The Feb 22nd earthquake in Christchurch was 6.3 on the Richter scale yet it did much more damage than the 7.1 earthquake on Sept 4th 2010. There are several reasons for this but the main ones are the depth of the epi-centre and the distance from the city. It was only 5km deep and very close to the city centre. We also know that much of the city is built on soft soil, especially part of the city near the epi-centre of the earthquake. Liquefaction in that soft soil caused a great deal of damage.
The Richter scale measures the energy of an earthquake. It is a logarithmic scale so a 4.0 earthquake is 10 times stronger than a 3.0 earthquake. The earthquake in Japan two days ago was 9.0 on the Richter scale. This is the largest earthquake that Japan has ever had. The epi-centre was 125 km off the east coast and 10km deep. This underwater earthquake started a tsunami. Tsunami is a Japanese word: “tsu” means harbour and “nami” means “wave”. It was this tsunami which caused so much damage and killed so many people.
The earthquake in Christchurch was not underwater. There was no tsunami at that time. However, high waves from the Japanese tsunami arrived in parts of the north and east in New Zealand yesterday.
Both New Zealand and Japan have many earthquakes. New Zealand is on the Australian and Pacific tectonic plate boundary. Japan is on the Ring of Fire.
After-shocks are common for the next few days, weeks, months or even a year after an earthquake. Christchurch has had many after-shocks since Sept 4th. The biggest one so far was 6.3 on Feb 22nd. Japan is continuing to have some very big after-shocks.
For see a record of NZ earthquakes or just Christchurch earthquakes, go to the Geonet website.
Grammar
Note the structure: “This is the largest earthquake that Japan has ever had.” The last verb is the part participle form. This is quite a difficult structure for English language learners but it is very common, especially when talking about your own experiences. Practise using it e.g. This is the hardest / easiest / most enjoyable / most frightening / best / worst /
+ noun
I have ever had / done / seen / eaten / tried.
Questions
How can countries prepare for earthquakes and tsunamis?
re:richter scale – i checked on wikipedia, it is logarithmic but a 4.0 is 31 times bigger than a 3.0, and a 5 is 1,000 (=31 x 31) times bigger than a 3. hence the one 9.0 in japan was 8,000 times bigger than the 6.3 in chch, with a difference of 2.7 units between the two.
I think the difference is whether you are measuring amplitude or energy. A word like “bigger” or “stronger” is not exact.