User:Kdowde3/sandbox

= Background =

The Santa Cruz and Solomon Islands are located on the plate boundary between the Australian and Pacific plate. This highly seismic region has “near 90° bend in the boundary…" This area experiences much plate movement as the Santa Cruz Island “has upper plate strike-slip and normal faulting, plate boundary under-thrusting, outer rise extensional faulting, and intraplate faulting” and the Solomon Islands are located on the subduction zone of the two boundaries. On February 6, 2013, the largest under-thrusting earthquake ever to be recorded in that area caused a tsunami and both were destructive to the area. Major villages on both groups of islands, Lata and Nendö were destroyed and at least 724 homes were confirmed as damaged.

= Geographic Information =

The earthquake was formed on the boundary between the Pacific and Australian plates. This area has very complicated faulting patterns that are very close to the Solomon Island arcs and Vanuatu Island arcs. The area is used to high frequency, low to moderate intensity seismic activity. However, many of the “larger events recorded have involved intraplate and interplate earthquakes with magnitudes up to about 8.0, several of which were located near the abrupt bends in the arcs. The Solomon Islands appear to have more seismic activity than the other areas earthquake productivity than most areas. The area also seems to produce more earthquake “doublets” and “triplets,” a deviation from the normal earthquake aftershock in which a second and sometimes third earthquake can be produced from the aftershock of the first earthquake. This occurs rarely, maybe once or twice a year, making this area a unique seismic area.

= The Event =

A magnitude 8.0 earthquake struck near the Santa Cruz Islands along the northern end of the Vanuatu subduction zone on February 6, 2013. “This event had a shallow dipping thrust faulting mechanism…” and “…produced a tsunami of ~ 1.5 height” on the Santa Cruz Islands. This is the largest regional event in the seismological record dating back to about 1900 and there is no record of large tsunami ever hitting the area after similar sized events. Toward the end of the week before February 6, the area was very active and there were many magnitude 6 earthquakes that occurred in the area. Originally, the earthquake was reported as a magnitude 6, which would not be a cause for concern in this area as it was unlikely that a tsunami would form. However, more information came in, determining that the earthquake was about a magnitude 8 causing extreme tsunami warnings for the area. The closest island to the epicenter, Nendo and it’s largest city, Lata were said to experience the largest amount of shaking. Even though there were aftershock earthquakes of magnitude 6, the most worrisome affect of the hurricane was the potential tsunami.As the wait for the tsunami continued, many villages had already been destroyed. For example, the massive earthquake destroyed many villages to the west and south of Lata, on the coastline, before the tsunami had even arrived. Many Pacific countries had ordered evacuations, as their authorities did not have to take any risks. Even countries that were not on the warning list were being evacuated. Residents of the Solomon Islands and other surrounding islands were working their way to higher ground. Major traffic jams were caused in Honiara, the capital city of Solomon Islands as people were attempting to get away from the coming wave. After “the mainshock, the epicenter area was hit by 13 aftershocks greater than magnitude 5.”

= The Ecosystem = 85% of the people on these islands live a subsistence lifestyle. That means that major loss of biodiversity, like that caused by both the earthquake and tsunami, can lead to “hunger, poverty, disease, and conflict and is a threat to internal security…” to both islands. The ecosystems in both of these islands are already being threatened by things invasive species, major loss of costal land, and overharvesting. This is because the population is slowly growing and they need more resources to survive. The population is growing about 4.4% annually and as it grows, they people must use more of their natural resources as food and shelter. There are many human elements that affect the ecosystem and how both the Santa Cruz and Solomon Islands will recover from the natural disasters. Firstly, both sets of islands are guilty of destroying their land by overharvesting and slowly depleting their biodiversity. Thought it was once one of the most diverse ecosystems in the world, very little attention is given to biodiversity and environmental conservation.

= References =