Magnitude 7.7 – 199km ESE of Nikol’skoye, Russia and Magnitude 6.2 – 183km ESE of Nikol’skoye, Russia – July 17, 2017

July 18, 2017 by

USGS Event Page

Magnitude 6.6 – 198km NW of Auckland Island, New Zealand – July 11, 2017

July 12, 2017 by

“The eastern margin of the Australia plate is one of the most sesimically active areas of the world due to high rates of convergence between the Australia and Pacific plates. In the region of New Zealand, the 3000 km long Australia-Pacific plate boundary extends from south of Macquarie Island to the southern Kermadec Island chain. It includes an oceanic transform (the Macquarie Ridge), two oppositely verging subduction zones (Puysegur and Hikurangi), and a transpressive continental transform, the Alpine Fault through South Island, New Zealand.

Since 1900 there have been 15 M7.5+ earthquakes recorded near New Zealand. Nine of these, and the four largest, occurred along or near the Macquarie Ridge, including the 1989 M8.2 event on the ridge itself, and the 2004 M8.1 event 200 km to the west of the plate boundary, reflecting intraplate deformation. The largest recorded earthquake in New Zealand itself was the 1931 M7.8 Hawke’s Bay earthquake, which killed 256 people. The last M7.5+ earthquake along the Alpine Fault was 170 years ago; studies of the faults’ strain accumulation suggest that similar events are likely to occur again.” –USGS

Magnitude 5.8 – 11km SSE of Lincoln, Montana -AND- Magnitude 6.5 – 3km NNE of Masarayao, Philippines – July 6, 2017

July 7, 2017 by

The distance from Montana to Massachusetts is much closer than the distance from the Philippines to Massachusetts, hence the much larger amplitude seismic waves on our BC-ESP seismographs!!

USGS Event Page for Montana
Magnitude 5.8 – 11km SSE of Lincoln, Montana
2017-07-06 06:30:17 UTC
46.871°N   -112.603°W
13.6 km depth
USGS Tectonic Summary for Montana earthquake:
“The July 6, 2017 M 5.8 earthquake southeast of Lincoln in western Montana occurred as the result of shallow strike slip faulting. The location and focal mechanism solution of this earthquake are consistent with right-lateral faulting in association with faults of the Lewis and Clark line, a prominent zone of strike-slip, dip slip and oblique slip faulting trending east-southeast from northern Idaho to east of Helena, Montana, southeast of this earthquake. In the region of the July 6th earthquake, prominent faults include the St Mary’s-Helena Valley fault, and the Bald Butte fault, both right-lateral structures. More detailed field studies will be required to identify the causative fault responsible for this earthquake.”

USGS Event Page for Philippines
Magnitude 6.5 – 3km NNE of Masarayao, Philippines
2017-07-06 08:03:57 UTC
11.114°N   124.633°E
6.5 km depth
USGS Tectonic Summary for Philippines earthquake:
“The Philippine Sea plate is bordered by the larger Pacific and Eurasia plates and the smaller Sunda plate. The Philippine Sea plate is unusual in that its borders are nearly all zones of plate convergence. The Pacific plate is subducted into the mantle, south of Japan, beneath the Izu-Bonin and Mariana island arcs, which extend more than 3,000 km along the eastern margin of the Philippine Sea plate. This subduction zone is characterized by rapid plate convergence and high-level seismicity extending to depths of over 600 km. In spite of this extensive zone of plate convergence, the plate interface has been associated with few great (M>8.0) ‘megathrust’ earthquakes. This low seismic energy release is thought to result from weak coupling along the plate interface (Scholz and Campos, 1995).