31.03.2009 (revised) « New Zealand Earthquake Review 2009

31.03.2009 (revised)

New Zealand Earthquakes March 31st 2009
Revised Data 57 Events 1.421ML to 5.02ML
(updated 15.05.2009)
REF, LAT, LONG, TIME, DEPTH, MAG, FELT
3068027, -40.13175, 174.87152, 2009/03/31 00:01:27.9, 12, 2.018
3068029, -39.81696, 174.45465, 2009/03/31 00:08:28.1, 105.2, 2.55
3068030, -39.0899, 177.54042, 2009/03/31 00:11:10.2, 27.6, 2.349
3068031, -41.70824, 172.21362, 2009/03/31 00:15:40.7, 5, 2.199
3068045, -40.08109, 176.38841, 2009/03/31 01:05:15.9, 27.7, 2.334
3068060, -40.07417, 176.38138, 2009/03/31 01:43:39.6, 33.8, 2.029
3068062, -37.82793, 176.66656, 2009/03/31 01:44:43.8, 5, 1.809
3068099, -41.49909, 172.888, 2009/03/31 03:28:19.0, 124, 4.554, F
3068118, -44.25416, 170.0473, 2009/03/31 04:16:27.4, 18.5, 2.147
3068156, -42.32931, 172.89183, 2009/03/31 05:59:07.4, 28.8, 1.939
3068159, -42.99581, 171.46745, 2009/03/31 06:07:35.8, 5, 2.701
3068162, -39.21812, 174.74684, 2009/03/31 06:14:20.4, 32.2, 2.396
3068164, -41.12441, 174.67543, 2009/03/31 06:19:55.3, 31, 2.267
3068170, -45.06385, 167.6208, 2009/03/31 06:40:06.9, 112.3, 2.425
3068181, -42.08938, 173.14581, 2009/03/31 07:11:59.5, 5, 2.51
3068185, -44.94066, 167.38847, 2009/03/31 07:24:20.4, 12, 2.196
3073780, -40.53796, 176.50046, 2009/03/31 07:27:09.6, 24.5, 1.723
3068207, -42.99014, 171.45941, 2009/03/31 08:35:39.5, 5, 2.016
3068211, -38.26967, 176.64307, 2009/03/31 08:46:49.6, 71.2, 2.603
3073785, -41.11357, 173.4324, 2009/03/31 08:47:41.4, 75.8, 2.403
3068212, -40.49514, 174.7531, 2009/03/31 08:49:26.6, 34.7, 2.129
3068217, -40.25097, 176.04843, 2009/03/31 09:06:22.6, 28.9, 2.252
3073786, -45.54121, 166.97659, 2009/03/31 09:06:47.3, 63.3, 2.262
3073789, -40.38056, 176.1109, 2009/03/31 09:22:34.7, 25.2, 2.139
3068226, -37.64008, 179.43433, 2009/03/31 09:22:59.1, 33, 3.243
3068229, -44.85651, 167.99187, 2009/03/31 09:32:04.5, 92.5, 2.219
3068252, -39.36475, 179.93582, 2009/03/31 10:39:48.6, 33, 3.524
3073798, -43.36738, 171.76784, 2009/03/31 10:44:26.1, 5, 2
3068253, -37.75663, 176.4248, 2009/03/31 10:45:59.4, 181.6, 5.02, F
3068255, -41.38583, 172.29514, 2009/03/31 10:51:54.8, 5, 2.05
3068274, -39.21362, 174.7628, 2009/03/31 11:47:05.4, 31.3, 2.147
3068277, -38.47871, 176.25566, 2009/03/31 11:55:55.9, 87.4, 2.739
3068287, -42.10853, 172.13988, 2009/03/31 12:20:00.0, 5, 2.666
3068291, -39.3203, 175.07693, 2009/03/31 12:29:56.7, 32.5, 2.26
3068308, -41.07746, 174.85275, 2009/03/31 13:15:16.8, 27.3, 1.955
3068312, -39.59447, 176.90266, 2009/03/31 13:27:22.2, 26.4, 2.344
3068322, -39.42642, 177.26013, 2009/03/31 13:48:07.3, 25.8, 2.18
3068330, -45.03004, 167.5365, 2009/03/31 14:07:46.5, 121.4, 2.657
3068336, -39.1457, 175.42815, 2009/03/31 14:31:04.4, 5, 1.545
3068348, -39.50314, 177.19679, 2009/03/31 14:54:02.3, 33, 2.417
3068372, -40.54214, 175.94649, 2009/03/31 15:41:50.2, 29.3, 1.713
3068384, -37.78447, 176.80234, 2009/03/31 16:08:03.5, 5, 1.997
3068388, -47.41619, 165.73767, 2009/03/31 16:17:13.5, 33, 2.62
3068394, -43.14251, 170.92963, 2009/03/31 16:36:25.0, 5, 1.685
3074135, -45.4021, 166.72171, 2009/03/31 16:37:33.1, 22.3, 2.284
3068395, -38.98896, 175.72923, 2009/03/31 16:40:39.0, 5, 1.421
3068406, -37.75589, 176.8653, 2009/03/31 17:15:56.7, 5, 2.486
3068439, -41.24666, 174.70744, 2009/03/31 18:56:57.6, 34.4, 2.296
3068447, -39.75888, 176.58511, 2009/03/31 19:21:54.0, 48.5, 2.514
3068460, -40.77546, 174.86281, 2009/03/31 19:51:42.6, 5, 2.645
3068468, -39.93802, 176.68573, 2009/03/31 20:03:18.8, 38.1, 2.435
3068491, -39.20045, 176.85268, 2009/03/31 21:02:08.0, 36.5, 2.204
3068498, -39.31084, 175.07008, 2009/03/31 21:14:59.0, 31.9, 2.244
3068503, -40.75024, 175.81557, 2009/03/31 21:25:10.9, 22.4, 2.018
3068510, -39.23916, 175.30898, 2009/03/31 21:49:08.3, 17.8, 1.792
3068526, -38.62458, 176.07016, 2009/03/31 22:27:19.5, 2, 2.033, F
3068538, -38.16359, 176.40933, 2009/03/31 22:54:42.2, 146, 3.13

