article: Mar 15 2005 - Deep Earthquake Extensively Felt

Monday morning's earthquake was felt over a wide area due to its size and depth.

The felt questionnaire responses from Monday morning's magnitude 6.4 earthquake have been compiled and are shown on the accompanying map. The epicentre is shown by the letter "E" in green relief. To date, 1871 reports have been received. The 150 km depth of the earthquake meant that only minor damage was caused by an event of this magnitude. It was too deep to cause a rupture in the earth's crust directly under the sea floor, hence there was no likelihood of a tsunami being generated.

However, due to its size and depth, it was felt over a very wide area, with strongest shaking detected by our instruments along a line between Paraparaumu and Porirua. This is a common phenomenon with deep events on the North Island subduction zone - the strongest shaking is felt to the south-east of the epicentre where it intersects a line from East Cape to Blenheim. This is because the energy that is released by the earthquake propagates more efficiently up the denser subducting Pacific plate, rather than the overlying Australian plate.

Previous large deep earthquakes detected in a similar location since 1965:

• Magnitude 6.1 on Tuesday, August 8 1989 at 7:59 pm
• Magnitude 5.9 on Tuesday, February 18 1992 at 11:27 pm
• Magnitude 5.9 on Thursday, April 27 2000 at 9:14 pm

For Monday morning's event, the Modified Mercalli (MM) shaking levels, the brief definition of their effects on people, and the localities that experienced them, are shown below. Where a number appears in square brackets [n], 'n' reports were received from that locality:

• MM 6 - "Felt by all. People and animals alarmed. Many run outside. Difficulty experienced in walking steadily":
  Manaia, Paekakariki, Plimmerton, Raumati Beach, Upper Hutt, Whitby [2].
  
  
• MM 5 - "Generally felt outside, and by almost everyone indoors. A few people alarmed":
  Aokautere [2], Aramoho [2], Ashhurst, Atawhai [2], Avalon [2], Avonside, Awapuni, Beckenham [5], Belfast, Belmont [2], Berhampore [4], Bishopdale, Blenheim [4], Boulcott, Brooklands, Brooklyn [6], Burwood [3], Camborne, Cannons Creek, Carterton [2], Cashmere, Christchurch [13], Churton Park [5], Collingwood, Crofton Downs, Dallington, Eastbourne, Elsdon, Eltham, Epuni, Fairfield, Featherston [7], Feilding, Fitzroy, Foxton [3], Foxton Beach [2], Frankleigh Park, Gisborne, Glenside, Gonville, Governors Bay, Harbour View, Harewood, Hataitai [8], Hawera [2], Heretaunga [2], Highbury [2], Hokowhitu [5], Houghton Bay, Inglewood, Island Bay [8], Johnsonville [11], Kaiteriteri, Kaitoke, Kapiti Island, Kaponga, Karori [9], Karori West [4], Kelburn [9], Khandallah [9], Kilbirnie [2], Kopuaranga, Korokoro [2], Kotinga, Levin [5], Linden, Linwood [3], Lower Hutt [14], Lower Moutere, Lyall Bay [3], Makara [2], Manaia [2], Maoribank, Mapua, Marahau, Martinborough, Marton, Masterton [9], Maungaraki [3], Maxwell, Melrose, Merivale, Merrilands, Miramar [8], Mitchelltown, Moera [2], Mornington, Motueka [2], Mount Cook [2], Mount Victoria [5], Murchison, Naenae [3], Nelson [5], Nelson East [2], Nelson South [2], New Brighton, New Plymouth [4], Newlands [12], Newtown [9], Ngaio [10], Normanby, Normandale [4], Norsewood, Northland [6], Ohakune, Okuti Valley, Omata, Opawa, Opunake [2], Otaihanga [2], Paekakariki [7], Palmerston North [12], Papakowhai, Papanui, Paparangi [2], Paraparaumu [14], Paraparaumu Beach [14], Paremata [4], Petone [4], Picton [4], Pinehaven, Pirinoa, Plimmerton [2], Porirua [3], Porirua East [5], Port Motueka, Port Underwood, Pukerau Bay, Pukerua Bay [4], Puponga, Raumati Beach [8], Raumati South, Redwood, Richmond [4], Rongotai [2], Roseneath, Roslyn, Sanson, Seatoun, Shirley [3], Silverstream [2], Somerfield [2], South New Brighton, Southshore, Spreydon, Springvale, Stoke [6], Stokes Valley [8], Strandon, Summerhill, Tahunanui [5], Taita, Tarurutangi, Tawa [22], Te Marua, Te Ore Ore, Titahi Bay [9], Totara Park, Trentham [3], Umutaoroa, Upper Hutt [16], Uruti, Vogeltown, Wadestown [4], Waikanae [7], Waikanae Beach [3], Wainuiomata [13], Waiouru Military Camp, Waitara, Waiwhetu, Wakefield, Wallaceville [2], Wanganui [3], Wanganui East [3], Waterloo, Welbourn, Wellington [55], West End [2], Westmorland, Westown, Whitby [14], Whitemans Valley, Wilton [3], Woodbourne, Woodville.
  
