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7.0 Earthquake S Of W Java Coast  
User currently offlineBaroque From Australia, joined Apr 2006, 15380 posts, RR: 59
Posted (5 years 2 weeks 4 days 8 hours ago) and read 1534 times:

http://earthquake.usgs.gov/eqcenter/...qsww/Quakes/us2009lbat.php#details

It appears that some communications have been interrupted. The nearest large town is Tasikmalaya, but it was quite close to Bandung.

In Bandung, I had it on good authority (SWMBO) that folk left the houses rather sharpish. But current accounts suggest little damage.

Apparently Jakarta got quite a shake. It is much further away, but largely sits on alluvium which is never a good "look" during earthquakes.

For location is is inboard of the plate boundary. Usually earthquakes on the Benioff zone would be a bit deeper than the 30.8 miles reported by the USGS so maybe it relates like the Yogya quake to a fracture in the upper plate.

Any news from Indonesian a.net members? Hope you are all OK. Some of those coastal towns West of Cilacap might have had some problems. The prisoners near Cilacap must have thought is was a version of the last trump!

18 replies: All unread, jump to last
 
User currently offlineMadameConcorde From San Marino, joined Feb 2007, 10897 posts, RR: 37
Reply 1, posted (5 years 2 weeks 4 days 8 hours ago) and read 1527 times:

My Earthquake map says a 7.4 earthquake.
I saw it. This is a very powerful earthquake. It probably shook a lot of buildings in Jakarta.

There is a lot of volcanic activity in Java and Bali and all around there. I hope not too big a numbber of casualties.

I look at this map every day.

http://hisz.rsoe.hu/alertmap/index2.php



There was a better way to fly it was called Concorde
User currently offlineBaroque From Australia, joined Apr 2006, 15380 posts, RR: 59
Reply 2, posted (5 years 2 weeks 4 days 7 hours ago) and read 1522 times:



Quoting MadameConcorde (Reply 1):
My Earthquake map says a 7.4 earthquake.

As far as I can work it out, the initial USGS interpretation was 7.4 and our ABC reported it as that, but by the time I got up to this computer, the USGS had revised it to 7.0 and tbe BEEB reports this too.

Some buildings collapsed in Tasik, some building damage reported in Bandung, but herself reports no damage in her area of Bandung. It certainly shook Jakarta. Bandung too has some thick alluvium so we should wait to see what happened in the S of the city. One good point is that the rains have not yet started so the alluvium would be dry in relative terms at least and therefore less likely to become thixotropic.

The epicentre is a fair way S of the southern line of volcanoes so initially you would not expect any effects. However, Galunggung is close to Tasik, so I dare say Vulcanology Dir will be keeping an eye on that mountain for a while. Tangkuban Perahu overlooks Bandung, is active and lies on some major fault lines, so they will probably keep an eye on it too - well they always do come to that. An earlier Direktor of Vulcanology told me the nearest analogue to Tangkuban Perahu is - Kratatoa - oh dear as I said to him at the time!!


User currently offlineBaroque From Australia, joined Apr 2006, 15380 posts, RR: 59
Reply 3, posted (5 years 2 weeks 4 days 2 hours ago) and read 1471 times:

Partial update. 12 dead in Tasik, presumably more to the S of Tasik. Also some reported dead in Bandung, but not sure, phones seem to be cut, SMS only.

Electricity out for some time in the western part of Bandung.

If not posting, would Indonesian members IM me.


User currently offlineWarRI1 From United States of America, joined Sep 2007, 8908 posts, RR: 10
Reply 4, posted (5 years 2 weeks 4 days 1 hour ago) and read 1460 times:



Quoting MadameConcorde (Reply 1):
I look at this map every day.

Let us hope for the best, I thank you for the site information, very interesting.



