2016 Solomon Islands earthquakes#December 17 earthquake

{{Infobox earthquake

| name = 8 December 2016 Solomon Islands earthquake

| duration = >1 minute

| alt =

| caption =

| map =

| map_alt =

| map_caption =

| location = {{Coord|10.681|S|161.327|E|format=dms|type:event_dim:200km |display=inline,title}}

| map2 =

| timestamp = 2016-12-08 17:38:46

| isc-event = 611831246

| anss-url = us20007z80

| local-date = 9 December 2016

| local-time = 04:38

| image = M 7.8 - 69km WSW of Kirakira, Solomon Islands.jpg

| depth = 40.0 km

| magnitude = 7.8 {{M|ww|link=yes}}

| fault = San Cristobal-New Britain Trench

| type = Oblique-reverse

| affected =

| damages = 1000+ buildings damaged or destroyed

| intensity = {{MMI|8}}

| pga =

| pgv =

| tsunami = 0.43 metres

| landslide = Yes

| foreshocks =

| aftershocks = {{M|ww|link=yes}} 6.5
{{M|ww|link=yes}} 6.9

| casualties = 1 dead

| citations =

}}

On 9 December 2016 at 4:38 a.m. (UTC +11) local time (17:38:46 UTC), the Solomon Islands region was rocked by an {{M|ww}}7.8 earthquake, centred 30 km off San Cristobal Island, about 61 km southwest of Kirakira, the capital of Makira-Ulawa Province.{{Cite news|agency=Reuters|date=9 December 2016|title=Solomon Islands Earthquake Triggers Tsunami Alert In South Pacific|work=NDTV|url=https://www.ndtv.com/world-news/magnitude-7-7-earthquake-hits-solomon-islands-region-at-risk-of-tsunami-1635744|access-date=1 December 2020}} Initially registering magnitude 8.0, later downgraded to 7.8, the temblor prompted tsunami warnings that kept countries surrounding the Coral, Tasman and Solomon Sea on high alert, but was later cancelled. A large aftershock of magnitude 6.9 occurred shortly afterwards. This earthquake was largely felt, waking many residents who later ran to high ground for fears of a potential tsunami.{{Cite news|date=9 December 2016|title=Magnitude 7.8 quake hits off Solomons|work=RNZ|url=https://www.rnz.co.nz/international/pacific-news/319981/magnitude-7-point-8-quake-hits-off-solomons|access-date=1 December 2020}} The earthquake killed a child and affected some 34,000 people in Makira, South Malaita and Guadalcanal Island where many had lost their homes or had no access to basic needs.{{Cite web|last=Reid|first=Kathryn|date=21 August 2018|title=Solomon Islands: Earthquakes, tsunamis, volcanoes, and floods|url=https://www.worldvision.org/disaster-relief-news-stories/solomon-islands-earthquakes-tsunamis-volcanoes-floods-facts#:~:text=How%20damaging%20was%20the%202016%20Solomon%20Islands%20earthquake%3F,-The%20Solomon%20Islands&text=A%20magnitude%207.8%20undersea%20earthquake,capital%20of%20Makira%2DUlwara%20Province.&text=People%20fled%20to%20higher%20ground,for%20fear%20of%20a%20tsunami.|access-date=1 December 2020|website=World Vision}} Earthquakes are common in this region, with little or no fatalities. This earthquake is tied with three other magnitude 7.8 earthquakes for the second largest earthquake of 2016.{{Cite news|last=Breslin|first=Sean|date=8 December 2016|title=7.8 Earthquake Strikes Solomon Islands; Tsunami Watch Canceled for Hawaii|work=The Weather Channel|url=https://weather.com/news/news/solomon-islands-earthquake|access-date=1 December 2020}} On 17 December, Solomon Islands would be rattled again by a 7.9 magnitude earthquake, this time 54 km east of Taron, Papua New Guinea.{{cite web|title=M 7.9 - 54km E of Taron, Papua New Guinea|url=https://earthquake.usgs.gov/earthquakes/eventpage/us200081v8/executive|website=USGS-ANSS|publisher=USGS|access-date=21 March 2021}}

