Increased Quake Activity, New Zealand

Earthquake activity in New Zealand has continued at an increased level during the first 4 days of October 2007.

Ten quakes with magnitudes between 2.8 and 5.7 have been reported in both main islands, with some reports indicating minor damage due to items that have fallen off shelves.

Earthquakes have been reported near Tauranga, Katikati, Matata, Porangahau, and Turangi in the North Island, and near Takaka, Hanmer Springs and Mount Cook in the South Island. The list includes two 2nd magnitude quakes near Turangi and Katikati, and four 3rd magnitude events near Matata (three) and Takaka.

The 4th magnitude quakes struck near Mt Cook and Turangi on October 1st.

Both of the 5th magnitude quakes struck yesterday, October 4th. A magnitude 5.6 quake struck 40 km north of Hanmer Springs at a depth of 70 km at 8:15 a.m. This quake was felt from Hamilton to Queenstown, and has attracted 2079 reports from members of the public who felt it. Thirty six of the respondents to the GeoNet website reported MM5 shaking. The Modified Mercalli system is used to compare the effects of an earthquake on property and people, as opposed to the Richter Magnitude which describes the amount of energy released at the earthquake’s epicentre.

The Modified Mercalli system adapted for New Zealand conditions, reports MM5 shaking as: “Generally felt outside and by almost everyone indoors. Most sleepers are awakened and a few people alarmed. Small objects are shifted or overturned, and pictures knock against the wall. Some glassware and crockery may break, and loosely secured doors may swing open and shut.”

Last night’s earthquake near Tauranga, which struck at 7:17 p.m., is the largest so far this month. The 280 km-deep magnitude 5.7 quake was located 20 km west of Te Puke, 20 km south of Tauranga. The quake’s depth meant that that it was felt outside the locality, and its damaging effects were limited. The 13 reports filed with GeoNet so far indicate the quake was felt in the South Island at Nelson and Christchurch, where it would have caused doors, windows and crockery to rattle, but no damage has been reported.

A burst of activity, to the south of New Zealand late on October 3rd and early on October 4th showed on southern seismographs, and data has begun appearing in earthquake databases. Traces indicate three moderately-sized quakes and five much smaller events. Traces this morning show a medium-sized magnitude 4.6 event at 10 p.m. last night with only 1 small event since.

[Compiled from data provided by the Geonet project and its sponsors EQC, GNS Science and FRST.]

3 Responses to “Increased Quake Activity, New Zealand”

  1. W Pryce says:

    The GeoNet site makes no mention of a 5.6 quake close to Hamner Springs on 4th October. Are you going to correct your report?

  2. Ken says:

    Yes there was, and GeoNet reported it.
    … in 2007 …
    4 years before you posted your comment.

    Don’t worry, an easy mistake to make. 🙂

  3. W Pryce says:

    Sorry, in my concern for family & friends in Tauranga, didn’t notice you were talking about 2007. That the quake this week was 5.7, the same as that of 4 years ago, almost on the same day brought on a bit of a blind panic, esp as another website initially showed confusion by quoting the 2007 details, which have now been replaced with those of the 2011 shake.

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