7.1 Magnitude Quake Strikes The Philippines

Dozens were dead, and many roads and buildings damaged when a 7.1 magnitude quake struck Bohol Island in the Philippines Tuesday morning. As many as 49 people so far have been confirmed dead, and up to 33 people were reported missing. Approximately 164 people were reported injured. The quake occurred about 20km deep underneath the island of Bohol, in the center of the Philippine archipelago, violently shaking Bohol island and neighboring (to the NW) Cebu island, while the rest of the islands felt moderate shaking. Many aftershocks of varying magnitudes are occurring and will likely continue for several weeks.

There are many nearby holocene volcanoes, some of which have shown historical activity. On the island of Negros I West of the epicenter, several volcanoes likely shook and could be destabilized by the quaking, including the Pleistocene to early Holocene Cuernos de Negros, Kanalon volcano, Mandalagan volcano, and Silay. Out of all of these volcanoes, only Kanalon volcano has had confirmed eruptions in historical time.

East of the epicenter, on the island of Leyte I, there are several volcanoes as well, including Cabalían, Mahagnao, and Biliran, all of which currently display fumerolic or geothermal activity, and all of which have had eruptive activity within the past two centuries.

                                    

Image from Google Earth with USGS quake shake map overlay, detailing the strength of the shake force around the Philippine archipelago and associated volcanoes.

Earthquakes this large can cause disruptions in magmatic systems. Although rarely will a volcano erupt directly after a large quake event, changes in pressures in the magma chambers, fractures in the mountains (which can cause landslides and other destabilization), and tectonic stress, can contribute over time to an increase in eruptive potential. While it is not an extreme danger at this point, monitoring on volcanoes near the epicenter would be a good proactive step to take in order to cover all of the bases.

The Philippines is home to many famous and dangerous volcanoes. In 1991, Mount Pinatubo, previously a rather unknown and unremarkable lava dome complex which was heavily forested, erupted violently, sending columns of ash skyward, and pyroclastic flows down its flanks, accompanied by deadly lahars. The eruption vented so much material into the atmosphere so quickly, that the ash circumnavigated the globe, and actually lowered global temperatures for about a year, effectively pausing the effects of global warming. This was the second largest eruption in the 20th century after Alaska's Novarupta event.

Mount Mayon is also quite an active volcano in the Philippines, having had many frequent eruptive episodes throughout history. Currently, no volcanoes except Mayon are displaying eruptive activity, but Taal volcano in Luzon has been showing unrest in recent years. This is most certainly a dangerous volcano on the island. Having last erupted in the 1960s-1970's, and causing many fatalities as pyroclastic flows moved quickly over the caldera lake's surface to the shores, the volcano has since been showing fluctuations and signs of D/I (Deflation/Inflation) events. The temperature of the central caldera cone's lake has risen and fallen, acidity levels have fluctuated, and GPS shows many deformation events. It is likely that within the next decade or two, Taal will erupt again.

As it stands currently, no alert levels have been raised for any currently active volcanoes in the Philippines after the quake, and there is no imminent risk of eruption.

The Philippines archipelago lies along the so-called Pacific Ring of Fire, which encircles the entire Pacific ocean plate. The majority of the worlds large earthquakes and active volcanoes occur along this ring, which spans form the West Coast of the Americas, to Russia's Kamchatka and Kurile Islands, to Japan, to the Philippines, to Indonesia, and New Zealand.

Shallow Ongoing Quake Swarm near Pisgah Crater, CA

Over the last several days there has been an ongoing quake swarm near California's Pisgah Crater in the Lavic Lake Volcanic Field. Magnitudes have ranged from less than 1.0 up to 4.3, and most are occurring at very shallow depths. While this may alarm some due to the proximity to the monogenetic Pisgah Crater, these quakes are purely tectonic and not volcanic in nature. The depths are far too shallow to be related to magma, unless there was already an eruption underway (which there is not).

The quakes however are close enough to the system to have an effect (if say, there was a magma chamber still laying around underneath the crust, which is a bit doubtful at this time).

Image of the Pisgah Crater area with the location of the quakes. Screenshot from Google Earth with USGS plugin. 

While normally I wouldn't even bother writing about this volcano (as it has not erupted in historical time, nor will it likely erupt int he near future), there has been some un-needed and unjustified hype about it due to some alarmist bloggers, namely some anonymous 'blogger' named "Dutchsinse", who regularly raises false alarms about this volcanic system. I can assure you, there is nothing now, or in the recent past, that suggests that this system is currently active at all. If in fact there was any reason for concern in the near future, you can rest assured that the USGS would absolutely be able to tell far in advance if magma was rising, and since we are talking about California, media coverage would be incredibly heavy.

