Of the 14 SSBNs currently in the fleet, two are normally in overhaul at any given time. Of the remaining operational 12 submarines, 8-9 are deployed on patrol at any given time. Four of these (two in each ocean) are on “Hard Alert” while the 4-5 non-alert SSBNs can be brought to alert level within a relatively short time if necessary. One to three SSBNs are in refit at the home base in preparation for their next patrol. This is what I was getting at, I do know the difference from hard alert (subs launch ready missiles pre-targeted) to just deployed this has directly to deal with the fact that we shut down our ELF transmitter in WI. Only the Hard Alert subs are shallow enough or streaming a VLF buoy the others are deep and silent hiding for a second strike, with the old ELF bell ringer all the subs could be deep and silent listening to ELF waiting for the balloon to go up ready to loft their birds. In 1995 SLBM Strategic Retargeting System (SRS) was approved. D-5s can be rapidly re-target to any spot in the world. We offloaded some MIRVS from our D5's which greatly increases there range, like I said boats in port in WA & GA can hold China at risk we have tested surface launching SSBM's successfully in the past and one of the crews is always with the sub even in port unless its undergoing midlife retrofit. If China starts saber rattling you can bet all 8-9 boats will be on hard alert. The D5 as deployed has a range of 12000km this is the area of the globe a D5 SSBN can be in to hit Beijing. you will notice that both WA and GA are with in the circle as is most of the northern hemispheres oceans only the southern oceans by south America are out of range and we can assume not many Trident boats are down there holding Brazil at risk. 
Ultimately, in it’s current configuration, only 4 USN boomers would be in range to launch against China on short notice(within 10-20 min). And for this to even be possible, we are assuming 4-5 MIRVs per Trident. Upping the payload on each D5 to 12 MIRVs would decrease the number of hard alert subs within striking range at any given time.
I’m discounting the 2nd strike capabilities of the SSBN fleet because China would never strike first in the current strategic calculus(what with it’s numerical disadvantage in warheads). And also because, China’s land-based ICBM capability has a response time of 10-20 min. So by the time the 2nd strike SSBNs are in position to launch, the initial nuclear exchange would’ve already happened.
So still, we are talking about 96 missiles, 4-5 MIRVs each => 384-475 warheads against China in a first strike.
If one keeps in mind, that China can retaliate within 10 minutes of launch detection with 150-160 warheads on the conus directly, and another 200-300 against U.S bases and allied nations in the Pacific. It becomes clear that initiating any kind of nuclear blackmail with China is extremely risky at this stage.