Downgoing plate topography stopped rupture in the A.D. 2005 Sumatra earthquake

Earthquakes in subduction zones rupture the plate boundary fault in discrete segments. One factor that may control this segmentation is topography on the downgoing plate, although it is controversial whether this is by weakening or strengthening of the fault. We use multichannel seismic and gravity data to map the top of the downgoing oceanic crust offshore central Sumatra, Indonesia. Our survey spans a complex segment boundary zone between the southern termination of the Mw = 8.7, A.D. 2005 Simeulue-Nias earthquake, and the northern termination of a major 1797 earthquake that was partly filled by an Mw = 7.7 event in 1935. We identify an isolated 3 km basement high at the northern edge of this zone, close to the 2005 slip termination. The high probably originated at the Wharton fossil ridge, and is almost aseismic in both local and global data sets, suggesting that while the region around it may be weakened by fracturing and fluids, the basement high locally strengthens the plate boundary, stopping rupture propagation

DIFRAKSI DAN EFEK SMILING PADA DATA SEISMIK

AbstrakDifraksi dan efek smiling merupakan artefak yang sering terdapat pada data seismik. Difraksi timbul pada data sebelum dilakukan proses migrasi sedangkan efek smiling timbul setelah dilakukan proses migrasi. Dalam penelitian ini akan dibahas efek smiling pada penampang hasil migrasi yang pada wilayah tersebut merupakan tempat terjadinya difraksi sebelumnya. Kata Kunci: Difraksi, Efek Smiling, MigrasiAbstractDiffraction and smiling are the two effects that often present in a seismic data. Diffraction occurs before the migration process, while the smiling occurs after the migration process. This research will discuss the effect of smiling on a cross section of the result of migration, which is the diffraction happened in an area of investigationKeywords: Diffraction, Smiling Effect, Migratio

Seismic images of the megathrust rupture during the 25th October 2010 Pagai earthquake, SW Sumatra: Frontal rupture and large tsunami

The Mentawai segment of the Sumatra subduction zone is locked and likely to produce a large earthquake in the near future. A part of this locked zone ruptured on 12 September 2007 producing twin earthquakes of Mw = 8.5 and 7.9. Recently, a third earthquake of Mw = 7.8 occurred on the 25th October 2010, SW of Pagai Island, Sumatra. The earthquake generated an unexpected very large tsunami on Pagai Islands with run‐up height of up to 8 m. Here we present seismic reflection and bathymetry images from the 2010 epicentral region acquired before the earthquake. We find that the frontal thrust is the main active fault in this region and might have ruptured up to the seafloor at 6 km water depth uplifting the water column and producing a large tsunami. Furthermore, finite fault models indicate that this earthquake ruptured the frontal section of the subduction zone, which is generally believed to slip aseismically and be incapable of producing large earthquakes. The presence of aftershocks near the subduction front further confirms that the frontal section of the subduction zone is not aseismic. If the rest of the Mentawai locked zone ruptures the frontal section of the subduction zone during a megathrust, then the resulting tsunami in the Indian Ocean could be devastating

Simple Statistical Testing on Existing Data of Core 39 KL SO189/2 to Reveal its Correlation Towards Sea Surface Temperature Variation

Several paleotemperature proxies using marine core sediment data have been developed and well-proven, but they need excellent laboratory handling and destructive tools. Spectrophotometer and Multi-Sensor Core Logger (MSCL) is considered rapid and non-destructive tools compared to other climate proxies. This paper enhances the correlation between existing data of spectrophotometer, MSCL, and sea surface temperature (SST) of the sediment core 39 KL from SO189/2 through a statistical test. The dataset is processed using interpolation, Pearson correlation, and K-means clustering. Pearson correlation reveals a strong correlation between spectrophotometer, MSCL, and SST. K-means clustering points out that SST is shifting from relatively colder to warmer. This study also tries to understand the source of four tephra and one terrigenous layer. It can be concluded that the spectrophotometer and MSCL have a positive correlation to SST variation. Keywords: statistical approach, existing data of SO189/2, spectrophotometer, Multi-Sensor Core Logger, sea surface temperatureBeberapa proksi paleotemperature menggunakan sedimen inti laut telah dikambangkan dan terbukti baik, namun membutuhkan penanganan laboratorium yang bagus dan bersifat destruktif. Spektrofotometer dan Multi Sensor Core Logger (MSCL) relatif lebih cepat dan tidak destruktif. Makalah ini membahas hubungan antara spektrofotometer, MSCL, dan temperature muka laut (SST) berdasarkan data sedimen inti 39 KL dari SO189/2 melalui pendekatan statistik. Data diolah menggunakan metode interpolasi, korelasi Pearson, dan kluster K-means. Korelasi Pearson menunjukkan korelasi kuat antara spektrofotometer, MSCL, dan SST. Kluster K-means menunjukkan pergeseran SST dari kondisi yang lebih dingin ke lebih hangat hubungan Stufi ini juga mencoba untuk memahami sumber 4 lapisan tefra dan 1 lapisan mineral terrigenous. Melalui studi ini, dapat disimpulkan bahwa spektrofotometer dan MSCL mempunyai korelasi positif terhadap variasi SST.Kata Kunci: Pendekatan statistik, Data existing SO189/2, spektrofotometer, Multi Sensor Core Logger, Suhu Permukaan Lau