{"id":7350,"date":"2018-05-04T23:06:36","date_gmt":"2018-05-05T07:06:36","guid":{"rendered":"http:\/\/earthjay.com\/?p=7350"},"modified":"2024-05-04T22:14:00","modified_gmt":"2024-05-04T22:14:00","slug":"earthquake-volcanic-eruption-report-hawaii","status":"publish","type":"post","link":"https:\/\/earthjay.com\/?p=7350","title":{"rendered":"Earthquake-Volcanic Eruption Report: Hawai’i"},"content":{"rendered":"

My USGS Earthquake Notification Service email inbox has been going on overtime.<\/p>\n

There has been a swarm of earthquakes on the southeastern part of the big island, with USGS volcanologists hypothesizing about magma movement and suggesting that an eruption may be imminent. Here is a great place to find official USGS updates on the volcanism in Hawaii<\/a> (including maps). I had been following this on social media.<\/p>\n

Here is a temblor blogpost that I wrote<\/a>. Here is a Spanish version<\/a>.<\/p>\n

Hawaii is an active volcanic island formed by hotspot volcanism. The Hawaii-Emperor Seamount Chain is a series of active and inactive volcanoes formed by this process and are in a line because the Pacific plate has been moving over the hotspot for many millions of years.<\/p>\n

As these volcanoes grow with time, the flanks of the volcanoes become covered in new volcanic rock. The flanks become unstable and collapse as landslides. There is evidence that some of these landslides trigger some of the largest tsunami ever found.<\/p>\n

The seismicity started in the central part of the “East Rift Zone” (ERZ), a region of extension probably caused by flank collapse. This extension lowers pressure in the magma chamber, leading to eruptions. Magma migrates around for various reasons, including changes in pressure in the magma chamber. These motions of magma and fluids can cause earthquakes.<\/p>\n

This part of Hawaii is the locus of the most recent volcanism, with the newest volcanic center formed to the southeast of the island.<\/p>\n

Southeast of the main Kilauea vent, the Pu\u2018u \u2018\u00d6\u2018\u00f6 crater saw an elevation of lava into the crater, leading to overtopping of the crater (on 4\/30\/2018). Seismicity migrated eastward along the ERZ. This morning, there was a M 5.0 earthquake in the region of the Hilina fault zone (HFZ). I was getting ready to write something up, but I had other work that I needed to complete. Then, this evening, there was a M 6.9 earthquake between the ERZ and the HFZ.<\/p>\n

There have been earthquakes this large in this region in the past (e.g. the 1975.1.29 M 7.1 earthquake along the HFZ). This earthquake was also most likely related to magma injection (Ando, 1979). The 1975 M 7.1 earthquake generated a small tsunami (Ando, 1979). These earthquakes are generally compressional in nature (including the earthquakes from today).<\/p>\n

Today’s earthquake also generated a tsunami as recorded on tide gages throughout Hawaii. There is probably no chance that a tsunami will travel across the Pacific to have a significant impact elsewhere.<\/p>\n

So. This M 6.9 may be the largest earthquake. There may be a larger one in store (the USGS suggests that these fault systems could produce a M 8 earthquake). The eruptions may be done for now. There may be more.<\/p>\n

Below is my interpretive poster for this earthquake<\/font><\/h2>\n

I plot the seismicity from the past month, with color representing depth and diameter representing magnitude (see legend). I include earthquake epicenters from 1918-2018 with magnitudes M \u2265 4.5 in a second poster (and down to M \u2265 3.5 in a third poster).
\nI plot the USGS fault plane solutions (moment tensors in blue and focal mechanisms in orange) for the M 6.9 earthquake, in addition to some relevant historic earthquakes.
\nI placed green circles in the locations of the (a) 4\/30 lava lake filling event and (b) 5\/3-4 fissure eruption.<\/p>\n