This week (August 13-15, 2018) marks the 150th anniversary of one of the largest tsunamis in history. The tsunami was devastating in the source area along the Peru/Chile border and was recorded throughout the Pacific with significant effects including one death in New Zealand.
Magnitude: At least Mw 9.0
(UTC): 2130 hrs, August 13, 1868
(Source): 1730 hrs, August 13, 1868
(NZST): 0930 hrs, August 14, 1868
The 14th of August 1868 was a typical mid winter’s day throughout New Zealand. Coastal residents and workers went about their day completely unaware that one of the most powerful earthquakes the earth has ever produced had occurred in South America and that a deadly tsunami was at that moment racing across the Pacific Ocean towards them.
Occurring at approximately 5:30 PM local time in Arica (which was then part of Peru, but is now the northernmost city of Chile), the earthquake completely devastated the port city. The earthquake was followed by a series of tsunami waves producing runup heights of approximately 15-20 m. Three large naval vessels (two American ships, the Wateree and the Fredonia and one Peruvian ship, the America) were in port at the time. The tsunami completely destroyed Fredonia, killing all but two of its crewmen, and grounded the other two vessels hundreds of meters inland. To this day, the rusting steel boilers of the Wateree sit in the sand hundreds of meters from shore.
(above) The city of Arica, flattened and the Peruvian warship America beached after the waves (source: Wikipedia).
(above) The USS Wateree as it was after the tsunami and as it can be found today. (Source: Wikipedia and Jose Borrero personal collection)
It took more than 13 hours for the waves to reach New Zealand waters arriving in the early hours of August 15, 1868. The surges first affected the Chatham Islands where a village was washed away and one man was killed as he tried to secure a boat. An hour later the surges began affecting the east coasts of the North and South Islands with the strongest and most disruptive effects occurring in the ports and harbours.
(above) Computer simulation of the 1868 tsunami showing the maximum tsunami amplitudes across the Pacific. The white lines are 1-hour travel time contours for the tsunami wave front. (Data used with permission from the National Center for Tsunami Research and plotted by Jose Borrero, eCoast)
(above) Snapshots of the tsunami crossing the Pacific at 6, 10 and 14 hours after the earthquake. To see it animated, click here.
The historical record is filled with descriptive accounts of the tsunami affecting New Zealand. GNS’ New Zealand Tsunami Database is an excellent resource for reading in detail exactly what happened around the country as a result of the tsunami.
As noted above, the tsunami was most evident in the ports and harbours. Among these, the Port of Lyttelton in Christchurch was hit particularly hard with tsunami heights (peak to trough) of over 7 m causing extensive damage and strong currents that ripped boats from their mooring and causing numerous collisions.
(above) Snapshot of simulated tsunami currents from the 1868 tsunami along Cashin Quay in Lyttelton Harbour. See it animated here and here. Tsunami modelling done with the MOST tsunami model by Jose Borrero of eCoast.
(above) Simulated tide gauge record of the 1868 tsunami in Lyttelton Harbour. The dashed black line is the predicted tide curve for that day. The red line is the simulated tsunami + tide. The simulation matches well with historical accounts describing the initial drawdown of the water level some time around 3:30 AM, as well as with observations of water level fluctuations of ~25 feet (7.6 m) as indicated by the vertical black line.
So why should we care? This happened 150 years ago, what’s the big deal?
Well, the point is, it is going to happen again and New Zealand needs to be prepared!
Not all tsunamis cause the devastating ‘walls of water’ that we saw on television after the March 11, 2011 Japan earthquake. Those types of effects occur in the immediate source regions of powerful earthquakes, as was the case in Japan.
While New Zealand is indeed susceptible to those types of tsunami, we are also vulnerable to large tsunami generated from around the Pacific Ocean. These types of tsunami, known as ‘distant source’ or ‘far-field’ tsunami are much more likely to occur and affect New Zealand.
Recent tsunami events, such as the 2004 Boxing Day tsunami in the Indian Ocean and the 2010 Chile and 2011 Japan events in the Pacific, have each caused damage and/or disruption to port and maritime facilities at locations hundreds or thousands of kilometres away from the tsunami source region.
In the case of the 1868 tsunami, if it were to happen today, New Zealand could expect disruption and damage in several east coast ports. Lyttelton would be the most vulnerable with others such as Marsden Point, Gisborne, Napier, and Timaru all experiencing significant effects including strong currents, damage and possible shutdown of operations.
(above) Eddies (or whirlpools) such as this are a common feature caused by tsunami currents in ports or harbours.
Presently eCoast is working with the Northland Regional Council and Northland Civil Defence Emergency Management (CDEM) Group on a project sponsored by the Ministry of Civil Defence & Emergency Management to better understand the tsunami hazards in maritime facilities. The project builds on/extends existing tsunami modelling for the Northland Region and involves extensive computer simulations of tsunami effects in the ports and harbours as well as a detailed assessment of the types and condition of the infrastructure that is present at each facility.
The project aims to produce products designed to be used for on-the-ground emergency managers during an actual tsunami event. This will be done by producing decision-making ‘playbooks’ and harbor-based hazard maps that clearly define areas susceptible strong currents with the overall objective of reducing the uncertainty during the next tsunami so that disaster managers know what to do under a particular set of circumstances. The project is slated to continue through the year with results and products coming online in late 2018 or early 2019.
(above) An example of a prototype current speed hazard map produced for Marsden Point at the entrance to Whangarei Harbour in Northland. Modelling by Jose Borrero, eCoast
(above) Boats struggle at their moorings as surges and currents generated by the 2011 Japan tsunami force their way intoTutukaka Harbour, Whangarei , New Zealand, Saturday, March 12, 2011. Credit:NZPA / Malcolm Pullman
For more information see:
EARTHQUAKE AND TSUNAMI OF 13 AUGUST 1868 IN ARICA, PERU – Website of Dr. George Pararas – Carayannis
1868 Arica Earthquake – Wikipedia
Scientific Journal Articles
Borrero, J.C., Lynett, P.J. and Kalligeris, N. (2015) Tsunami Currents in Ports, Philosophical Transactions of the Royal Society A ,373: 20140372. http://dx.doi.org/10.1098/rsta.2014.0372.
Borrero, J.C., Goring, D.G. (2015) South American Tsunamis in Lyttelton Harbor, New Zealand, Pure and Applied Geophysics, 10.1007/s00024-014-1026-1.
Borrero, J.C., Goring, D.G., Greer, S.D. and Power, W.L. (2014) Tsunami Hazards in New Zealand Ports, Pure and Applied Geophysics, 10.1007/s00024-014-0987-4.
Lynett, P.J., Borrero, J.C., Son, S., Wilson, R.W. and Miller, K. (2014) Assessment of the tsunami-induced current hazard, Geophysical Research Letters, DOI: 10.1002/2013GL058680.