It is better to die on your feet, than live on your knees.
User currently offlineBaroque From Australia, joined Apr 2006, 15380 posts, RR: 59
Reply 5, posted (5 years 2 weeks 3 days 14 hours ago) and read 1414 times:

Sadly death toll rising. Phone contact to Bandung extremely difficult, now even SMS messages seem to be queued or in some way delayed.

http://news.bbc.co.uk/2/hi/in_pictures/8234074.stm

Shows some of the damage and for those curious about housing structures some common types of home construction. The collapse of the roof where the walls seem OK is explained by the very light timbers used in most roof structuresa and the use of reinforcement in pillars used in building the walls. The tiles shown in the first picture are extremely light (by Australian standards) and the wood holding them up tends to be less than 2 cms in thickness. Don't forget that most timber for housing is sawn on site, not much pre-cut material around.

It really IS a different world.

Landslide at Cianjur - at least our ABC are now pronouncing this correctly as Chianjur and not Ceeanjur. Ci, or Chi in Sunda mean to do with water or river. With all the Cimahis, Cibabat and Cianjurs around, it is indeed a wet place when it rains. 10 reported dead there and 41 missing.

It will be a while before reliable information comes on damage along the S coast. Tasik seems to be badly damaged.


User currently offlineAfterburner From Indonesia, joined Jun 2005, 1211 posts, RR: 1
Reply 6, posted (5 years 2 weeks 3 days 13 hours ago) and read 1408 times:

The death toll has risen to 45. More than 18,000 houses and buildings have been destroyed or at least damaged.

I was working in my room on the third floor when it happened. It was the strongest earthquake I've ever experienced. It caused some cracks to appear on the walls of my house. Some high-rise office buildings have broken windows and/or cracked walls because of this earthquake.


User currently offlineBaroque From Australia, joined Apr 2006, 15380 posts, RR: 59
Reply 7, posted (5 years 2 weeks 3 days 10 hours ago) and read 1391 times:



Quoting Afterburner (Reply 6):
the strongest earthquake I've ever experienced

Yes, herself had not experienced anything like that in forty years. It is possible that the ground effects in Jakarta were worse than in Bandung due to the alluvium. Is your house on alluvium? Then again, even under the alliuvium is soft sediment near Jakarta until you get to Bogor. Check on your roof. Do you have reinforced concrete posts in the walls?

Hope that is that for this bit of activity. The USGS has just one aftershock and quite small.

Stay safe.


User currently offlineMandala499 From Indonesia, joined Aug 2001, 6858 posts, RR: 75
Reply 8, posted (5 years 2 weeks 3 days 3 hours ago) and read 1371 times:

It's 7.3 according to the govt., 7.4 according to USGS... then revised...
Whichever...

Yesterday when it happened, the phone connections to Tasik area were cut off for at least an hour... mobile phones network jammed for a bit too...

My house and Afterburner's are in South Jakarta... it's a bit rockier than the other parts of Jakarta. I did a full inspection check on 2 family houses yesterday, no damage found, but one was recently renovated with a few questions left (added a new floor)... so I hope everything will hold out fine.

Let's just say afternoon traffic yesterday was ATROCIOUS! One of the worst I've seen... I took a motorbike to check the other house because I know traffic would be a total nightmare... even then I was gridlocked... thank God I didn't use the car yesterday... would have been a total waste of fuel... what normally took 10 mins by motorbike/15 - 20 by car, and max 45 mins by car in rush hour, took be a good friggin' hour and a bit by bike, with looooong gridlock stops...

I was working at home when it happened. First felt a quick passing shockwave... then the dogs barked... the word earthquake immediately came to my mind, and remembered some were working fixing the roof tiles... ran out told them "earthquake"... as soon as I completed the word... the terrestrial phugoid motion began, and it was stronger than the ones before, but slower and seemingly larger amplitude... Shallow and some distance was what came to the mind... The pool immediately began it's "mini tsunami"... took a video of it... but after about 45 seconds into the quake, the shaking got pretty bad... (real large long slow motion)... freaked me a bit. After about 90 - 120 seconds it stopped...
the pool lost about 15 - 20cm's worth of water depth...