Geological setting

The Australian Woodlark, Solomon Sea and Pacific plates are converging at a rate of 97 mm/yr.{{Cite journal|last=Kaustubh Thirumalai, Frederick W. Taylor, Chuan-Chou Shen, Luc L. Lavier, Cliff Frohlich, Laura M. Wallace, Chung-Che Wu, Hailong Sun & Alison K. Papabatu|date=30 June 2015|title=Variable Holocene deformation above a shallow subduction zone extremely close to the trench|url=https://www.researchgate.net/publication/279629789|journal=Nature Communications|volume=6|page=7607|doi=10.1038/ncomms8607|pmid=26123872|pmc=4491809|bibcode=2015NatCo...6.7607T|s2cid=8275538|doi-access=free}} The earthquake was a result of interaction between the Australian and Pacific plates along a subduction zone. Subduction of the Australian Plate has also given rise to volcanoes in the region. This region of the world lies along the Pacific Ring of Fire, where 90 percent of all earthquake and volcanic activity is concentrated here.{{Cite news|last=Hanna, O'Sullivan|first=Jason, Donnie|date=8 December 2016|title=Solomon Islands tsunami threat over after 7.8 quake|work=CNN|url=https://edition.cnn.com/2016/12/08/asia/solomon-islands-earthquake/index.html|access-date=1 December 2020}}

Earthquake

The earthquake occurred along the boundary interface where the Australian and Pacific Plates make contact. Focal mechanism suggests this event was a result of oblique-reverse faulting.{{Cite web|title=M 7.8 – 69km WSW of Kirakira, Solomon Islands|url=https://earthquake.usgs.gov/earthquakes/eventpage/us20007z80/executive|access-date=1 December 2020|website=US Geological Survey}} The earthquake did not rupture to the trench, terminating at a depth of 20 km, with its epicenter at 40 km. An average slip has been estimated at 5 meters.{{Cite web|title=Solomon Islands Tsunami on Dec. 8, 2016|url=https://iisee.kenken.go.jp/staff/fujii/Solomon2016/tsunami.html|access-date=1 December 2020}} The earthquake may also be a deep compressional intraslab event occurring on a fault located within the subducting plate; known as intraplate earthquakes because they happen in a plate rather than at the boundary of two.{{cite journal|author1=Lingling Ye|author2=Thorne Lay|authorlink2=Thorne Lay|author3=Hiroo Kanamori|authorlink3=Hiroo Kanamori|title=The 25 March 2020 MW 7.5 Paramushir, northern Kuril Islands earthquake and major (MW ≥ 7.0) near-trench intraplate compressional faulting|journal=Earth and Planetary Science Letters|date=2021|volume=556|issue=116728|page=116728|doi=10.1016/j.epsl.2020.116728|bibcode=2021E&PSL.55616728Y|s2cid=233944154|doi-access=free}}

= Tsunami =

The main earthquake triggered tsunami warnings directed at Solomon Islands, Vanuatu, Papua New Guinea, Nauru, New Caledonia, Tuvalu and Kosrae in the Federated States of Micronesia, issued by the Pacific Tsunami Warning Center. In New Caledonia, people were ordered to evacuate and leave for higher ground. Warnings for American Samoa and Hawaii were cancelled shortly after.{{Cite news|date=8 December 2016|title=Large earthquake strikes off Solomon Islands|work=DW|url=https://www.dw.com/en/large-earthquake-strikes-off-solomon-islands/a-36699408|access-date=1 December 2020}} The [http://itic.ioc-unesco.org/index.php International Tsunami Information Center] warned of tsunamis between 1 and 3 meters. However, the highest waves were measured at only 0.43 meters (1.41 feet) on Marika Island.{{Cite web|title=Tsunami Event Information SOLOMON ISLANDS|url=https://www.ngdc.noaa.gov/hazel/view/hazards/tsunami/event-more-info/5630|access-date=1 December 2020|website=NOAA NCEI}}

