tulisanes on March 2, 2017 at 11:42 am
WMT, i got ahold of that xerox copy of faultlines in 199O, which i kept and rediscovered about 10 years later; then realizing we had more powerful computers than the XT PCs running on DOS a decade back, and my office had a scanner and a book-bound map of metro manila; meshing curiosity with new-found skills in photoshop, i scanned the metro maps and the phivolcs map and assembled their files and overlay the latter on the former. to my shock and surprise, i discovered the west valley fault ran right smack under MY HOUSE! what chances might that happen to someone who pieces together an earthquake map for more than a nerve-wracking month –fours hours daily– as a weird hobby? for a long time i was in disbelief. then i realized it was my epiphany: a surreal revelation that this was my MISSION IN LIFE …which to date culminated in the metro manila wide campaign some years back to save and alert SCHOOLS and communities that are in the destructive path of the west valley fault (thanks to an influential follower of this blog who triggered an avalanche of awareness).
I digress. Back to your post…
No, no faultline along Marcos Hiway from Ligaya to Cogeo. But beyond Cogeo, over the top and behind Sun Valley, there are two faultlines there that Phivolcs is not naming (thus, i adopt and christen them the TULISANES FAULTLINES –nice ring to it, eh?).
Again, i digress. These two faults intersect in Montalban at the point where the ABANDONED Wawa Dam lies (funny the mountain that split right where the river flows nurses the Bernardo Carpio legend. This giant was apparently trapped inside the mountain, and he pushed it apart creating a river flow and causing an EARTHQUAKE while doing it. An earthquake: coincidence?
Now what is the significance if these two faultlines? Now children, gather round and listen to a scary story.
When the west valley fault was formed, the land mass BROKE off and dropped thus creating a VALLEY. But has it ever occured to anyone that when one end dropped, the opposite end while it did not drop, broke off and may just be hanging precariously by a thread? Imagine a corner roof of a house, specifically the “medya agua” that is usually bordered by rain gutter. Imagine at the height of a typhoon, amid howling wind, this corner roof broke off, fell –but not totally– and hangs precariously just by a thread. THIS is the picture of the west valley fault, where one point is lower. But a very powerful quake can dislodge and totally break off the hanging “roof corner” and the entire “medya agua” falls! By high magnitude earthquake, this can mean SEVERAL TENS OF FEET of land drop (whether slow or sudden, only God knows)! No wonder the “red patch” i point out in the new Phivolcs study gets the most number and degree of damages and toll on human life and property!