physical investigations and detailed seismic assessments, and common damage areas observed are presented in this paper along with the reinstatement options developed.

Performance of masonry buildings and churches in the 22 February 2011 Christchurch earthquake

As part of the ‘Project Masonry’ Recovery Project funded by the New Zealand Natural Hazards Research Platform, commencing in March 2011, an international team of researchers was deployed to document and interpret the observed earthquake damage to masonry buildings and to churches as a result of the 22nd February 2011 Christchurch earthquake. The study focused on investigating commonly encountered failure patterns and collapse mechanisms. A brief summary of activities undertaken is presented, detailing the observations that were made on the performance of and the deficiencies that contributed to the damage to approximately 650 inspected unreinforced clay brick masonry (URM) buildings, to 90 unreinforced stone masonry buildings, to 342 reinforced concrete masonry (RCM) buildings, to 112 churches in the Canterbury region, and to just under 1100 residential dwellings having external masonry veneer cladding. In addition, details are provided of retrofit techniques that were implemented within relevant Christchurch URM buildings prior to the 22nd February earthquake and brief suggestions are provided regarding appropriate seismic retrofit and remediation techniques for stone masonry buildings.

A Case of Recurrent Earthquake Stress Cardiomyopathy with a Differing Wall Motion Abnormality

We present the case of a Caucasian woman who survived two major earthquakes, presenting on each occasion with stress cardiomyopathy, but with a different pattern of regional wall motion abnormality on the second occasion. The first Christchurch earthquake struck on September 4, 2010. At 7.1 on the Richter scale, it was larger than the major Haiti quake, but miraculously there were no direct fatalities. In the week following, eight women meeting modified Mayo criteria for stress cardiomyopathy presented to Christchurch Hospital. The second Christchurch earthquake was on February 22, 2011. It measured 6.4 on the Richter scale and caused 180 direct fatalities. In the week following this earthquake, 24 women were admitted with stress cardiomyopathy. One patient presented after both earthquakes. This 76-year-old woman first presented on September 4 with 10 hours of chest pain. Electrocardiogram showed inferolateral deep T-wave inversion and QT prolongation. TnI peaked at 0.81 μg/L. Coronary angiography demonstrated diffuse atheroma with a moderate mid LAD lesion that was stented at the time. Echocardiography showed a classic takotsubo pattern. Her follow-up echocardiogram on September 28 was normal and she was completely well at that point. However, during the second earthquake of February 22, she again developed chest pain and shortness of breath. TnI peaked at 1.3 μg/L. Echocardiogram showed a midwall variant takotsubo with apical sparing. She was discharged from hospital on the 25th, planning to leave Christchurch for a new home in another city, but returned for follow-up echocardiogram on July 27. This was normal.

The 2010 and 2011 Canterbury earthquakes and organisational learning at the University of Canterbury: Does practice make perfect?

AbstractIn September 2010 and again in February 2011, the city of Christchurch was rocked by earthquakes of magnitude 7.1 and 6.3 respectively. The second earthquake was shallow and caused extensive damage and loss of life, destroying most of the Central Business District. This paper focuses on recovery management at the University of Canterbury, exploring the extent to which the senior management team learned lessons from the September event which informed the way that the recovery was managed after the February earthquake. It examines the counter-intuitive possibility that successfully dealing with a prior, lesser event, may not necessarily better equip managers to deal with a subsequent, more extreme event.

Kinematic Source Model of the 22 February 2011 Mw 6.2 Christchurch Earthquake Using Strong Motion Data

The Canterbury earthquake sequence began in September 2010 with the Mw 7.1 (source: GeoNet catalog, http://geonet.org.nz/canterbury-quakes/) Darfield earthquake that ruptured the previously unknown 40-km-long Greendale fault 30 km west of Christchurch (Gledhill et al. 2011). Extreme ground accelerations as high as 1.8 g near the epicenter were recorded. The event caused intense liquefaction in the eastern suburbs of Christchurch as well as closer to downtown, near the course of the Avon River. The Darfield earthquake was followed by a major aftershock on 22 February local time (21 February UTC) of magnitude Mw 6.2 (source: GeoNet), but Me 6.7 (source: USGS, http://earthquake.usgs.gov/earthquakes/eqinthenews/2011/usb0001igm/neic\_b0001igm\_e.php). This earthquake was centred only a few kilometers south of the Christchurch city center. Extremely high accelerations (as high as 2.2 g) were also recorded near the epicenter (Kaiser, Benites et al. 2011). In addition to the extreme liquefaction seen after the Darfield earthquake, this event also caused landslides, large rockfalls, widespread damage to earthquake-risk buildings in Christchurch, and, most tragically, about 180 casualties. Another large aftershock of Mw 6.0 (source: GeoNet), but with Me 6.7 (source: USGS), subsequently occurred on 13 June local time (12 June UTC) just a few kilometers south of the February event, causing further damage, landslides, rockfalls, and liquefaction. Following the Darfield earthquake, the GeoNet network (New Zealand National Hazard Monitoring Network) and its regional component the CanNet network (Berrill et al. 2011) was supplemented by the deployment of 13 additional strong motion instruments regionally (and another nine following the February earthquake). We used this dense network of strong motion instruments to constrain the source kinematics of the February event. We present the inversion scheme and discuss its limitations. These results are preliminary, since more thorough data processing is needed; however, they already provide a key model that will help in understanding the sequence …