Then several aftershocks... one was quite strong for an aftershock (5.1 they said)...

The characteristics of the oscillation got me worried about the other house.

Seeing the water spill pattern (ie: pool shape, orientation and where the sides dry patches are), quickly pointed at the Garut/Tasik/Pamengpeuk area...

Anyways, this one was different from the ones felt before.

I'll post the video laters when I got time... still recovering from the traffic yesterday  Smile



When losing situational awareness, pray Cumulus Granitus isn't nearby !
User currently offlineBaroque From Australia, joined Apr 2006, 15380 posts, RR: 59
Reply 9, posted (5 years 2 weeks 3 days 3 hours ago) and read 1368 times:

Welcome back M, your absence was noted!!!

Quoting Mandala499 (Reply 8):
Let's just say afternoon traffic yesterday was ATROCIOUS! One of the worst I've seen... I took a motorbike to check the other house because I know traffic would be a total nightmare... even then I was gridlocked... thank God I didn't use the car yesterday... would have been a total waste of fuel... what normally took 10 mins by motorbike/15 - 20 by car, and max 45 mins by car in rush hour, took be a good friggin' hour and a bit by bike, with looooong gridlock stops...

At least that gives me a laugh. One of the clips shown by the TV is of traffic down a road, could be Sudirman, but it looks a bit like any old afternoon and there is absolutely NO explanation, not in English or in Indonesian or subtitles - nuthin. So nice to know what THAT was about.

Quoting Mandala499 (Reply 8):
Seeing the water spill pattern (ie: pool shape, orientation and where the sides dry patches are), quickly pointed at the Garut/Tasik/Pamengpeuk area...

We should write to USGS and they might hire you and your pool to work out first motion directions!!!

Herself is back on SMS type air and reports quite a bit of damage in other parts of Cimahi. Two dead either in Lembang or Bandung, not clear, but significant numbers of houses officially classified by her as "rusak" which could mean some damage or totally flat I guess depending how optimistic she is feeling.

Your guys were lucky they got off the roof, then again if the roof fell, they might have been marginally better off on top than underneath!! Usual type of roof??

The USGS seem fixed on their 7.0 revision, but I notice that in Indonesia it is still at 7.4 or 7.3, more dramatic I guess. One way and another seems to have been dramatic enough at whatever it was!!

Look forward to the videos.


User currently offlineMandala499 From Indonesia, joined Aug 2001, 6858 posts, RR: 75
Reply 10, posted (5 years 2 weeks 3 days ago) and read 1360 times:



Quoting Baroque (Reply 9):
We should write to USGS and they might hire you and your pool to work out first motion directions!!!

Well it was either the correct area, or the other way, which would be somewhere in the eastcoast of Sumatra, which wouldn't make sense at all...

When it was the Indramayu quake, I thought it was from Ujung Kulon based on the pool!  Smile

Quoting Baroque (Reply 9):
Your guys were lucky they got off the roof, then again if the roof fell, they might have been marginally better off on top than underneath!! Usual type of roof??

Old heavy wood... they're at least 10x20cm in thickness... The quake damage risk isn't the roof collapsing onto itself, but for the walls to give way to the heavy roof structure, but architects and engineers assessing this house has said, it'll take a scale 7-8 with an epicenter that's very close for that to occur... Comforting? Not really... nice to know... not really...

Those guys jumped to the water tower and slid down ! LOL

Quoting Baroque (Reply 9):
Look forward to the videos.

Well, don't expect too much!  Smile



When losing situational awareness, pray Cumulus Granitus isn't nearby !
User currently offlineComorin From United States of America, joined May 2005, 4896 posts, RR: 16
Reply 11, posted (5 years 2 weeks 2 days 19 hours ago) and read 1352 times:

Hi Baroque, a question:

Does the Richter scale compensate for depth? In other words, is a 7.1 quake 10 km deep feel the same as a 7.1 closer to the surface? Any explanations on how to interpret this measurement appreciated!