  
• MM 4 - "Generally noticed indoors but not outside. Vibration may be likened to the passing of heavy traffic, or to the jolt of a heavy object falling or striking the building":
  Addington, Akaroa, Alicetown [3], Aokautere, Aramoho [4], Aranui, Aria, Ashhurst [3], Atawhai [7], Auckland, Avalon [5], Avonhead, Avonside, Awapuni [2], Beckenham [2], Bell Block, Belmont [4], Berhampore, Birchville [4], Bishopdale [4], Blenheim [25], Boulcott [2], Brightwater, Broadmeadows [3], Brooklands, Brooklyn [12], Bryndwr, Burnside [2], Camborne [2], Cannons Creek, Carterton, Casebrook, Cashmere [2], Castlecliff [2], Catons Bay, Chartwell [2], Christchurch [37], Churton Park [8], Cloustonville, Cloverlea, Colyton, Crofton Downs [3], Dallington [4], Dannevirke [3], Days Bay, Diamond Harbour, Durie Hill, Eastbourne [3], Eltham, Endeavour Inlet, Enner Glynn, Epuni [3], Fairfield, Featherston [5], Feilding [3], Fendalton, Foxton [2], Foxton Beach [2], Frankleigh Park, Gisborne [2], Glen Avon, Gonville, Greenacres, Grenada Village [2], Greta Valley, Greymouth, Hanmer Springs, Harbour View, Hataitai [7], Havelock [2], Havelock North, Hawera [9], Heathcote Valley, Heretaunga [3], Hillmorton, Hokitika, Hokowhitu [7], Homedale, Hoon Hay [3], Huntsbury, Ilam, Inglewood [6], Island Bay [14], Johnsonville [15], Kahutara, Kaiapoi [8], Kaikoura [3], Kaitoke, Kaponga, Karamea [2], Karori [22], Karori West [2], Kelburn [11], Kelson [4], Kelvin Grove, Khandallah [17], Kilbirnie [6], Kingston, Korokoro [2], Kotinga, Lake Ferry, Levin [12], Lincoln, Linden [5], Linwood [3], Little River, Lower Hutt [19], Lowry Bay, Lyall Bay [9], Lyttelton [2], Mahoenui, Mahora, Mairehau [2], Makara Beach, Mana, Manakau, Mangamingi, Mangatainoka, Maoribank [3], Mapua [2], Marahau [2], Marewa, Marlborough, Martinborough [3], Marton [4], Masterton [9], Maungaraki [5], Mauriceville West, Maxwell [2], Melrose [5], Merivale [3], Middleton, Miramar [9], Moera, Monaco, Mornington [4], Motueka [11], Mount Cook [5], Mount Pleasant, Mount Victoria [8], Murchison [2], Naenae [8], Nelson [24], Nelson East [6], Nelson South [3], New Brighton, New Plymouth [9], Newlands [7], Newtown [23], Ngaio [11], Normanby, Normandale, Norsewood, Northland [11], Oakura, Ohura, Okaramio, Okiwi Bay, Opawa, Opiki, Opunake, Oriental Bay [2], Otaihanga, Otaki [4], Owhiro Bay, Paekakariki, Pakawau, Palmerston North [25], Papakowhai [5], Papanui, Paparangi [2], Paraparaumu [17], Paraparaumu Beach [13], Paremata [5], Parklands, Pauatahanui [3], Peka Peka, Petone [6], Picton [7], Pinehaven [3], Plimmerton [4], Pohara [2], Point Howard, Porirua [2], Porirua East [3], Porirua Harbour (Pauatahanui Arm), Port Nelson [2], Pukerua Bay, Rangataua, Rangihaeata, Rangiora [2], Rangitumau, Rarangi, Raroa, Raumati Beach [9], Raumati South [9], Redwood [2], Redwoodtown, Renwick [2], Riccarton [6], Richmond [12], Riwaka [2], Rongotai, Ruby Bay [3], Saint Albans [2], Saint Martins [2], Seatoun Heights, Shannon [2], Shirley, Silverstream [2], Solway, Somerfield [2], Spotswood, Spreydon [3], Spring Creek,Springlands [5], Springvale, Stoke [15], Stokes Valley [7], Strandon, Stratford [5], Strathmore Park, Sumner [2], Sydenham, Tahunanui [4], Taihape, Takaka [4], Taradale [2], Tasman [3], Taumarunui [2], Tauranga, Tawa [20], Te Horo, Te Horo Beach, Te Marua, Te Puke, Tennyson Inlet, Terrace End [2], The Pines Beach, Timberlea [3], Titahi Bay [7], Totara Park [3], Trentham [4], Tuamarina, Tukurua Point, Turitea, Upper Hutt [15], Upper Moutere, Upper Takaka, Urenui, Vogeltown, Wadestown [6], Waikanae [7], Waikanae Beach [9], Wainuiomata [11], Wainuioru, Waitara [4], Waitarere, Waitaria Bay, Waituna West, Waiwhetu [5], Wakapuaka, Wakatu, Wakefield, Wallaceville [2], Wanganui [10], Wanganui East [6], Washington Valley, Waterloo [4], Wellington [99], Westmere, Westown [3], Westport [2], Whangaehu, Whitby [15], Whitecliffs, Wilton [7], Woburn [4], Woodbourne, Woodville [2], Woolston [4].
  
  
• MM 3 - "Felt indoors; hanging objects may swing, vibration similar to passing of light trucks, may not be recognised as an earthquake":
  Aranui, Manurewa East, Mount Eden, Paparangi, Springvale, Wellington, Westport.