= Aftershocks =

A 6.5 magnitude earthquake struck about four hours after the initial quake, and later a 6.9 one day after the mainshock.{{Cite web|title=M 6.5 – 79km WSW of Kirakira, Solomon Islands|url=https://earthquake.usgs.gov/earthquakes/eventpage/us20007zbn/executive|access-date=1 December 2020|website=US Geological Survey}}{{Cite web|title=M 6.9 – 92km WSW of Kirakira, Solomon Islands|url=https://earthquake.usgs.gov/earthquakes/eventpage/us20007zlq/executive|access-date=1 December 2020|website=US Geological Survey}} The 6.9 aftershock prompted new tsunami warnings with forecasted waves of 0.30 meters (0.98 feet).{{Cite news|date=10 December 2016|title=Solomon Islands recover from 7.8-magnitude quake amid continuing aftershocks|work=National Thailand|url=https://www.nationthailand.com/news/30301852|access-date=1 December 2020}}

Aftermath

Phone and electricity lines were cut-off throughout the country in the immediate aftermath.{{Cite news|date=8 December 2016|title=Solomon Islands tsunami warning lifted after powerful 7.8 quake|work=BBC|url=https://www.bbc.com/news/world-asia-38257353|access-date=1 December 2020}} On Malaita Island, there were reports that between 35 and 40 buildings had been damaged.{{Cite news|date=9 December 2016|title=Damage assessment after M7.8 earthquake in Solomon Islands|work=The Watchers|url=https://watchers.news/2016/12/09/solomon-islands-earthquake-damage-december-2016/|access-date=1 December 2020}} In Guadalcanal, the collapse of a home killed one person.{{Cite web|title=Solomon Islands: Earthquake – Dec 2016|url=https://reliefweb.int/disaster/eq-2016-000128-slb|access-date=1 December 2020}} In Kirakira, many homes, a hospital, a church, and the World Vision office sustained serious damage.{{Cite web|title=Significant Earthquake Information|url=https://www.ngdc.noaa.gov/hazel/view/hazards/earthquake/event-more-info/10218|access-date=1 December 2020|website=NOAA NCEI}} Damage at the hospital forced the evacuation of 20 people.{{Cite news|last=Perry|first=Nick|date=9 Dec 2016|title=World Vision says hundreds affected by Solomon Islands quake|work=PhysOrg|url=https://phys.org/news/2016-12-world-vision-hundreds-affected-solomon.html|access-date=2 Dec 2020}} Two schools in Marika and Ugi were completely destroyed. Fissures and landslides were also seen in the affected region.{{Cite web|last=Westbrook, Greenfield|first=Tom, Charlotte|date=9 December 2020|title=Residents take to the hills as powerful quake hits Solomon Islands|url=https://in.reuters.com/article/quake-solomon-islands-idINKBN13X26Y|archive-url=https://web.archive.org/web/20161208194907/http://in.reuters.com/article/quake-solomon-islands-idINKBN13X26Y|url-status=dead|archive-date=8 December 2016|access-date=1 December 2020|website=Reuters}} People who fled to higher ground continued to stay on the hills for fears of a large tsunami. Twenty-five houses were washed away from the moderate tsunami.{{Cite news|last=WESTBROOK, GREENFIELD|first=TOM, CHARLOTTE|date=9 Dec 2020|title=Residents Take to the Hills as Powerful Quake Hits Solomon Islands|work=JakartaGlobe|url=https://jakartaglobe.id/news/residents-take-hills-powerful-quake-hits-solomon-islands/|access-date=2 Dec 2020}} In total, over 1000 homes were damaged, along with 20 schools and four clinics.{{Cite web|date=1 June 2017|title=Six months on after Solomon Islands' 7.8 magnitude earthquake|url=https://www.wvi.org/article/six-months-after-solomon-islands-78-magnitude-earthquake|access-date=1 December 2020|website=World Vision}} More than 9,769 people were affected by the earthquake.{{cite web|author1=International Federation of Red Cross and Red Crescent Societies|title=Solomon Island: Earthquake Emergency Plan of Action (EPoA) DREF operation no MDRSB006|url=https://reliefweb.int/report/solomon-islands/solomon-island-earthquake-emergency-plan-action-epoa-dref-operation-no|publisher=ReliefWeb|access-date=29 March 2022|date=24 December 2016}}

