Table 6 The scenario timeline of Exercise Ruaumoko (MCDEM 2008 )
November 2007 | • Initial phase of the exercise: initial earthquakes characterised as ‘deep long period earthquakes’ and suspected by seismologists participating in the exercise to be of volcanic origin. Due to the rarity of such earthquakes in the Auckland region, the GNS Science/GeoNet exercise participants raised the Scientific Alert Level for the Auckland Volcanic Field to 1 (“Initial signs of volcanic unrest”)*. |
• Fourty eight hours later this seismic activity appeared to stop, with no observable shallowing of earthquake depths. The exercise scientists determined after a week of quiescence that “if there had been an intrusion of magma, it had likely stopped or ‘failed’ at a depth of 40–50 km” (MCDEM, p. 11). | |
• Scientific Alert level reduced to 0 (“Usual dormant or quiescent state”) on 16th November | |
March 2008 | • Second phase of the exercise: seismicity resumed and became sustained causing concern for the ‘exercising’ authorities and Auckland communities, as the seismic source progressively shallowed, indicating that a volcanic eruption may occur. However, the geographic distribution of earthquake epicentres indicated a few possible locations for such an eruption in the monogenetic field. |
3 rd March | • Scientific Alert Level raised to Level 1 (“Initial signs of volcanic unrest”) |
8 th March | • Scientific Alert Level raised to Level 2 (“Confirmation of volcano unrest”) |
9 th -12 th March | • Earthquakes started to be ‘felt’ across the Auckland region as the seismic source reached 20–25 km depth, and by 20 km more than 50 were being recorded a day. |
12 th March | • At 10–15 km depth the events exceeded 100 per day, and by 12th March the earthquakes started to cluster in one region (Mt Roskill-Hillsborough to Mangere), such that ACDEM started to draw up evacuation maps. |
12 th March | • Scientific Alert Level raised to Level 3 (“Real possibility of Hazardous eruptions”) |
13 th March | • Clustering of earthquakes refined further (Mangere Inlet) with 300 events ‘recorded’ in a 24 hour period with depths of 5 km and many being of Mercalli 4.5 and ‘felt’ by residents. |
14 th March | • By the morning of Friday 14th March, earthquake merged into tremor, increasing in strength throughout the morning with ground cracking and slumping observed around the Kiwi Esplanade and Mangere Bridge, and by 1.50 pm a small phreatomagmatic eruption had begun. |
14 th March | • Scientific Alert Level raised to Level 4 (“Hazardous local eruption in progress”) |
• End Of Exercise |