Thanks

Comorin


User currently offlineBaroque From Australia, joined Apr 2006, 15380 posts, RR: 59
Reply 12, posted (5 years 2 weeks 2 days 13 hours ago) and read 1330 times:



Quoting Comorin (Reply 11):
Hi Baroque, a question:

Does the Richter scale compensate for depth? In other words, is a 7.1 quake 10 km deep feel the same as a 7.1 closer to the surface? Any explanations on how to interpret this measurement appreciated!

Prefaced by definitely NOT my field, but as best I can, the Richter Scale measures (or is intended to measure) the amount of energy released by a quake.

So if a given amount of energy is 7 in a near surface quake, it is still 7 at 120 km deep. As you suggest, the second case would show much LESS energy at the SURFACE.

Actually where Mandala lives and where my wife's house is does have quite common quakes up around 6 or so but deep on the Benioff zone, so over 100 kms under Bandung and even deeper under Jakarta as the Benioff Zone dips steeply to the N.

The nasty bit about this weeks quake and the one at Yogya is that they seem to have occurred at the thin edge of the overlying plate as the Indian Ocean plunges under Java. Had they been on the Benioff Zone itself they would have been further out or deeper and in both cases much less destructive.

The Richter is a log scale (base 10) so the 7.4 reported at first would have been a HELL of a lot stronger than the 7.0 that USGS seems to have settled on.

There is a more recent "moment magnitude scale" that measure the same property and give similar values.

For those who measure things by bombs, a Nagasaki bomb, exploded underground would give a shock of about 5. Which of course is why underground testing was easy to detect. So Mandala' pool was discombobulated by about 32 megatons of TNT being let off down S of Java.

Numbers from Wiki (or course).


User currently offlineComorin From United States of America, joined May 2005, 4896 posts, RR: 16
Reply 13, posted (5 years 2 weeks 2 days 5 hours ago) and read 1315 times:



Quoting Baroque (Reply 12):

Thank you for the detailed explanation, Baroque! I also read with interest about Mandala's shaking pool. Perhaps he was going through a 'Eureka' moment about AF332!

I have only experienced one earthquake and it is quite terrifying. My thoughts are with the people of Java.


User currently offlineBaroque From Australia, joined Apr 2006, 15380 posts, RR: 59
Reply 14, posted (5 years 2 weeks 2 days 4 hours ago) and read 1310 times:



Quoting Comorin (Reply 13):
Quoting Baroque (Reply 12):

Thank you for the detailed explanation, Baroque! I also read with interest about Mandala's shaking pool. Perhaps he was going through a 'Eureka' moment about AF332!

He probably did have flashes of pitot tubes before the eyes as the water sloshed up!!  bigthumbsup 

Quoting Comorin (Reply 13):
I have only experienced one earthquake and it is quite terrifying. My thoughts are with the people of Java.

We have had about four or five smallish ones, nothing like that. But my best story is of the night I was giving a lecture - 6 pm to 7 pm (apparently on 8 Mar 1973) and in Geol 1 had got to the general bit about earthquakes and commented on the difference between quake frequency in less stable settings such as Indonesia and the W Coast of the US. And I duly pointed out that Aus was generally a stable region and the Sydney Basin while it had a few quakes was also stable in relative terms. But (CLOSING SENTENCE) that did not mean there could not be an earthquake here, in fact there could be one tonight. (Shuts file and walks off at end of lecture.)

Went to bed and about 05.09+ was just about knocked out of bed. After thinking half the house had fallen down - we were having alterations done at the time - I had just worked out it was a quake when the phone rang and on the other end was the Dept Geophysicist practically doing a dance of joy!! But the students were vastly impressed by the lucky guess.


