Science of Tsunami Hazards (Aug 2019)
EARTHQUAKE OF 21 FEBRUARY 2011 IN NEW ZEALAND Generation of Glacial Tsunami
Abstract
An earthquake with Richter magnitude 6.3 struck in the vicinity of Christchurch in New Zealand. It was the second largest seismic event to strike the area within a short time interval. Although of relatively small magnitude, the quake was extremely destructive as it struck much closer to the city than the previous earthquake of 4 September 2010. More than 180 people lost their lives. The earthquake occurred onshore, so there was no tsunami generated. Loss of power at the tide gauge of Lyttelton Port of Christchurch failed to record any wave activity. The GeoNet site at Sumner Head, which is located on the open coast, registered some longer period waves, but these were the result of weather related generation and not of seismic origin. According to eyewitnesses, the earthquake's motions were mild in Aoraki Mt. Cook National Park on the western side of New Zealand’s South Island, but the shaking triggered an icefall off the end of the Tasman Glacier’s lake and generated significant tsunami waves with an initial wall of water that was 50 or 60 meters high, but up to 3.5 meters high along its shores. The present study assesses the tectonic stresses and seismicity of the Marlborough fault system along the northern part of South Island, and briefly evaluates the potential of future tsunami generation from earthquakes that may be generated near New Zealand’s Hikurangi Trough, that may also impact the coasts of South Island as well as the coastlines near the City of Wellington on North Island.