= International reaction =

Julie Bishop, the Australian foreign minister at the time said that the country is prepared to offer their support to Solomon Islands.{{Cite news|last=Hardy|first=Catherine|date=9 December 2016|title=Australia "ready to help" quake-hit Solomons|work=euronews|url=https://www.euronews.com/2016/12/09/magnitude-77-earthquake-off-solomon-islands-usgs-risk-of-tsunami-waves-along-coasts-of-solomon-islands-vanuatu-papua-new-guinea-nauru-new-caledonia-tuvalu-and-kosrae|access-date=1 December 2020}}

17 December earthquake

{{Infobox earthquake

| name = 17 December 2016 Solomon Islands earthquake

| location = {{Coord|4.505|S|153.522|E|format=dms|type:event_dim:200km}}

| map2 = {{Location map | Papua New Guinea

| relief = yes

| label =

| lat = -4.505

| long = 153.522

| mark = Bullseye1.png

| marksize = 50

| position = bottom

| width = 260

| float = right

| caption =

}}

| timestamp = 2016-12-17 10:51:10

| isc-event = 611831311

| anss-url = us200081v8

| local-time = 20:51

| magnitude = 7.9 {{M|w|link=yes}}

| depth = {{Convert|94.5|km|abbr=on}}

| type = First subevent reverse

Second subevent thrust

| intensity = {{MMI|VII}}{{Cite web|title=M 7.9 - 54km E of Taron, Papua New Guinea|url=https://earthquake.usgs.gov/earthquakes/eventpage/us200081v8/pager|website=earthquake.usgs.gov|access-date=15 December 2021}}

| tsunami = {{Cvt|1.25|m|ft}}{{Cite web|title=M 8 Earthquake and Tsunami (1.2 m) in Papua New Guinea from 17 Dec 2016 10:51 UTC to 10:51|url=https://www.gdacs.org/Tsunamis/report.aspx?eventid=1101099&episodeid=1150868&eventtype=EQ|work=Global Disaster Alert and Coordination System}}

| casualties = None

| local-date = 17 December 2016

}}

On 17 December, the largest earthquake in the year 2016, a magnitude 7.9 earthquake struck Papua New Guinea. It was centred between the islands of New Ireland and Bougainville. The earthquake did not cause any major damage or casualties but did result in power outages.{{cite news|title=Papua New Guinea earthquake: Residents flee to hills after magnitude-7.9 quake, tsunami threat passes|url=https://www.abc.net.au/news/2016-12-17/powerful-earthquake-hits-off-coast-of-papua-new-guinea/8129790|access-date=21 March 2021|agency=ABC.net.au|publisher=ABC News|date=17 December 2016}}

The earthquake had an intermediate depth of 94.5 km beneath the surface. The initial event was a result of reverse faulting within a subducting oceanic lithosphere which lasted for 30 seconds.{{cite journal|last=Lay|first=Thorne|last2=Ye|first2=Lingling|last3=Ammon|first3=Charles J.|last4=Kanamori|first4=Hiroo|title=Intraslab rupture triggering megathrust rupture coseismically in the 17 December 2016 Solomon Islands Mw 7.9 earthquake|journal=Geophysical Research Letters|year=2017|volume=44|issue=3|pages=1286–1292|issn=0094-8276|doi=10.1002/2017GL072539|bibcode=2017GeoRL..44.1286L|doi-access=free|url=https://authors.library.caltech.edu/75347/1/Lay_et_al-2017-Geophysical_Research_Letters.pdf}} After the intraslab rupture, a deep portion of the subduction zone began to slip at a depth of 32 to 47 km, releasing energy comparable to the first event. The shallow megathrust rupture was evident in the large number of shallow aftershocks. Due to the two separate events occurring closely in timing and location, it was considered a doublet earthquake.