User currently offlineComorin From United States of America, joined May 2005, 4896 posts, RR: 16
Reply 15, posted (5 years 2 weeks 1 day 15 hours ago) and read 1302 times:



Quoting Baroque (Reply 14):
We have had about four or five smallish ones, nothing like that. But my best story is of the night I was giving a lecture - 6 pm to 7 pm (apparently on 8 Mar 1973) and in Geol 1 had got to the general bit about earthquakes and commented on the difference between quake frequency in less stable settings such as Indonesia and the W Coast of the US. And I duly pointed out that Aus was generally a stable region and the Sydney Basin while it had a few quakes was also stable in relative terms. But (CLOSING SENTENCE) that did not mean there could not be an earthquake here, in fact there could be one tonight. (Shuts file and walks off at end of lecture.)

Went to bed and about 05.09+ was just about knocked out of bed. After thinking half the house had fallen down - we were having alterations done at the time - I had just worked out it was a quake when the phone rang and on the other end was the Dept Geophysicist practically doing a dance of joy!! But the students were vastly impressed by the lucky guess.

That must have sealed your reputation with many a geologist-to-be! Great story, thanks for sharing. I wonder what the chances of a quake here in NYC are,,, zero?  Wink

I suppose most earthquakes still take place in the Ring of Fire...I did note on a map that the Himalayas are also quite active.


User currently offlineBaroque From Australia, joined Apr 2006, 15380 posts, RR: 59
Reply 16, posted (5 years 2 weeks 1 day 10 hours ago) and read 1292 times:



Quoting Comorin (Reply 15):
That must have sealed your reputation with many a geologist-to-be! Great story, thanks for sharing. I wonder what the chances of a quake here in NYC are,,, zero?

Not great but there is a structure just S of NYC that is a bit active, would have to look at maps to figure exactly where. But even the most stable of blocks will "creak" at times.

Quoting Comorin (Reply 15):
I suppose most earthquakes still take place in the Ring of Fire...I did note on a map that the Himalayas are also quite active.

The ring of fire, but all the major compressions zones, so the Himalayas, round through Afghanistan up through the Zagros mountains to Turkey and then up through the former Yugo to the Alps. The Alps are a bit more quiet than you would expect. But the Appenines are a pretty active compression zone too.

In the US the W seaboard obviously. But then there is the Mis embayment where the New Madrid quake happened, but that "should be" a tensional setting. However some compression seems to be present as well.

With Jawa, the Indian plate is slipping under Java more or less at right angles to the coast and MOSTLY, the plane of slip does not seem to store much energy and most quakes are deep under Java and not a problem. This one was different.

With Sumatera, the coast head more NW, so the plate movement is oblique. That seems to allow more settings for energy storage. It also means that onshore, along a depression in the mountain range, Bukit Barisan, there is the Trans-Sumatera Fault. Very nasty. Quakes intense and shallow, caused by energy transmitted from the nearby plate boundary, but being released within the upper plate rocks.


User currently offlineFCA767 From United Kingdom, joined Nov 2006, 1763 posts, RR: 1
Reply 17, posted (5 years 2 weeks 1 day 9 hours ago) and read 1287 times:



Quoting MadameConcorde (Reply 1):
I look at this map every day.

Thanks for that info...I like the map  Smile


User currently offlineBaroque From Australia, joined Apr 2006, 15380 posts, RR: 59
Reply 18, posted (5 years 2 weeks 1 day 8 hours ago) and read 1281 times:



Quoting Comorin (Reply 15):
I wonder what the chances of a quake here in NYC are,,, zero? Wink

This link should get your attention as the pic has NY in the background!

http://www.geo.hunter.cuny.edu/bight/newark.html

But the Newark Trough is pretty dead seismically, but you can see there are plenty of faults that could let go. The thing is that with those faults, it is the more minor within plate shuffles that will cause them to let go, whereas with Jawa, the Indian ocean plate is ALWAYS pushing under at about the same rate as your finer nails grow, or just a bit faster!

A more general paper on US quakes is at

http://www2.bc.edu/~kafka/Why_Quakes/why_quakes.html


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