The 2010 and 2011 Canterbury earthquakes and organisational learning at the University of Canterbury: Does practice make perfect?

AbstractIn September 2010 and again in February 2011, the city of Christchurch was rocked by earthquakes of magnitude 7.1 and 6.3 respectively. The second earthquake was shallow and caused extensive damage and loss of life, destroying most of the Central Business District. This paper focuses on recovery management at the University of Canterbury, exploring the extent to which the senior management team learned lessons from the September event which informed the way that the recovery was managed after the February earthquake. It examines the counter-intuitive possibility that successfully dealing with a prior, lesser event, may not necessarily better equip managers to deal with a subsequent, more extreme event.

Ground Motions versus Geotechnical and Structural Damage in the February 2011 Christchurch Earthquake

The Mw = 6.3 earthquake of February 22 was the strongest seismic event in a series of damaging aftershocks in and around Christchurch after the Darfield earthquake on 4 September 2010. The source of the Darfield earthquake was in a sparsely populated area and thus it caused no loss of life. Serious damage was mainly due to extensive liquefaction. By contrast, the Christchurch earthquake was generated on a fault in close proximity to the city, resulting in a death toll of 181 people. The Canterbury Plains are covered with river gravels that hide any evidence of past fault activity in this region. The newly revealed Greendale fault was therefore completely unknown. Only a portion of it was revealed on the ground surface during the Darfield earthquake. The second fault (the one that ruptured in February 2011) appears to be a continuation of the first, although no fault structure directly connecting the faults has been recognized. There is a debate among seismologists at this point whether this is a different fault from Greendale one or not (NHRP 2011a; NHRP 2011b; Geonet 2011). Due to its magnitude, shallow depth and close proximity to the city, the February earthquake proved particularly destructive for the central business district (CBD) of Christchurch, where buildings suffered extensive damage. Thanks to a dense network of strong ground motion stations, a large number of records have been obtained, which provide valuable information on the event and offer the possibility of relating the extent of damage to actual measurements of ground shaking. Apart from the southern part of the city on the hills and the Lyttelton port area, Christchurch is built on deep estuarine soil, which has been shaped in the last thousands of years by the ever-changing riverbed. Fine sands—the dominant soil type—and the …

Fault Location and Slip Distribution of the 22 February 2011 Mw 6.2 Christchurch, New Zealand, Earthquake from Geodetic Data

The 22 February (local time) MW ∼6.2 Christchurch earthquake occurred within the aftershock region of the 4 September 2010 MW 7.1 Darfield (Canterbury) earthquake (Gledhill et al. 2011). Both the Darfield and Christchurch earthquakes occurred on previously unknown faults in a region of historically low seismicity, but within the zone of plate boundary deformation between the Pacific and Australian plates. The Darfield earthquake caused surface rupture up to 5 m (Quigley et al. 2010, forthcoming), but none has been observed associated with the Christchurch earthquake. Geodetic data indicate that strain has been slowly accumulating within the region (Wallace et al. 2007; Beavan et al. 2002), and the presence of active subsurface faults was known or suspected ( e.g. , Pettinga et al. 2001). Earthquakes of magnitude up to 7.2 in this region had been allowed for in the national seismic hazard model (Stirling et al. 2002), but the observed high apparent stresses (Fry and Gerstenberger 2011, page 833 of this issue) and high ground accelerations (Fry et al. 2011, page 846 of this issue) had not been anticipated, particularly those experienced in the Christchurch event. These and other factors (Fry and Gerstenberger 2011, page 833 of this issue; Fry et al. 2011, page 846 of this issue; Holden 2011, page 783 of this issue), plus the close proximity of the February earthquake to Christchurch city center, were responsible for the major damage caused by the earthquake ( e.g. , Kaiser et al. 2011). A large amount of geodetic ground-displacement data is available to constrain the source of the earthquake, in part because we reoccupied nearly 200 GPS sites that had been observed following the Darfield earthquake, and in part because a number of space agencies collected synthetic aperture radar (SAR) data over …