data by geonet. maps by google earth. plots by highace using GPS Visualizer

GoogleEarth File

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Map Key

Earthquake Markers

On the daily maps each coloured dot or marker represents an earthquake, the colours indicate the size range. The largest quake of the day is marked with a number showing the size in ML.
Dots that are marked with a number and have a larger set of rings or a larger watermark around them are earthquakes that have been reported to Geonet as felt by the public.

Moon Phase key
Tidal forces act on rock as well as water. The earth's crust can rise and fall by as much as a metre - twice a day! - due to tidal forces. As the tidal deformation of the earth's crust is greatest at new and full moon, it is certainly plausible that earthquakes are more likely at these times. Lets find out!

As new revised data becomes available I have updated the data and the maps and (from July 1st) have added a box on each map showing the phase of the moon in the centre, the date in the upper left hand corner, the number of earthquakes in New Zealand that day (UTC) in the upper right hand corner and at the bottom the distance between the Moon and Wellington ( Lat -41.28, Long 174.78).
Note.
Currently the moon phases shown for July are the Northern Hemisphere view, which I will replace with the Southern Hemisphere view as time permits.
November moon phases are Southern Hemisphere view.

Data

Data used in creating these maps is sourced from GEONET

Earthquakes that have been reported as Felt by the public to Geonet through the Internet based GeoNet Felt Earthquake Reports are underlined or marked with an F on the daily list.
Further information about Felt quakes can be viewed by clicking the blue Comments link at the bottom of each post. Some recent posts have Felt Maps.
The intensity of the reports is scaled according to the
Modified Mercalli scale.

see information box further down page for description of the Modified Mercalli scale

Time

The days and hours, minutes and seconds posted in this blog are UTC time. This standard is "coordinated universal time", abbreviated UTC. This was formerly known as Greenwich mean time (GMT) Greenwich mean time was based upon the time at the zero degree meridian that crossed through Greenwich, England. GMT became a world time and date standard because it was used by Britain's Royal Navy and merchant fleet during the nineteenth century. Today, UTC uses precise atomic clocks, shortwave time signals, and satellites to ensure that UTC remains a reliable, accurate standard for scientific and navigational purposes. The New Zealand Time (NZST) is 12 hours ahead of UTC or 13 hours ahead during New Zealands Daylight Saving Time (NZDST) in the Summer.

NZ Seismic Background

Seismicity in New Zealand is dominated by the plate boundary. This boundary ( the thin blue line on the maps) runs down from the Tonga-Kermadec trench to the northeast of New Zealand, continues down the east coast of the North Island as the Hikurangi Trough, passes under the branch faulting systems of the Cook Strait-Marlborough Sounds region, and continues down the west coast of the South Island as the Alpine Fault. To the southwest of New Zealand it takes the form of the Puysegur Trench. Seismic activity is at its greatest to the northeast of the North Island. The Hikurangi Trough forms part of a westward-dipping subduction zone, the seismicity following the boundaries of the subducting plate down to depths of 300-400 km.

