Hi Kevin, Thanks for that presentation, it really helps to explain the way EQ's result from the rock breaking.
Now there has been a bit more time to assess the two faults, is there any concern that the unruptured section between the Greendale and Lyttleton faults could also rupture in the near future?
Even though it was smaller its location relative to Christchurch resulted in more damage and higher ground accelerations. Also, there will have been a number of buildings which were weakened by the M 7.1 September earthquake and last weeks earthquake will have been enough to completely collapse them. The Richter scale is logarithmic and September earthquake released about 10 times as much energy as the February earthquake.
The fault for the Feb. 22 quake is not the same fault as the Greendale Fault which ruptured during the Sept. earthquake. They are not physically connected; however, the September earthquake did trigger last week’s earthquake. The Alpine Fault runs along the west coast of the South Island and is a separate fault to any faults in Canterbury. The stress build up is part of the normal interaction between the Pacific and Australian plates which causes all of the built up stresses in New Zealand.
The fault for the Feb. 22 quake is not the same fault as the Greendale Fault which ruptured during the Sept. earthquake. They are not physically connected; however, the September earthquake did trigger last week’s earthquake. The Alpine Fault runs along the west coast of the South Island and is a separate fault to any faults in Canterbury. The stress build up is part of the normal interaction between the Pacific and Australian plates which causes all of the built up stresses in New Zealand.
Useful presentation. Does GNS have a 3D or even a 2D image representation of the blocks of crust that have moved during the September and Feb quakes. while the fault lines are somewhat useful, I would imagine that you could do some extrapolation to other known faults to give a "best guestimate" of the underlying "blocks". It would be most enlightening to the average viewer and would make excellent TV presentation to explain what actually happened and that it is "expected".
hello i study geology at auckland; is the current earthquake from the same fault line as the september line? Also is the faulting activity seen over the last 6 months considered to be operating under the main alpine fualt zone, or seperatly and if so, any idears what caused the stress build up?
How is energy measured in a quake? This recent quake was obviously smaller on the Reichter scale yet far more damaging. Is reichter a (log) scale of amplitude? If so, is there a measure for acceleration? I heard the earlier shake exerted 0.8g (I guess horizontally?) and the recent quake exerted 1g? Is it the magnitude of acceleration change which does the damage? How else to explain the greater damage of a 'smaller' quake. Thanks, S
@UnkleSi Energy is measured on 2 main scales, the richter scale wich is a raw discription of a energy relsease and yes its on a log scale. 7.1 is almost x10 the strength of the 6.4. The other scale is the mercalli intensity scale, measureing damage done. This is applicable in this situation due to the vastly diffrent damage. Many other factors than the magnitude effect this though. Depth of focal point (was shallower), proximity to the city (closer), also what rock it passes through.
@UnkleSi Most of canterbury is made of reletivly unconsolidated rock and silts, and this amplifies any subsurface wave energy, makeing the surface effet alot worse. Dont quote me on this but the recent quake may have seen a much more unconslidated area of land being directly effected.
Calculating energy release in an earthquake involves a great deal more than simply measuring the amplitude on seismograms, but it is routinely done. It requires precise modelling of the seismograms and fairly involved calculations. The main reason that the February earthquake caused far more damage in Christchurch than the September earthquake is that the February earthquake was located much closer to Christchurch, and also somewhat shallower.
8kms!! Wow! Thanks Kevin for the great explanation. I've heard so much 'woo' this week about someone's friends friend who is predicting more quakes on another date... It's great to get the science out there. Well done. ps. no need to 'approve' comments on youtube, it's annoying for commenter, just comment on the comments or remove them if they are offensive etc. thanks.
8kms!! Wow! Thanks Kevin for the great explanation. I've heard so much 'woo' this week about someone's friends friend who is predicting more quakes on another date... It's great to get the science out there. Well done.
@gebbdub The seismic wave velocities are variable depending on the density and elasticity of the rock they are traveling through. P waves propagate at up to about 8 kms per second, whilst S waves travel at about 60% of the P wave velocity
Hi Kevin, Thanks for that presentation, it really helps to explain the way EQ's result from the rock breaking.
Now there has been a bit more time to assess the two faults, is there any concern that the unruptured section between the Greendale and Lyttleton faults could also rupture in the near future?