Soil Liquefaction Effects in the Central Business District during the February 2011 Christchurch Earthquake

During the period between September 2010 and June 2011, the city of Christchurch was strongly shaken by a series of earthquakes that included the 4 September 2010 ( Mw = 7.1), 26 December 2010 ( Mw = 4.8), 22 February 2011 ( Mw = 6.2), and 13 June 2011 ( Mw = 5.3 and Mw = 6.0) earthquakes. The moment magnitude ( Mw ) values adopted in this paper are taken from GNS Science, New Zealand (http://www.geonet.org.nz); they are 0.1 units higher than the corresponding Mw values reported by the U.S. Geological Survey (http://earthquake.usgs.gov/earthquakes/eqinthenews/2011/usb0001igm/). These earthquakes produced strong ground motions within the central business district (CBD) of Christchurch, which is the central heart of the city just east of Hagley Park and encompasses approximately 200 ha. Some of the recorded ground motions had 5% damped spectral accelerations that surpassed the 475-year return-period design motions by a factor of two. Ground shaking caused substantial damage to a large number of buildings and significant ground failure in areas with liquefiable soils. The 22 February earthquake was the most devastating. It caused 181 fatalities and widespread liquefaction and lateral spreading in the suburbs to the east of the CBD and in areas within the CBD, particularly along the stretch of the Avon River that runs through the city. There were pockets of heavy damage in the CBD, including the collapse of two multistory reinforced concrete buildings, as well as the collapse and partial collapse of many unreinforced masonry structures including the historic Christchurch Cathedral in the center of the CBD. Soil liquefaction in a substantial part of the CBD adversely affected the performance of many multistory buildings, resulting in global and differential settlements, lateral movement of foundations, tilt of buildings, and bearing failures. The Mw = 6.2, 22 February 2011 earthquake …

Fine-scale Relocation of Aftershocks of the 22 February Mw 6.2 Christchurch Earthquake using Double-difference Tomography

On 22 February 2011 New Zealand time (21 February UTC), the MW 6.2 Christchurch earthquake occurred just 7 km southeast of the center of Christchurch city, New Zealand (Fry et al. 2011, Holden 2011, page 783 of this issue). There were 181 confirmed fatalities, and the damage to Christchurch city is estimated to be NZ$15 billion–$NZ20 billion (US$12 billion–US$16 billion). The event was well-recorded by the broadband and strong-motion national-scale GeoNet network (Petersen et al. 2011) as well as by the Canterbury regional strong-motion network (Avery et al. 2004). Since the 22 February earthquake, more than 2,700 further aftershocks have been recorded up to 1 May 2011, including 21 events with local magnitude ( ML ) greater than 5. Here we describe the initial relocation analysis for these aftershocks. The Mw 6.2 Christchurch earthquake is part of the larger aftershock sequence of the Mw 7.1 Darfield earthquake, which occurred at 16:35 3 September UTC, 2010. Seismological, GPS, and InSAR data all suggest that the earthquake rupture process for the Mw 7.1 Darfield earthquake involved failure of multiple fault segments (Beavan et al. 2010; Gledhill et al. 2011). A surface rupture for that earthquake, now termed the Greendale fault, extending ∼29.5 km and located ∼4 km south of the epicenter, is consistent with strike-slip faulting with an average horizontal surface displacement of ∼2.5 m (Quigley et al. 2010). The vast majority of the 7,400+ aftershocks following the Darfield earthquake are shallow, at less than 15 km depth. Figure 1 shows that, although many of the aftershocks occurred near the surface trace of the Greendale fault, intense clusters of aftershock activity have also occurred at the western and eastern ends of the Darfield fault trace, as well as north-northwest from the Darfield epicenter. The distribution of …

Is it possible to detect earlier ionospheric precursors before large earthquakes using principal component analysis (PCA)?