The seismicity also spreads out in a shallow belt (0-80 km) below the northeast-trending mountain ranges of the North Island and the Taupo Volcanic Zone behind them. (this is shown on the maps as the yellow "continental rift boundry", the red "transform fault" and the white " continental convergent boundry") The subduction zone continues below Cook Strait, but appears to come to an end, or at least the deeper earthquakes peter out, somewhere south of the Marlborough Sounds.

The northern part of the South Island, including the West Coast, has been among the most seismically active regions of New Zealand during this century; by contrast, the Alpine Fault itself, the major (transcurrent) fault accommodating plate motion in the South Island, has been seismically quiet. Seismic activity picks up rapidly in the Fiordland region and to the southwest of the South Island, and marks the beginning of a further, but eastward-dipping, subduction zone, with earthquakes recorded to depths of <200 km.

About 14,000 earthquakes, most of them minor, are recorded each year. About 200 of these are strong enough to be felt.

Modified Mercalli scale

May 2009
M	T	W	T	F	S	S
« Mar		Jun »
	1	2	3
4	5	6	7	8	9	10
11	12	13	14	15	16	17
18	19	20	21	22	23	24
25	26	27	28	29	30	31

The Modified Mercalli scale is designed to describe the effects of an earthquake, at a given place, on natural features, on industrial installations and on human beings. The intensity differs from the magnitude which is related to the energy released by an earthquake. There are multiple versions of the MM scale, the one listed here being the 1931 version.
MM I. Not felt - or, except rarely under especially favourable circumstances. Under certain conditions, at and outside the boundary of the area which a great shock is felt: sometimes birds, animals, reported uneasy or disturbed; sometimes dizziness or nausea experienced; sometimes trees, structures, liquids, bodies of water, may sway - doors may swing, very slowly.

MM II. Felt indoors by few, especially on upper floors, or by sensitive, or nervous persons. Also, as in grade I, but often more noticeably: sometimes hanging objects may swing, especially when delicately suspended; sometimes trees, structures, liquids, bodies of water, may sway, doors may swing, very slowly; sometimes birds, animals, reported uneasy or disturbed; sometimes dizziness or nausea experienced.

MM III. Felt indoors by several, motion usually rapid vibration. Sometimes not recognized to be an earthquake at first, duration estimated in some cases. Vibration like that due to passing of light, or lightly loaded trucks, or heavy trucks some distance away. Hanging objects may swing slightly. Movement may be appreciable on upper levels of tall structures. Rocked standing motor cars slightly.

MM IV. Felt indoors by many, outdoors by few. Awakened few, especially light sleepers. Frightened no one, unless apprehensive from previous experience. Vibration like that due to passing of heavy, or heavily loaded trucks. Sensation like heavy body striking building, or falling of heavy objects to inside. Rattling of dishes, windows, doors; glassware and crockery clink and clash. Creaking of walls, frame, especially in the upper range of this grade. Hanging objects swing, in numerous instances. Disturbed liquids in open vessels slightly. Rocked standing motor cars slightly.

MM V. Felt indoors by practically all, outdoors by many or most. Outdoors direction estimated. Awakened many, or most. Frightened few - slight excitement, a few ran outdoors. Buildings trembled throughout. Broke dishes, glassware, to some extent. Cracked windows - in some cases, but not generally. Overturned small or unstable objects, in many instances, with occasional fall. Hanging objects, doors, swing generally or considerably. Knocked pictures against walls, or swung them out of place. Opened or closed, doors, shutters, abruptly. Pendulum clocks stopped, started, or ran fast, or slow. Moved small objects, furnishings, the latter to slight extent. Spilled liquids in small amounts from well-filled open containers. Trees, bushes, shaken slightly.

MM VI. Felt by all, indoors and outdoors. Frightened many, excitement general, some alarm, many ran outdoors. Awakened all. Persons made to move unsteadily. Trees, bushes, shaken slightly to moderately. Liquid set in strong motion. Small bells rang -church, chapel, school etc. Damage slight in poorly built buildings. Fall of plaster in small amount. Cracked plaster somewhat, especially fine cracks chimneys in some instances. Broke dishes, glassware, in considerable quantity, also some windows. Fall of knick-knacks, books, pictures. Overturned furniture, in many instances. Moved furnishings of moderately heavy kind.