In any case, earthquake swarms near the San Andreas fault are quite common, and California is criss-crossed by many other smaller faults with regular small to moderate activity. This is absolutely nothing new.

The area is however a beautiful place to visit if you have the time and the drive to go out that way, and it is certainly a cool sight to see 'fresh' looking lava flows much like you'd find in Hawaii's Kilauea volcanic system. If you'r in the area (or are ready for a read trip to basically nowhere) you can easily check out Pisgah Crater, and nearby Amboy crater, both of which are morphologically fresh and well-preserved monogenetic cinder cones. Monogenetic cones only erupt once, and typically never again.

If a new eruption were to occur at Lavic Lake, it would likely not be in the same location that it had erupted in before, and would create a new vent or vents.

7.0 Magnitude Quake Strikes Peru, Tsunami Warning Issued

A 7.0 magnitude quake has occurred along the subduction zone in northern Peru, along the Pacific Ring of fire. Nearby Holocene volcanoes are Sara Sara, Coropuna, Andahua-Orcopampa, Huambo, and Sabancaya. The nearest volcano is Sara Sara, which last had an eruption during the Holocene, but historical eruptions are uncertain at best. Ash layers in peat moss do suggest somewhat geologically recent activity. The nearest historical volcano is Andahua-Orcopampa, which according to the GVP had its last eruption in the early 15th century. Sabancaya has also shown recent unrest, but is pretty far from the epicenter.

The tremblor prompted officials to issue a tsunami warning for the South Pacific, which is probably out of an abundance of caution, rather than because a tsunami was generated.

Damage has been reported in nearby towns, however no deaths or injuries are yet apparent. 

Screenshot of Google Earth with USGS overlay, and shakemap.

Earthquakes of large magnitude are common in the region, and along the majority of the subduction zones of the Pacific Ring of Fire. Peru typically has several large quakes a year, as well as Chile, which had a magnitude 8.8 quake several years ago that created a small tsunami. By the time the tsunami reached the big island of Hawaii, it was only a couple of feet (if that) high, and created very little damage apart from knocking a few boats around. The tsunami from the 2011 Japan quake, in contrast, was generated by a magnitude 9.0 subduction quake, which was able to cause damage as far as Southern California in the US.

A 7.0 earthquake is unlikely to generate a significant tsunami.

7.7 Magnitude Quake Hits Pakistan

A very large and relatively shallow quake has hit Pakistan today, causing a lot of damage, and fatalities. The quake struck near the country's southern shore, near the town of Parwān, about 173 miles NW of Karachi. The quake was strong enough to be felt throughout the region from India, to Afghanistan, to South Eastern Iran.

Image of quake epicenter from Google Earth with USGS plugin.

The quake occurred along a meandering strike-slip type fault, which has the potential, much like California's San Andreas fault, to generate large quakes up to and possibly exceeding 8.0 in magnitude.

So far at least 5 fatalities have been reported, as well as damage to buildings in the area.

Image of the quake 'shakemap' (legend is at the top of the screen) detailing the strength of the quake in relation to its epicenter.

At this time, at least 5 large-ish aftershocks have struck NNE of the epicenter, ranging from magnitude 4.7 to 5.9. More aftershocks are likely to hit the area for a period of several days to several weeks.

It is also likely that the list of injured or dead may increase as more information becomes available. The area where the quake struck is remote with several large villages nearby, but no major cities, and this is the area where the shaking was most intense. If any significant updates develop, I will update this post.


*****UPDATE*****

The quake was apparently powerful enough to cause some land to uplift, and a 30-40ft high island was actually created off of the coast due to the uplift! The island is around 100 feet long, and about one mile off of the coast.

We also know now that the quake has unfortunately killed around 250 people. (correction, the toll is now at around 330 people, and there are approximately 445 injured at this time)... The area is populated densely, but the buildings are not modern in any sense of the word, some being made of stones and mortar.

7.0, 6.8 Quakes Strike Alaska's Aleutian Islands

A 7.0 Quake struck SE of Adak island in Alaska's Aleutian islands today, according to USGS. The quake was followed by several aftershocks, one of mag 6.6 in the immediate vicinity, and followed to the East by a 6.8 magnitude tremor. More aftershocks are likely to occur for a few days.

Google Earth/USGS image of quake location.

The initial 7.0 quake was at a depth of approximately 21.4mi. No tsunami was generated according to USGS/NOAA. This occurred along the Aleutian subduction zone, where larger quakes are quite common.

There are no major population centers near the earthquake epicenter, with the nearest populated location being Adak, a port city that serves fisherman/crabbers in the Bering Sea. No damage has been reported.