The goal of this study was to determine whether principal component analysis (PCA) can be used to process GPS ionospheric total electron content (TEC) data on a monthly basis to identify early earthquake-associated TEC anomalies. PCA is applied to GPS (mean value of a month) ionospheric TEC records collected from the Japan GEONET system to detect TEC anomalies associated with 10 earthquakes in Japan (M ≥ 6.0) from 2006 to 2007. According to the results, PCA was able to discriminate clear TEC anomalies in the months when all 10 earthquakes occurred. After reviewing the months when no M ≥ 6.0 earthquake occurred but the geomagnetic storm activity was present, it is possible that the maximal principal eigenvalues PCA returned for these 10 earthquakes indicate earthquake-associated TEC anomalies. Previously, PCA has been used to discriminate earthquake-associated TEC anomalies recognized by other researchers who found that a statistical association between large earthquakes and TEC anomalies could be established in the 5 days before earthquake nucleation and in 24 h before earthquake; however, since PCA uses the characteristics of principal eigenvalues to determine earthquake-related TEC anomalies, it is possible to show that such anomalies existed earlier than this 5-day statistical window. In this paper, this is shown through the application of PCA to one-dimensional TEC data relating to the earthquake of 17 February 2007 (M = 6.0). The analysis is applied to daily TEC and reveals a large principal eigenvalue (representative of an earthquake-associated anomaly) for 02 February, 15 days before the 17 February earthquake.

Strong shaking in recent New Zealand earthquakes

On 4 September 2010 a surface‐rupturing crustal earthquake (Mw 7.1) struck the Canterbury Plains region of New Zealand's South Island [Gledhill et al., 2011]. The Canterbury Plains is a region of relatively low seismicity in New Zealand, and the structure that ruptured was a previously unmapped fault (Figure 1a). Fortunately, even though parts of the region experienced liquefaction of unconsolidated sediments and sands—including neighborhoods of the city of Christchurch (population 377,000)—no fatalities occurred. Compared to the average New Zealand aftershock decay model, the aftershock sequence for the 2010 earthquake was relatively underproductive for the first 5 months. But on 22 February 2011 anMw 6.2 aftershock (teleseismic and regional estimates range from (Mw 6.1 to (Mw 6.3 with regional inversions favoring higher values) occurred within kilometers of the center of Christchurch (A. E. Kaiser et al., The (Mw 6.2 Christchurch earthquake of February 2011: Preliminary report, submitted to New Zealand Journal of Geology and Geophysics, 2011). The event increased the productivity of other aftershocks (Figure 1b). This particular aftershock was devastating, generating much more destruction than theMw 7.1 event, including more than 180 fatalities. Recorded peak ground acceleration (PGA) in the city was more than double the acceleration of gravity (g). Many of the poorly consolidated, low‐shear‐wave‐velocity soils liquefied during the shaking. Damage estimates reached approximately US$15 billion, making the aftershock New Zealand's costliest natural disaster.

Deep tremor in New Zealand triggered by the 2010 Mw8.8 Chile earthquake

Deep non‐volcanic tremor (NVT) is usually associated with episodic slow‐slip events. New Zealand is one notable exception where numerous slow slip events have been identified, yet NVT has remained undetected. Here we present the first known case of triggered NVT at New Zealand's Hikurangi subduction margin. Following the Mw8.8 Chilean earthquake of February 27, 2010, we identify coherent high‐frequency tremor signals that are in phase with, and modulated by, the passing Rayleigh waves. This is consistent with the surface wave triggering potential for strike‐normal incidence on a low‐angle thrust fault. After constraining the tremor depth on the plate interface, we locate the tremor source within 20 km of the source area of episodic slow slip. The tremor location is also near the edge of a region with high seismic attenuation that marks the boundary between dehydrated subducted slab and inferred hydrated, underplated sediment. We speculate that reduced interface friction and high fluid pressures provided by fluid‐rich underplated sediment facilitates the tremor generation.

Preliminary observations of the impacts the 22 February Christchurch earthquake had on organisations and the economy

On 22 February 2011, Canterbury and its largest city Christchurch experienced its second major earthquake within six months. The region is facing major economic and organisational challenges in the aftermath of these events. Approximately 25% of all buildings in the Christchurch CBD have been “red tagged” or deemed unsafe to enter. The New Zealand Treasury estimates that the combined cost of the February earthquake and the September earthquake is approximately NZ$15 billion [2]. This paper examines the national and regional economic climate prior to the event, discusses the immediate economic implications of this event, and the challenges and opportunities faced by organisations affected by this event. In order to facilitate recovery of the Christchurch area, organisations must adjust to a new norm; finding ways not only to continue functioning, but to grow in the months and years following these earthquakes. Some organisations relocated within days to areas that have been less affected by the earthquakes. Others are taking advantage of government subsidised aid packages to help retain their employees until they can make long-term decisions about the future of their organisation. This paper is framed as a “report from the field” in order to provide insight into the early recovery scenario as it applies to organisations affected by the February 2011 earthquake. It is intended both to inform and facilitate discussion about how organisations can and should pursue recovery in Canterbury, and how organisations can become more resilient in the face of the next crisis.