JakobusVdL 10 months ago
Even though it was smaller its location relative to Christchurch resulted in more damage and higher ground accelerations. Also, there will have been a number of buildings which were weakened by the M 7.1 September earthquake and last weeks earthquake will have been enough to completely collapse them. The Richter scale is logarithmic and September earthquake released about 10 times as much energy as the February earthquake.
GNSscience 1 year ago
The fault for the Feb. 22 quake is not the same fault as the Greendale Fault which ruptured during the Sept. earthquake. They are not physically connected; however, the September earthquake did trigger last week’s earthquake. The Alpine Fault runs along the west coast of the South Island and is a separate fault to any faults in Canterbury. The stress build up is part of the normal interaction between the Pacific and Australian plates which causes all of the built up stresses in New Zealand.
GNSscience 1 year ago
The fault for the Feb. 22 quake is not the same fault as the Greendale Fault which ruptured during the Sept. earthquake. They are not physically connected; however, the September earthquake did trigger last week’s earthquake. The Alpine Fault runs along the west coast of the South Island and is a separate fault to any faults in Canterbury. The stress build up is part of the normal interaction between the Pacific and Australian plates which causes all of the built up stresses in New Zealand.
GNSscience 1 year ago
Useful presentation. Does GNS have a 3D or even a 2D image representation of the blocks of crust that have moved during the September and Feb quakes. while the fault lines are somewhat useful, I would imagine that you could do some extrapolation to other known faults to give a "best guestimate" of the underlying "blocks". It would be most enlightening to the average viewer and would make excellent TV presentation to explain what actually happened and that it is "expected".
JaguarAJ6 1 year ago
hello i study geology at auckland; is the current earthquake from the same fault line as the september line? Also is the faulting activity seen over the last 6 months considered to be operating under the main alpine fualt zone, or seperatly and if so, any idears what caused the stress build up?
nickoswoos 1 year ago
Hi Kevin,
How is energy measured in a quake? This recent quake was obviously smaller on the Reichter scale yet far more damaging. Is reichter a (log) scale of amplitude? If so, is there a measure for acceleration? I heard the earlier shake exerted 0.8g (I guess horizontally?) and the recent quake exerted 1g? Is it the magnitude of acceleration change which does the damage? How else to explain the greater damage of a 'smaller' quake. Thanks, S
UnkleSi 1 year ago
@UnkleSi Energy is measured on 2 main scales, the richter scale wich is a raw discription of a energy relsease and yes its on a log scale. 7.1 is almost x10 the strength of the 6.4. The other scale is the mercalli intensity scale, measureing damage done. This is applicable in this situation due to the vastly diffrent damage. Many other factors than the magnitude effect this though. Depth of focal point (was shallower), proximity to the city (closer), also what rock it passes through.
nickoswoos 1 year ago
@UnkleSi Most of canterbury is made of reletivly unconsolidated rock and silts, and this amplifies any subsurface wave energy, makeing the surface effet alot worse. Dont quote me on this but the recent quake may have seen a much more unconslidated area of land being directly effected.
nickoswoos 1 year ago
Calculating energy release in an earthquake involves a great deal more than simply measuring the amplitude on seismograms, but it is routinely done. It requires precise modelling of the seismograms and fairly involved calculations. The main reason that the February earthquake caused far more damage in Christchurch than the September earthquake is that the February earthquake was located much closer to Christchurch, and also somewhat shallower.
GNSscience 1 year ago
8kms!! Wow! Thanks Kevin for the great explanation. I've heard so much 'woo' this week about someone's friends friend who is predicting more quakes on another date... It's great to get the science out there. Well done. ps. no need to 'approve' comments on youtube, it's annoying for commenter, just comment on the comments or remove them if they are offensive etc. thanks.
UnkleSi 1 year ago
8kms!! Wow! Thanks Kevin for the great explanation. I've heard so much 'woo' this week about someone's friends friend who is predicting more quakes on another date... It's great to get the science out there. Well done.
UnkleSi 1 year ago
How fast do waves travel through the ground?
gebbdub 1 year ago
@gebbdub The seismic wave velocities are variable depending on the density and elasticity of the rock they are traveling through. P waves propagate at up to about 8 kms per second, whilst S waves travel at about 60% of the P wave velocity
GNSscience 1 year ago