MM VII. Frightened all - general alarm, all ran outdoors. Some, or many, found it difficult to stand. Noticed by persons driving motor cars. Trees and bushes shaken moderately to strongly. Waves on ponds, lakes, and running water. Water turbid from mud stirred up. Incaving to some extent of sand or gravel stream banks. Rang large church bells, etc. Suspended objects made to quiver. Damage negligible in buildings of good design and construction, slight to moderate in well-build ordinary buildings, considerable in poorly build or badly designed buildings, abode houses, old walls (especially where laid up without mortar), spires, etc. Cracked chimneys to considerable extent, walls to some extent. Fall of plaster in considerable to large amount, also some stucco. Broke numerous windows, furniture to some extent. Shook down loosened brickwork and tiles. Broke weak chimneys at the roof-line (sometimes damaging roof. Fall of cornices from towers and high buildings. Dislodged bricks and stones. Overturned heavy furniture, with damage from breaking. Damage considerable to concrete irrigation ditches.

MM VIII. Fright general - alarm approaches panic. Disturbed persons driving motor cars. Trees shaken strongly - branches, trunks, broken off, especially palm trees. Ejected sand and mud in small amounts. Changes: temporary, permanent; in flow of springs and wells; dry wells renewed flow; in temperature of spring and well waters. Damage slight in structures (brick) built especially to withstand earthquakes. Considerable in ordinary substantial buildings, partial collapse: racked, tumbled down, wooden houses in some cases; threw out panel walls in frame structures, broke off decayed piling. Fall of walls. Cracked, broke, solid stone walls seriously. Wet ground to some extent, also ground on steep slopes. Twisting, fall, of chimneys, columns, monuments, also factory stack, towers. Moved conspicuously, overturned, very heavy furniture.

MM IX. Panic general. Cracked ground conspicuously. Damage considerable in (masonry) structure build especially to withstand earthquakes: threw out of plumb some wood-frame houses build especially to withstand earthquakes; great in substantial (masonry) buildings, some collapse in large part; or wholly shifted frame buildings off foundations, racked frames; serious to reservoirs; underground pipes sometimes broken.

MM X. Cracked ground, especially when loose and wet, up to widths of several inches; fissures up to a yard in width ran parallel to canal and stream banks. Landslides considerable from river banks and steep coasts. Shifted sand and mud horizontally on beaches and flat land. Changed level of water in wells. Threw water on banks of canals, lakes, rivers, etc. Damage serious to dams, dikes, embankments. Severe to well-build wooden structures and bridges, some destroyed. Developed dangerous cracks in excellent brick walls. Destroyed most masonry and frame structures, also their foundations. Bent railroad rails slightly. Tore apart, or crushed endwise, pipe lines buried in earth. Open cracks and broad wavy folds in cement pavements and asphalt road surfaces.

MM XI. Disturbances in ground many and widespread, varying with ground material. Broad fissures, earth slumps, and land slips in soft, wet ground. Ejected water in large amounts charged with sand and mud. Caused sea-waves ("tidal" waves) of significant magnitude. Damage severe to wood-frame structures, especially near shock centers. Great to dams, dikes, embankments, often for long distances. Few, if any (masonry), structures remained standing. Destroyed large well-built bridges by the wrecking of supporting piers, or pillars. Affected yielding wooden bridges less. Bent railroad rails greatly, and thrust them endwise. Put pipe lines buried in earthy completely out of service.

MM XII.Damage total - practically all works of construction damaged greatly or destroyed. Disturbances in ground great and varied, numerous shearing cracks. Landslides, falls of rock of significant character, slumping of river banks, etc. numerous and extensive. Wrenched loose, tore off, large rock masses. Fault slips in firm rock, with notable horizontal and vertical offset displacements. Water channels, surface and underground, disturbed and modified greatly. Dammed lakes, produced waterfalls, deflected rivers, etc. Waves seen on ground surfaces (actually seen, probably, in some cases). Distorted lines of sight and level. Threw objects upward into the air.

Source: Wood, H.O., and F. Neumann, 1931. Modified Mercalli Intensity Scale of 1931.
Bulletin of the Seismological Society of America, 21, 277-283.
Adapted from Sieberg's Mercalli-Cancani scale, modified and condensed.

New Zealand Earthquake Review 2009