(A306) Community Resilience and the Christchurch Earthquake: Best Laid Plans or Practise Made Perfect?

On February 22, 2011 at 12:51 pm an earthquake measuring 6.3 on the Richter scale struck the city of Christchurch, population 376,700 in the South Island of New Zealand. This followed a 7.3 magnitude earthquake in September 2010, but the shallowness (5km) and proximity of the February earthquake to the central city, resulted in far more devastation, with Modified Mercalli scores reaching ten in some areas and upward ground acceleration exceeding 2.4G. The application of the Coordinated Incident Management System (CIMS) routinely used by New Zealand Civil Defence agencies was swift, innovative and efficient, facilitating rapid deployment of local and international emergency teams and response resources. The effectiveness of this response was partially attributed to lessons learnt from the September earthquake which, with hindsight, was a practise for the more serious February event. The community response was equally remarkable, with standard approaches to measuring preparedness and resilience suggesting that community resilience in Canterbury was high. A number of initiatives by the New Zealand Ministry of Civil Defence and Emergency Management may have fostered some of this resilience,particularly community- based resilience-building projects initiated by the Regional Emergency Management Office on 2009 and 2010, supported by the Ministry of Civil Defence and Emergency Management. In addition, website education resources and media promotion (“Get Ready Get Thru”) and a travelling exhibition called “The Pandemic Roadshow” had been particularly well received and remembered by Canterbury residents. However, two key events provided an impetus for the Canterbury community to burnish its resilience. First, the Swine flu (AH1N1) pandemic in 2009 resulted in a greater awareness of public health in emergencies along with a doubling of neighbourhood support groups. Secondly, the September 2010 earthquake resulted in the establishment of the student army of volunteers and improvement of public information management. This presentation will describe the markers of community resilience following the Christchurch earthquake and discuss how such resilience can be fostered in communities where emergency preparedness is not recognised as a priority.

South American SLR stations monitoring ground displacement caused by the M8.8 Chilean earthquake of 2010

The M8.8 Chilean earthquake of February 27, 2010 caused a large surface displacement near its epicenter. Satellite Laser Ranging (SLR) station 7405, cooperatively operated by Germany and Chile about 130 km from the epicenter was affected by the earthquake. Another SLR station, No. 7406, operated jointly by the National Astronomical Observatories of the Chinese Academy of Sciences and San Juan University of Argentina, was about 600 km from the epicenter. Combining the observations of these two SLR stations with global SLR station observations, we calculate the geocentric coordinates of the two stations based on ITRF2000. The results show that the coordinates of the two stations have changed by varying degrees. SLR-7405 moved substantially towards the southwest with displacements of about 3.11, 0.52 and 0.49 m in X, Y, Z directions; the corresponding displacements for SLR-7406 are about 0.02, 0.03 and 0.02 m. This solution, as an independent result derived from SLR observations, could provide an essential external check for other positioning techniques such as GPS.

Sedimentology and paleontology of a tsunami deposit accompanying the great Chilean earthquake of February 2010

Abstract At Pichilemu, in the northern third of the rupture area of the moment magnitude scale (Mw) 8.8 2010 Chile earthquake, deposits of the tsunami accompanying the earthquake consist of a lower layer of medium to fine sand (mean grain size of 200 μm) containing rock clasts, overlain by a thin, silty, very fine sand (mean grain size of 125 μm) layer. Based on a sedimentological model, most (90%) of the deposit is finer than 401–408 μm suggesting tsunami flow velocities were between 7 m/ s and 13.5 m/ s. Ostracods were common in the upper layer along with a small number of broken benthic foraminifera and a single planktonic foraminifera. Diatoms were abundant throughout. Species assemblages represent a mixture of diatoms from differing environments, life forms and substrate preferences. We attribute the mixed assemblages to turbulence within the water column during tsunami inundation, with erosion of beaches and salt marshes followed by redeposition of sand and mud inland. Breakage of fragile diatom valves in the lower layer may also support transport by turbulent flow. A higher abundance of diatom species with mud substrate preferences in the upper layer implies a decrease in flow velocity from lower to upper layers.